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Network Working Group                                    J. Reschke, Ed.
Internet-Draft                                                greenbytes
Intended status: Standards Track                                S. Reddy
Expires: January 8, 2009                                          Mitrix
                                                                J. Davis

                                                               A. Babich
                                                                     IBM
                                                            July 7, 2008


        Web Distributed Authoring and Versioning (WebDAV) SEARCH
                     draft-reschke-webdav-search-16

Status of this Memo

   By submitting this Internet-Draft, each author represents that any
   applicable patent or other IPR claims of which he or she is aware
   have been or will be disclosed, and any of which he or she becomes
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   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on January 8, 2009.

Abstract

   This document specifies a set of methods, headers, properties and
   content-types composing WebDAV SEARCH, an application of the HTTP/1.1
   protocol to efficiently search for DAV resources based upon a set of
   client-supplied criteria.






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Editorial Note (To be removed by RFC Editor before publication)

   Please send comments to the Distributed Authoring and Versioning
   (WebDAV) DASL mailing list at <mailto:www-webdav-dasl@w3.org>, which
   may be joined by sending a message with subject "subscribe" to
   <mailto:www-webdav-dasl-request@w3.org>.  Discussions of the WebDAV
   DASL mailing list are archived at
   <http://lists.w3.org/Archives/Public/www-webdav-dasl/>.

   An issues list and XML and HTML versions of this draft are available
   from <http://greenbytes.de/tech/webdav/#draft-reschke-webdav-search>.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  6
     1.1.  DASL . . . . . . . . . . . . . . . . . . . . . . . . . . .  6
     1.2.  Relationship to DAV  . . . . . . . . . . . . . . . . . . .  6
     1.3.  Terms  . . . . . . . . . . . . . . . . . . . . . . . . . .  6
     1.4.  Notational Conventions . . . . . . . . . . . . . . . . . .  8
     1.5.  Note on Usage of 'DAV:' XML Namespace  . . . . . . . . . .  9
     1.6.  An Overview of DASL at Work  . . . . . . . . . . . . . . .  9
   2.  The SEARCH Method  . . . . . . . . . . . . . . . . . . . . . .  9
     2.1.  Overview . . . . . . . . . . . . . . . . . . . . . . . . .  9
     2.2.  The Request  . . . . . . . . . . . . . . . . . . . . . . .  9
       2.2.1.  The Request-URI  . . . . . . . . . . . . . . . . . . . 10
       2.2.2.  The Request Body . . . . . . . . . . . . . . . . . . . 10
     2.3.  The Successful 207 (Multistatus) Response  . . . . . . . . 11
       2.3.1.  Result Set Truncation  . . . . . . . . . . . . . . . . 11
       2.3.2.  Extending the PROPFIND Response  . . . . . . . . . . . 12
       2.3.3.  Example: A Simple Request and Response . . . . . . . . 12
       2.3.4.  Example: Result Set Truncation . . . . . . . . . . . . 13
     2.4.  Unsuccessful Responses . . . . . . . . . . . . . . . . . . 14
       2.4.1.  Example of an Invalid Scope  . . . . . . . . . . . . . 14
   3.  Discovery of Supported Query Grammars  . . . . . . . . . . . . 15
     3.1.  The OPTIONS Method . . . . . . . . . . . . . . . . . . . . 15
     3.2.  The DASL Response Header . . . . . . . . . . . . . . . . . 16
     3.3.  DAV:supported-query-grammar-set (protected)  . . . . . . . 16
     3.4.  Example: Grammar Discovery . . . . . . . . . . . . . . . . 16
   4.  Query Schema Discovery: QSD  . . . . . . . . . . . . . . . . . 19
     4.1.  Additional SEARCH Semantics  . . . . . . . . . . . . . . . 19
       4.1.1.  Example of Query Schema Discovery  . . . . . . . . . . 20
   5.  The DAV:basicsearch Grammar  . . . . . . . . . . . . . . . . . 21
     5.1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . 21
     5.2.  The DAV:basicsearch DTD  . . . . . . . . . . . . . . . . . 22
       5.2.1.  Example Query  . . . . . . . . . . . . . . . . . . . . 24
     5.3.  DAV:select . . . . . . . . . . . . . . . . . . . . . . . . 25
     5.4.  DAV:from . . . . . . . . . . . . . . . . . . . . . . . . . 25



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       5.4.1.  Relationship to the Request-URI  . . . . . . . . . . . 25
       5.4.2.  Scope  . . . . . . . . . . . . . . . . . . . . . . . . 26
     5.5.  DAV:where  . . . . . . . . . . . . . . . . . . . . . . . . 26
       5.5.1.  Use of Three-Valued Logic in Queries . . . . . . . . . 26
       5.5.2.  Handling Optional Operators  . . . . . . . . . . . . . 26
       5.5.3.  Treatment of NULL Values . . . . . . . . . . . . . . . 26
       5.5.4.  Treatment of Properties with mixed/element Content . . 27
       5.5.5.  Example: Testing for Equality  . . . . . . . . . . . . 27
       5.5.6.  Example: Relative Comparisons  . . . . . . . . . . . . 27
     5.6.  DAV:orderby  . . . . . . . . . . . . . . . . . . . . . . . 28
       5.6.1.  Example of Sorting . . . . . . . . . . . . . . . . . . 28
     5.7.  Boolean Operators: DAV:and, DAV:or, and DAV:not  . . . . . 28
     5.8.  DAV:eq . . . . . . . . . . . . . . . . . . . . . . . . . . 29
     5.9.  DAV:lt, DAV:lte, DAV:gt, DAV:gte . . . . . . . . . . . . . 29
     5.10. DAV:literal  . . . . . . . . . . . . . . . . . . . . . . . 29
     5.11. DAV:typed-literal (optional) . . . . . . . . . . . . . . . 29
       5.11.1. Example for Typed Numerical Comparison . . . . . . . . 30
     5.12. Support for Matching xml:lang Attributes on Properties . . 30
       5.12.1. DAV:language-defined (optional)  . . . . . . . . . . . 31
       5.12.2. DAV:language-matches (optional)  . . . . . . . . . . . 31
       5.12.3. Example of Language-Aware Matching . . . . . . . . . . 31
     5.13. DAV:is-collection  . . . . . . . . . . . . . . . . . . . . 31
       5.13.1. Example of DAV:is-collection . . . . . . . . . . . . . 32
     5.14. DAV:is-defined . . . . . . . . . . . . . . . . . . . . . . 32
     5.15. DAV:like . . . . . . . . . . . . . . . . . . . . . . . . . 32
       5.15.1. Syntax for the Literal Pattern . . . . . . . . . . . . 33
       5.15.2. Example of DAV:like  . . . . . . . . . . . . . . . . . 33
     5.16. DAV:contains . . . . . . . . . . . . . . . . . . . . . . . 33
       5.16.1. Result Scoring (DAV:score Element) . . . . . . . . . . 34
       5.16.2. Ordering by Score  . . . . . . . . . . . . . . . . . . 35
       5.16.3. Examples . . . . . . . . . . . . . . . . . . . . . . . 35
     5.17. Limiting the Result Set  . . . . . . . . . . . . . . . . . 35
       5.17.1. Relationship to Result Ordering  . . . . . . . . . . . 35
     5.18. The 'caseless' XML Attribute . . . . . . . . . . . . . . . 36
     5.19. Query Schema for DAV:basicsearch . . . . . . . . . . . . . 36
       5.19.1. DTD for DAV:basicsearch QSD  . . . . . . . . . . . . . 36
       5.19.2. DAV:propdesc Element . . . . . . . . . . . . . . . . . 37
       5.19.3. The DAV:datatype Property Description  . . . . . . . . 37
       5.19.4. The DAV:searchable Property Description  . . . . . . . 38
       5.19.5. The DAV:selectable Property Description  . . . . . . . 38
       5.19.6. The DAV:sortable Property Description  . . . . . . . . 38
       5.19.7. The DAV:caseless Property Description  . . . . . . . . 38
       5.19.8. The DAV:operators XML Element  . . . . . . . . . . . . 38
       5.19.9. Example of Query Schema for DAV:basicsearch  . . . . . 40
   6.  Internationalization Considerations  . . . . . . . . . . . . . 40
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . . 41
     7.1.  Implications of XML External Entities  . . . . . . . . . . 41
   8.  Scalability  . . . . . . . . . . . . . . . . . . . . . . . . . 42



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   9.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 42
     9.1.  HTTP Headers . . . . . . . . . . . . . . . . . . . . . . . 42
       9.1.1.  DASL . . . . . . . . . . . . . . . . . . . . . . . . . 42
   10. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 42
   11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 43
   12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 43
     12.1. Normative References . . . . . . . . . . . . . . . . . . . 43
     12.2. Informative References . . . . . . . . . . . . . . . . . . 44
   Appendix A.  Three-Valued Logic in DAV:basicsearch . . . . . . . . 45
   Appendix B.  Candidates for Future Protocol Extensions . . . . . . 46
     B.1.  Collation Support  . . . . . . . . . . . . . . . . . . . . 46
     B.2.  Count  . . . . . . . . . . . . . . . . . . . . . . . . . . 47
     B.3.  Diagnostics for Unsupported Queries  . . . . . . . . . . . 47
     B.4.  Language Matching  . . . . . . . . . . . . . . . . . . . . 47
     B.5.  Matching Media Types . . . . . . . . . . . . . . . . . . . 47
     B.6.  Query by Name  . . . . . . . . . . . . . . . . . . . . . . 48
     B.7.  Result Paging  . . . . . . . . . . . . . . . . . . . . . . 48
     B.8.  Search Scope Discovery . . . . . . . . . . . . . . . . . . 48
   Appendix C.  Change Log (to be removed by RFC Editor before
                publication)  . . . . . . . . . . . . . . . . . . . . 48
     C.1.  From draft-davis-dasl-protocol-xxx . . . . . . . . . . . . 48
     C.2.  since start of draft-reschke-webdav-search . . . . . . . . 50
     C.3.  since draft-reschke-webdav-search-00 . . . . . . . . . . . 52
     C.4.  since draft-reschke-webdav-search-01 . . . . . . . . . . . 52
     C.5.  since draft-reschke-webdav-search-02 . . . . . . . . . . . 52
     C.6.  since draft-reschke-webdav-search-03 . . . . . . . . . . . 53
     C.7.  since draft-reschke-webdav-search-04 . . . . . . . . . . . 53
     C.8.  since draft-reschke-webdav-search-05 . . . . . . . . . . . 54
     C.9.  since draft-reschke-webdav-search-06 . . . . . . . . . . . 54
     C.10. since draft-reschke-webdav-search-07 . . . . . . . . . . . 55
     C.11. since draft-reschke-webdav-search-08 . . . . . . . . . . . 55
     C.12. since draft-reschke-webdav-search-09 . . . . . . . . . . . 55
     C.13. since draft-reschke-webdav-search-10 . . . . . . . . . . . 56
     C.14. since draft-reschke-webdav-search-11 . . . . . . . . . . . 56
     C.15. since draft-reschke-webdav-search-12 . . . . . . . . . . . 56
     C.16. since draft-reschke-webdav-search-13 . . . . . . . . . . . 56
     C.17. since draft-reschke-webdav-search-14 . . . . . . . . . . . 56
     C.18. since draft-reschke-webdav-search-15 . . . . . . . . . . . 57
   Appendix D.  Resolved issues (to be removed by RFC Editor
                before publication) . . . . . . . . . . . . . . . . . 57
     D.1.  standardstrack . . . . . . . . . . . . . . . . . . . . . . 57
     D.2.  acls . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
     D.3.  scope-discovery  . . . . . . . . . . . . . . . . . . . . . 58
     D.4.  3.2-listsyntax . . . . . . . . . . . . . . . . . . . . . . 58
   Appendix E.  Open issues (to be removed by RFC Editor prior to
                publication)  . . . . . . . . . . . . . . . . . . . . 58
     E.1.  edit . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
   Index  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58



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   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 60
   Intellectual Property and Copyright Statements . . . . . . . . . . 62

















































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1.  Introduction

1.1.  DASL

   This document defines Web Distributed Authoring and Versioning
   (WebDAV) SEARCH, an application of HTTP/1.1 forming a lightweight
   search protocol to transport queries and result sets that allows
   clients to make use of server-side search facilities.  It is based on
   the expired internet draft for DAV Searching & Locating [DASL].
   [DASLREQ] describes the motivation for DASL.  In this specification,
   the terms "WebDAV SEARCH" and "DASL" are used interchangeably.

   DASL minimizes the complexity of clients so as to facilitate
   widespread deployment of applications capable of utilizing the DASL
   search mechanisms.

   DASL consists of:

   o  the SEARCH method and the request/response formats defined for it
      (Section 2),

   o  feature discovery through the "DASL" response header and the
      optional DAV:supported-grammar-set property (Section 3),

   o  optional grammar schema discovery (Section 4) and

   o  one mandatory grammar: DAV:basicsearch (Section 5).

1.2.  Relationship to DAV

   DASL relies on the resource and property model defined by [RFC4918].
   DASL does not alter this model.  Instead, DASL allows clients to
   access DAV-modeled resources through server-side search.

1.3.  Terms

   This document uses the terms defined in [RFC2616], in [RFC4918], in
   [RFC3253] and in this section.

   Criteria

      An expression against which each resource in the search scope is
      evaluated.

   Query

      A query is a combination of a search scope, search criteria,
      result record definition, sort specification, and a search



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      modifier.

   Query Grammar

      A set of definitions of XML elements, attributes, and constraints
      on their relations and values that defines a set of queries and
      the intended semantics.

   Query Schema

      A listing, for any given grammar and scope, of the properties and
      operators that may be used in a query with that grammar and scope.

   Result

      A result is a result set, optionally augmented with other
      information describing the search as a whole.

   Result Record

      A description of a resource.  A result record is a set of
      properties, and possibly other descriptive information.

   Result Record Definition

      A specification of the set of properties to be returned in the
      result record.

   Result Set

      A set of records, one for each resource for which the search
      criteria evaluated to True.

   Scope

      A set of resources to be searched.

   Search Arbiter

      A resource that supports the SEARCH method.

   Search Modifier

      An instruction that governs the execution of the query but is not
      part of the search scope, result record definition, the search
      criteria, or the sort specification.  An example of a search
      modifier is one that controls how much time the server can spend
      on the query before giving a response.



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   Sort Specification

      A specification of an ordering on the result records in the result
      set.

1.4.  Notational Conventions

   This specification uses the Augmented Backus-Naur Form (ABNF)
   notation of [RFC5234], unless explicitly stated otherwise.

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

   This document uses XML DTD fragments ([XML], Section 3.2) as a purely
   notational convention.  WebDAV request and response bodies can not be
   validated by a DTD due to the specific extensibility rules defined in
   Section 17 of [RFC4918] and due to the fact that all XML elements
   defined by this specification use the XML namespace name "DAV:".  In
   particular:

   1.  element names use the "DAV:" namespace,

   2.  element ordering is irrelevant unless explicitly stated,

   3.  extension elements (elements not already defined as valid child
       elements) may be added anywhere, except when explicitly stated
       otherwise,

   4.  extension attributes (attributes not already defined as valid for
       this element) may be added anywhere, except when explicitly
       stated otherwise.

   When an XML element type in the "DAV:" namespace is referenced in
   this document outside of the context of an XML fragment, the string
   "DAV:" will be prefixed to the element type.

   Similarly, when an XML element type in the namespace
   "http://www.w3.org/2001/XMLSchema" is referenced in this document
   outside of the context of an XML fragment, the string "xs:" will be
   prefixed to the element type.

   This document inherits, and sometimes extends, DTD productions from
   Section 14 of [RFC4918].







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1.5.  Note on Usage of 'DAV:' XML Namespace

   This specification defines elements, properties and condition names
   in the XML namespace "DAV:".  In general, only specifications
   authored by IETF working groups are supposed to do this.  In this
   case an exception was made, because WebDAV SEARCH started its life in
   the IETF DASL working group (<http://www.webdav.org/dasl/>, and at
   the time the working group closed down there was already significant
   deployment of this specification.

1.6.  An Overview of DASL at Work

   One can express the basic usage of DASL in the following steps:

   o  The client constructs a query using the DAV:basicsearch grammar.

   o  The client invokes the SEARCH method on a resource that will
      perform the search (the search arbiter) and includes a text/xml or
      application/xml request entity that contains the query.

   o  The search arbiter performs the query.

   o  The search arbiter sends the results of the query back to the
      client in the response.  The server MUST send an entity that
      matches the WebDAV multistatus format ([RFC4918], Section 13).


2.  The SEARCH Method

2.1.  Overview

   The client invokes the SEARCH method to initiate a server-side
   search.  The body of the request defines the query.  The server MUST
   emit an entity matching the WebDAV multistatus format ([RFC4918],
   Section 13).

   The SEARCH method plays the role of transport mechanism for the query
   and the result set.  It does not define the semantics of the query.
   The type of the query defines the semantics.

2.2.  The Request

   The client invokes the SEARCH method on the resource named by the
   Request-URI.







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2.2.1.  The Request-URI

   The Request-URI identifies the search arbiter.  Any HTTP resource may
   function as search arbiter.  It is not a new type of resource (in the
   sense of DAV:resourcetype as defined in [RFC4918], Section 15.9), nor
   does it have to be a WebDAV-compliant resource.

   The SEARCH method defines no relationship between the arbiter and the
   scope of the search, rather the particular query grammar used in the
   query defines the relationship.  For example, a query grammar may
   force the Request-URI to correspond exactly to the search scope.

2.2.2.  The Request Body

   The server MUST process a text/xml or application/xml request body,
   and MAY process request bodies in other formats.  See [RFC3023] for
   guidance on packaging XML in requests.

   Marshalling:

      If a request body with content type text/xml or application/xml is
      included, it MUST be either a DAV:searchrequest or a DAV:query-
      schema-discovery XML element.  Its single child element identifies
      the query grammar.

      For DAV:searchrequest, the definition of search criteria, the
      result record, and any other details needed to perform the search
      depend on the individual search grammar.

      For DAV:query-schema-discovery, the semantics is defined in
      Section 4.

   Preconditions:

      (DAV:search-grammar-discovery-supported): when an XML request body
      is present and has a DAV:query-schema-discovery document element,
      the server MUST support the query schema discovery mechanism
      described in Section 4.

      (DAV:search-grammar-supported): when an XML request body is
      present, the search grammar identified by the document element's
      child element must be a supported search grammar.

      (DAV:search-multiple-scope-supported): if the SEARCH request
      specified multiple scopes, the server MUST support this optional
      feature.





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      (DAV:search-scope-valid): the supplied search scope must be valid.
      There can be various reasons for a search scope to be invalid,
      including unsupported URI schemes and communication problems.
      Servers MAY add [RFC4918] compliant DAV:response elements as
      content to the condition element indicating the precise reason for
      the failure.

2.3.  The Successful 207 (Multistatus) Response

   If the server returns 207 (Multistatus), then the search proceeded
   successfully and the response MUST use the WebDAV multistatus format
   ([RFC4918], Section 13).  The results of this method SHOULD NOT be
   cached.

   There MUST be one DAV:response for each resource that matched the
   search criteria.  For each such response, the DAV:href element
   contains the URI of the resource, and the response MUST include a
   DAV:propstat element.

      Note: the WebDAV multistatus format requires at least one DAV:
      response child element.  This specification relaxes that
      restriction so that empty results can be represented.

   Note that for each matching resource found there may be multiple URIs
   within the search scope mapped to it.  In this case, a server SHOULD
   report only one of these URIs.  Clients can use the live property
   DAV:resource-id defined in Section 3.1 of [draft-ietf-webdav-bind] to
   identify possible duplicates.

2.3.1.  Result Set Truncation

   A server MAY limit the number of resources in a reply, for example to
   limit the amount of resources expended in processing a query.  If it
   does so, the reply MUST use status code 207, return a DAV:multistatus
   response body and indicate a status of 507 (Insufficient Storage) for
   the search arbiter URI.  It SHOULD include the partial results.

   When a result set is truncated, there may be many more resources that
   satisfy the search criteria but that were not examined.

   If partial results are included and the client requested an ordered
   result set in the original request, then any partial results that are
   returned MUST be ordered as the client directed.

   Note that the partial results returned MAY be any subset of the
   result set that would have satisfied the original query.





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2.3.2.  Extending the PROPFIND Response

   A response MAY include more information than PROPFIND defines so long
   as the extra information does not invalidate the PROPFIND response.
   Query grammars SHOULD define how the response matches the PROPFIND
   response.

2.3.3.  Example: A Simple Request and Response

   This example demonstrates the request and response framework.  The
   following XML document shows a simple (hypothetical) natural language
   query.  The name of the query element is natural-language-query in
   the XML namespace "http://example.com/foo".  The actual query is
   "Find the locations of good Thai restaurants in Los Angeles".  For
   this hypothetical query, the arbiter returns two properties for each
   selected resource.

   >> Request:

   SEARCH / HTTP/1.1
   Host: example.org
   Content-Type: application/xml; charset="utf-8"
   Content-Length: 252

   <?xml version="1.0" encoding="UTF-8"?>
   <D:searchrequest xmlns:D="DAV:" xmlns:F="http://example.com/foo">
     <F:natural-language-query>
       Find the locations of good Thai restaurants in Los Angeles
     </F:natural-language-query>
   </D:searchrequest>





















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   >> Response:

   HTTP/1.1 207 Multi-Status
   Content-Type: text/xml; charset="utf-8"
   Content-Length: 429

   <?xml version="1.0" encoding="UTF-8"?>
   <D:multistatus xmlns:D="DAV:"
      xmlns:R="http://example.org/propschema">
     <D:response>
       <D:href>http://siamiam.example/</D:href>
       <D:propstat>
         <D:prop>
           <R:location>259 W. Hollywood</R:location>
           <R:rating><R:stars>4</R:stars></R:rating>
         </D:prop>
         <D:status>HTTP/1.1 200 OK</D:status>
       </D:propstat>
     </D:response>
   </D:multistatus>

2.3.4.  Example: Result Set Truncation

   In the example below, the server returns just two results, and then
   indicates that the result is truncated by adding a DAV:response
   element for the search arbiter resource with 507 (Insufficient
   Storage) status.

   >> Request:

   SEARCH / HTTP/1.1
   Host: example.net
   Content-Type: text/xml; charset="utf-8"
   Content-Length: xxx

    ... the query goes here ...















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   >> Response:

   HTTP/1.1 207 Multistatus
   Content-Type: text/xml; charset="utf-8"
   Content-Length: 640

   <?xml version="1.0" encoding="utf-8"?>
   <D:multistatus xmlns:D="DAV:">
     <D:response>
       <D:href>http://www.example.net/sounds/unbrokenchain.au</D:href>
       <D:status>HTTP/1.1 200 OK</D:status>
     </D:response>
     <D:response>
       <D:href>http://tech.mit.example/arch96/photos/Lesh1.jpg</D:href>
       <D:status>HTTP/1.1 200 OK</D:status>
     </D:response>
     <D:response>
       <D:href>http://example.net</D:href>
       <D:status>HTTP/1.1 507 Insufficient Storage</D:status>
       <D:responsedescription xml:lang="en">
          Only first two matching records were returned
       </D:responsedescription>
     </D:response>
   </D:multistatus>

2.4.  Unsuccessful Responses

   If a SEARCH request could not be executed or the attempt to execute
   it resulted in an error, the server MUST indicate the failure with an
   appropriate status code and SHOULD add a response body as defined in
   [RFC3253], Section 1.6.  Unless otherwise stated, condition elements
   are empty, however specific condition elements MAY include additional
   child elements that describe the error condition in more detail.

2.4.1.  Example of an Invalid Scope

   In the example below, a request failed because the scope identifies a
   HTTP resource that was not found.













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   >> Response:

   HTTP/1.1 409 Conflict
   Content-Type: text/xml; charset="utf-8"
   Content-Length: 275

   <?xml version="1.0" encoding="UTF-8"?>
   <d:error xmlns:d="DAV:">
     <d:search-scope-valid>
       <d:response>
         <d:href>http://www.example.com/X</d:href>
         <d:status>HTTP/1.1 404 Object Not Found</d:status>
       </d:response>
     </d:search-scope-valid>
   </d:error>


3.  Discovery of Supported Query Grammars

   Servers MUST support discovery of the query grammars supported by a
   search arbiter resource.

   Clients can determine which query grammars are supported by an
   arbiter by invoking OPTIONS on the search arbiter.  If the resource
   supports SEARCH, then the DASL response header will appear in the
   response.  The DASL response header lists the supported grammars.

   Servers supporting the WebDAV extensions [RFC3253] and/or [RFC3744]
   MUST also

   o  report SEARCH in the live property DAV:supported-method-set for
      all search arbiter resources and

   o  support the live property DAV:supported-query-grammar-set as
      defined in Section 3.3.

3.1.  The OPTIONS Method

   The OPTIONS method allows the client to discover if a resource
   supports the SEARCH method and to determine the list of search
   grammars supported for that resource.

   The client issues the OPTIONS method against a resource named by the
   Request-URI.  This is a normal invocation of OPTIONS as defined in
   Section 9.2 of [RFC2616].

   If a resource supports the SEARCH method, then the server MUST list
   SEARCH in the Allow header defined in Section 14.7 of [RFC2616].



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   DASL servers MUST include the DASL header in the OPTIONS response.
   This header identifies the search grammars supported by that
   resource.

3.2.  The DASL Response Header

   DASLHeader = "DASL" ":" 1#Coded-URL
   Coded-URL  = <defined in Section 10.1 of [RFC4918]>

   (This grammar uses the augmented BNF format defined in Section 2.1 of
   [RFC2616])

   The DASL response header indicates server support for query grammars
   in the OPTIONS method.  The value is a list of URIs that indicate the
   types of supported grammars.  Note that although the URIs can be used
   to identify each supported search grammar, there is not necessarily a
   direct relationship between the URI and the XML element name that can
   be used in XML based SEARCH requests (the element name itself is
   identified by its namespace name (a URI reference) and the element's
   local name).

      Note: this header field value is defined as a comma-separated list
      ([RFC2616], Section 4.2), thus grammar URIs can appear in multiple
      header instances, separated by commas, or both.

   For example:

   DASL: <http://foobar.example/syntax1>,
         <http://akuma.example/syntax2>, <DAV:basicsearch>
   DASL: <http://example.com/foo/natural-language-query>

3.3.  DAV:supported-query-grammar-set (protected)

   This WebDAV property is required for any server supporting either
   [RFC3253] and/or [RFC3744] and identifies the XML based query
   grammars that are supported by the search arbiter resource.

   <!ELEMENT supported-query-grammar-set (supported-query-grammar*)>
   <!ELEMENT supported-query-grammar (grammar)>
   <!ELEMENT grammar ANY>
   <!-- ANY value: a query grammar element type -->

3.4.  Example: Grammar Discovery

   This example shows that the server supports search on the /somefolder
   resource with the query grammars: DAV:basicsearch,
   http://foobar.example/syntax1 and http://akuma.example/syntax2.  Note
   that servers supporting WebDAV SEARCH MUST support DAV:basicsearch.



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   >> Request:

   OPTIONS /somefolder HTTP/1.1
   Host: example.org

   >> Response:

   HTTP/1.1 200 OK
   Allow: OPTIONS, GET, HEAD, POST, PUT, DELETE, TRACE, COPY, MOVE
   Allow: MKCOL, PROPFIND, PROPPATCH, LOCK, UNLOCK, SEARCH
   DASL: <DAV:basicsearch>
   DASL: <http://foobar.example/syntax1>, <http://akuma.example/syntax2>

   This example shows the equivalent taking advantage of a server's
   support for DAV:supported-method-set and DAV:supported-query-grammar-
   set.

   >> Request:

   PROPFIND /somefolder HTTP/1.1
   Host: example.org
   Depth: 0
   Content-Type: text/xml; charset="utf-8"
   Content-Length: 165

   <?xml version="1.0" encoding="UTF-8" ?>
   <propfind xmlns="DAV:">
     <prop>
       <supported-query-grammar-set/>
       <supported-method-set/>
     </prop>
   </propfind>



















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   >> Response:

   HTTP/1.1 207 Multi-Status
   Content-Type: text/xml; charset="utf-8"
   Content-Length: 1349

   <?xml version="1.0" encoding="utf-8" ?>
   <multistatus xmlns="DAV:">
    <response>
     <href>http://example.org/somefolder</href>
     <propstat>
      <prop>
       <supported-query-grammar-set>
        <supported-query-grammar>
         <grammar><basicsearch/></grammar>
        </supported-query-grammar>
        <supported-query-grammar>
         <grammar><syntax1 xmlns="http://foobar.example/"/></grammar>
        </supported-query-grammar>
        <supported-query-grammar>
         <grammar><syntax2 xmlns="http://akuma.example/"/></grammar>
        </supported-query-grammar>
       </supported-query-grammar-set>
       <supported-method-set>
        <supported-method name="COPY" />
        <supported-method name="DELETE" />
        <supported-method name="GET" />
        <supported-method name="HEAD" />
        <supported-method name="LOCK" />
        <supported-method name="MKCOL" />
        <supported-method name="MOVE" />
        <supported-method name="OPTIONS" />
        <supported-method name="POST" />
        <supported-method name="PROPFIND" />
        <supported-method name="PROPPATCH" />
        <supported-method name="PUT" />
        <supported-method name="SEARCH" />
        <supported-method name="TRACE" />
        <supported-method name="UNLOCK" />
       </supported-method-set>
      </prop>
      <status>HTTP/1.1 200 OK</status>
     </propstat>
    </response>
   </multistatus>

   Note that the query grammar element names marshalled as part of the
   DAV:supported-query-grammar-set can be directly used as element names



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   in an XML based query.


4.  Query Schema Discovery: QSD

   Servers MAY support the discovery of the schema for a query grammar.

   The DASL response header and the DAV:supported-query-grammar-set
   property provide means for clients to discover the set of query
   grammars supported by a resource.  This alone is not sufficient
   information for a client to generate a query.  For example, the DAV:
   basicsearch grammar defines a set of queries consisting of a set of
   operators applied to a set of properties and values, but the grammar
   itself does not specify which properties may be used in the query.
   QSD for the DAV:basicsearch grammar allows a client to discover the
   set of properties that are searchable, selectable, and sortable.
   Moreover, although the DAV:basicsearch grammar defines a minimal set
   of operators, it is possible that a resource might support additional
   operators in a query.  For example, a resource might support an
   optional operator that can be used to express content-based queries
   in a proprietary syntax.  QSD allows a client to discover these
   operators and their syntax.  The set of discoverable quantities will
   differ from grammar to grammar, but each grammar can define a means
   for a client to discover what can be discovered.

   In general, the schema for a given query grammar depends on both the
   resource (the arbiter) and the scope.  A given resource might have
   access to one set of properties for one potential scope, and another
   set for a different scope.  For example, consider a server able to
   search two distinct collections, one holding cooking recipes, the
   other design documents for nuclear weapons.  While both collections
   might support properties such as author, title, and date, the first
   might also define properties such as calories and preparation time,
   while the second defined properties such as yield and applicable
   patents.  Two distinct arbiters indexing the same collection might
   also have access to different properties.  For example, the recipe
   collection mentioned above might also be indexed by a value-added
   server that also stored the names of chefs who had tested the recipe.
   Note also that the available query schema might also depend on other
   factors, such as the identity of the principal conducting the search,
   but these factors are not exposed in this protocol.

4.1.  Additional SEARCH Semantics

   Each query grammar supported by DASL defines its own syntax for
   expressing the possible query schema.  A client retrieves the schema
   for a given query grammar on an arbiter resource with a given scope
   by invoking the SEARCH method on that arbiter with that grammar and



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   scope and with a root element of DAV:query-schema-discovery rather
   than DAV:searchrequest.

   Marshalling:

      The request body MUST be a DAV:query-schema-discovery element.

   <!ELEMENT query-schema-discovery ANY>
   <!-- ANY value: XML element specifying the query grammar
                   and the scope -->

      The response body takes the form of a DAV:multistatus element
      ([RFC4918], Section 13), where DAV:response is extended to hold
      the returned query grammar inside a DAV:query-schema container
      element.

   <!ELEMENT response (href, status, query-schema?,
     responsedescription? >
   <!ELEMENT query-schema ANY>

   The content of this container is an XML element whose name and syntax
   depend upon the grammar, and whose value may (and likely will) vary
   depending upon the grammar, arbiter, and scope.

4.1.1.  Example of Query Schema Discovery

   In this example, the arbiter is recipes.example, the grammar is DAV:
   basicsearch, the scope is also recipes.example.

   >> Request:

   SEARCH / HTTP/1.1
   Host: recipes.example
   Content-Type: application/xml; charset="utf-8"
   Content-Length: 258

   <?xml version="1.0"?>
   <query-schema-discovery xmlns="DAV:">
     <basicsearch>
       <from>
         <scope>
           <href>http://recipes.example</href>
           <depth>infinity</depth>
         </scope>
       </from>
     </basicsearch>
   </query-schema-discovery>




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   >> Response:

   HTTP/1.1 207 Multistatus
   Content-Type: application/xml; charset="utf-8"
   Content-Length: xxx

   <?xml version="1.0"?>
   <multistatus xmlns="DAV:">
     <response>
       <href>http://recipes.example</href>
       <status>HTTP/1.1 200 OK</status>
       <query-schema>
         <basicsearchschema>
           <!-- (See Section 5.19 for
           the actual contents) -->
         </basicsearchschema>
       </query-schema>
     </response>
   </multistatus>

   The query schema for DAV:basicsearch is defined in Section 5.19.


5.  The DAV:basicsearch Grammar

5.1.  Introduction

   DAV:basicsearch uses an extensible XML syntax that allows clients to
   express search requests that are generally useful for WebDAV
   scenarios.  DASL-extended servers MUST accept this grammar, and MAY
   accept other grammars.

   DAV:basicsearch has several components:

   o  DAV:select provides the result record definition.

   o  DAV:from defines the scope.

   o  DAV:where defines the criteria.

   o  DAV:orderby defines the sort order of the result set.

   o  DAV:limit provides constraints on the query as a whole.








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5.2.  The DAV:basicsearch DTD

   <!-- "basicsearch" element -->

   <!ELEMENT basicsearch   (select, from, where?, orderby?, limit?) >

   <!-- "select" element -->

   <!ELEMENT select        (allprop | prop) >

   <!-- "from" element -->

   <!ELEMENT from          (scope+) >
   <!ELEMENT scope         (href, depth, include-versions?) >
   <!ELEMENT include-versions EMPTY >

   <!-- "where" element -->


































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   <!ENTITY % comp_ops     "eq | lt | gt| lte | gte">
   <!ENTITY % log_ops      "and | or | not">
   <!ENTITY % special_ops  "is-collection | is-defined |
                            language-defined | language-matches">
   <!ENTITY % string_ops   "like">
   <!ENTITY % content_ops  "contains">

   <!ENTITY % all_ops      "%comp_ops; | %log_ops; | %special_ops; |
                            %string_ops; | %content_ops;">

   <!ELEMENT where         ( %all_ops; ) >

   <!ELEMENT and           ( %all_ops; )+ >

   <!ELEMENT or            ( %all_ops; )+ >

   <!ELEMENT not           ( %all_ops; ) >

   <!ELEMENT lt            (prop, (literal|typed-literal)) >
   <!ATTLIST lt            caseless   (yes|no) #IMPLIED>

   <!ELEMENT lte           (prop, (literal|typed-literal)) >
   <!ATTLIST lte           caseless   (yes|no) #IMPLIED>

   <!ELEMENT gt            (prop, (literal|typed-literal)) >
   <!ATTLIST gt            caseless   (yes|no) #IMPLIED>

   <!ELEMENT gte           (prop, (literal|typed-literal)) >
   <!ATTLIST gte           caseless   (yes|no) #IMPLIED>

   <!ELEMENT eq            (prop, (literal|typed-literal)) >
   <!ATTLIST eq            caseless   (yes|no) #IMPLIED>

   <!ELEMENT literal       (#PCDATA)>
   <!ELEMENT typed-literal (#PCDATA)>
   <!ATTLIST typed-literal xsi:type CDATA #IMPLIED>

   <!ELEMENT is-collection EMPTY >
   <!ELEMENT is-defined    (prop) >

   <!ELEMENT language-defined    (prop) >
   <!ELEMENT language-matches    (prop, literal) >

   <!ELEMENT like          (prop, literal) >
   <!ATTLIST like          caseless   (yes|no) #IMPLIED>

   <!ELEMENT contains      (#PCDATA)>




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   <!-- "orderby" element -->

   <!ELEMENT orderby       (order+) >
   <!ELEMENT order         ((prop | score), (ascending | descending)?)>
   <!ATTLIST order         caseless   (yes|no) #IMPLIED>
   <!ELEMENT ascending     EMPTY>
   <!ELEMENT descending    EMPTY>

   <!-- "limit" element -->

   <!ELEMENT limit         (nresults) >
   <!ELEMENT nresults      (#PCDATA) >

5.2.1.  Example Query

   This query retrieves the content length values for all resources
   located under the server's "/container1/" URI namespace whose length
   exceeds 10000 sorted ascending by size.

   <d:searchrequest xmlns:d="DAV:">
     <d:basicsearch>
       <d:select>
         <d:prop><d:getcontentlength/></d:prop>
       </d:select>
       <d:from>
         <d:scope>
           <d:href>/container1/</d:href>
           <d:depth>infinity</d:depth>
         </d:scope>
       </d:from>
       <d:where>
         <d:gt>
           <d:prop><d:getcontentlength/></d:prop>
           <d:literal>10000</d:literal>
         </d:gt>
       </d:where>
       <d:orderby>
         <d:order>
           <d:prop><d:getcontentlength/></d:prop>
           <d:ascending/>
         </d:order>
       </d:orderby>
     </d:basicsearch>
   </d:searchrequest>







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5.3.  DAV:select

   DAV:select defines the result record, which is a set of properties
   and values.  This document defines two possible values: DAV:allprop
   and DAV:prop, both defined in Section 14 of [RFC4918].

5.4.  DAV:from

   <!ELEMENT scope            (href, depth, include-versions?) >
   <!ELEMENT include-versions EMPTY >

   DAV:from defines the query scope.  This contains one or more DAV:
   scope elements.  Support for multiple scope elements is optional,
   however servers MUST fail a request specifying multiple DAV:scope
   elements if they can't support it (see Section 2.2.2, precondition
   DAV:search-multiple-scope-supported).  The scope element contains
   mandatory DAV:href and DAV:depth elements.

   DAV:href indicates the URI reference ([RFC3986], Section 4.1) to use
   as a scope.

   When the scope is a collection, if DAV:depth is "0", the search
   includes only the collection.  When it is "1", the search includes
   the collection and its immediate children.  When it is "infinity", it
   includes the collection and all its progeny.

   When the scope is not a collection, the depth is ignored and the
   search applies just to the resource itself.

   If the server supports WebDAV Redirect Reference Resources
   ([RFC4437]) and the search scope contains a redirect reference
   resource, then it applies only to that resource, not to its target.

   When the child element DAV:include-versions is present, the search
   scope will include all versions (see [RFC3253], Section 2.2.1) of all
   version-controlled resources in scope.  Servers that do support
   versioning but do not support the DAV:include-versions feature MUST
   signal an error if it is used in a query (see Section 2.2.2,
   precondition DAV:search-scope-valid).

5.4.1.  Relationship to the Request-URI

   If the DAV:scope element is an URI ([RFC3986], Section 3), the scope
   is exactly that URI.

   If the DAV:scope element is a relative reference ([RFC3986], Section
   4.2), the scope is taken to be relative to the Request-URI.




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5.4.2.  Scope

   A Scope can be an arbitrary URI reference.

   Servers, of course, may support only particular scopes.  This may
   include limitations for particular schemes such as "http:" or "ftp:"
   or certain URI namespaces.  However, WebDAV compliant search arbiters
   minimally SHOULD support scopes that match their own URI.

5.5.  DAV:where

   The DAV:where element defines the search condition for inclusion of
   resources in the result set.  The value of this element is an XML
   element that defines a search operator that evaluates to one of the
   Boolean truth values TRUE, FALSE, or UNKNOWN.  The search operator
   contained by DAV:where may itself contain and evaluate additional
   search operators as operands, which in turn may contain and evaluate
   additional search operators as operands, etc. recursively.

5.5.1.  Use of Three-Valued Logic in Queries

   Each operator defined for use in the where clause that returns a
   Boolean value MUST evaluate to TRUE, FALSE, or UNKNOWN.  The resource
   under scan is included as a member of the result set if and only if
   the search condition evaluates to TRUE.

   Consult Appendix A for details on the application of three-valued
   logic in query expressions.

5.5.2.  Handling Optional Operators

   If a query contains an operator that is not supported by the server,
   then the server MUST respond with a 422 (Unprocessable Entity) status
   code.

5.5.3.  Treatment of NULL Values

   If a PROPFIND for a property value would yield a non-2xx (see
   [RFC2616], Section 10.2) response for that property, then that
   property is considered NULL.

   NULL values are "less than" all other values in comparisons.

   Empty strings (zero length strings) are not NULL values.  An empty
   string is "less than" a string with length greater than zero.

   The DAV:is-defined operator is defined to test if the value of a
   property is not NULL.



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5.5.4.  Treatment of Properties with mixed/element Content

   Comparisons of properties that do not have simple types (text-only
   content) is out-of-scope for the standard operators defined for DAV:
   basicsearch and therefore is defined to be UNKNOWN (as per
   Appendix A).  For querying the DAV:resourcetype property, see
   Section 5.13.

5.5.5.  Example: Testing for Equality

   The example shows a single operator (DAV:eq) applied in the criteria.

   <d:where>
     <d:eq>
       <d:prop>
         <d:getcontentlength/>
       </d:prop>
       <d:literal>100</d:literal>
     </d:eq>
   </d:where>

5.5.6.  Example: Relative Comparisons

   The example shows a more complex operation involving several
   operators (DAV:and, DAV:eq, DAV:gt) applied in the criteria.  This
   DAV:where expression matches those resources of type "image/gif" over
   4K in size.

   <D:where>
     <D:and>
       <D:eq>
         <D:prop>
           <D:getcontenttype/>
         </D:prop>
         <D:literal>image/gif</D:literal>
       </D:eq>
       <D:gt>
         <D:prop>
           <D:getcontentlength/>
         </D:prop>
         <D:literal>4096</D:literal>
       </D:gt>
     </D:and>
   </D:where>







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5.6.  DAV:orderby

   The DAV:orderby element specifies the ordering of the result set.  It
   contains one or more DAV:order elements, each of which specifies a
   comparison between two items in the result set.  Informally, a
   comparison specifies a test that determines whether one resource
   appears before another in the result set.  Comparisons are applied in
   the order they occur in the DAV:orderby element, earlier comparisons
   being more significant.

   The comparisons defined here use only a single property from each
   resource, compared using the same ordering as the DAV:lt operator
   (ascending) or DAV:gt operator (descending).  If neither direction is
   specified, the default is DAV:ascending.

   In the context of the DAV:orderby element, null values are considered
   to collate before any actual (i.e., non null) value, including
   strings of zero length (this is compatible with [SQL99]).

   The "caseless" attribute may be used to indicate case-sensitivity for
   comparisons (Section 5.18).

5.6.1.  Example of Sorting

   This sort orders first by last name of the author, and then by size,
   in descending order, so that for each author, the largest works
   appear first.

   <d:orderby>
     <d:order>
       <d:prop><r:lastname/></d:prop>
       <d:ascending/>
     </d:order>
     <d:order>
       <d:prop><d:getcontentlength/></d:prop>
       <d:descending/>
     </d:order>
   </d:orderby>

5.7.  Boolean Operators: DAV:and, DAV:or, and DAV:not

   The DAV:and operator performs a logical AND operation on the
   expressions it contains.

   The DAV:or operator performs a logical OR operation on the values it
   contains.

   The DAV:not operator performs a logical NOT operation on the values



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   it contains.

5.8.  DAV:eq

   The DAV:eq operator provides simple equality matching on property
   values.

   The "caseless" attribute may be used with this element
   (Section 5.18).

5.9.  DAV:lt, DAV:lte, DAV:gt, DAV:gte

   The DAV:lt, DAV:lte, DAV:gt, and DAV:gte operators provide
   comparisons on property values, using less-than, less-than or equal,
   greater-than, and greater-than or equal respectively.  The "caseless"
   attribute may be used with these elements (Section 5.18).

5.10.  DAV:literal

   DAV:literal allows literal values to be placed in an expression.

   White space in literal values is significant in comparisons.  For
   consistency with [RFC4918], clients SHOULD NOT specify the attribute
   "xml:space" (Section 2.10 of [XML]) to override this behavior.

   In comparisons, the contents of DAV:literal SHOULD be treated as
   string, with the following exceptions:

   o  when operand for a comparison with a DAV:getcontentlength
      property, it SHOULD be treated as an unsigned integer value (the
      behavior for values not in this format is undefined),

   o  when operand for a comparison with a DAV:creationdate or DAV:
      getlastmodified property, it SHOULD be treated as a date value in
      the ISO-8601 subset defined for the DAV:creationdate property (see
      [RFC4918], Section 15.1; the behavior of values not in this format
      is undefined),

   o  when operand for a comparison with a property for which the type
      is known and when compatible with that type, it MAY be treated
      according to this type.

5.11.  DAV:typed-literal (optional)

   There are situations in which a client may want to force a comparison
   not to be string-based (as defined for DAV:literal).  In these cases,
   a typed comparison can be enforced by using DAV:typed-literal
   instead.



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   <!ELEMENT typed-literal (#PCDATA)>

   The data type is specified using the xsi:type attribute defined in
   [XS1], Section 2.6.1.  If the type is not specified, it defaults to
   "xs:string".

   A server MUST reject a request with an unknown type with a status of
   422 (Unprocessable Entity).  It SHOULD reject a request if the value
   provided in DAV:typed-literal can not be cast to the specified type.

   The comparison evaluates to UNKNOWN if the property value can not be
   cast to the specified datatype (see [XPATHFUNC], Section 17).

5.11.1.  Example for Typed Numerical Comparison

   Consider a set of resources with the dead property "edits" in the
   namespace "http://ns.example.org":

                         +-----+----------------+
                         | URI | property value |
                         +-----+----------------+
                         | /a  | "-1"           |
                         | /b  | "01"           |
                         | /c  | "3"            |
                         | /d  | "test"         |
                         | /e  | (undefined)    |
                         +-----+----------------+

   The expression

   <lt xmlns="DAV:"
     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
     xmlns:xs="http://www.w3.org/2001/XMLSchema">
     <prop><edits xmlns="http://ns.example.org"/></prop>
     <typed-literal xsi:type="xs:integer">3</typed-literal>
   </lt>

   will evaluate to TRUE for the resources "/a" and "/b" (their property
   values can be parsed as type xs:integer, and the numerical comparison
   evaluates to true), to FALSE for "/c" (property value is compatible,
   but numerical comparison evaluates to false) and UNKNOWN for "/d" and
   "/e" (the property either is undefined, or its value can not be
   parsed as xs:integer).

5.12.  Support for Matching xml:lang Attributes on Properties

   The following two optional operators can be used to express
   conditions on the language of a property value (as expressed using



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   the xml:lang attribute).

5.12.1.  DAV:language-defined (optional)

   <!ELEMENT language-defined (prop)>

   This operator evaluates to TRUE if the language for the value of the
   given property is known, FALSE if it isn't and UNKNOWN if the
   property itself is not defined.

5.12.2.  DAV:language-matches (optional)

   <!ELEMENT language-matches (prop, literal)>

   This operator evaluates to TRUE if the language for the value of the
   given property is known and matches the language name given in the
   <literal> element, FALSE if it doesn't match and UNKNOWN if the
   property itself is not defined.

   Languages are considered to match if they are the same, or if the
   language of the property value is a sublanguage of the language
   specified in the <literal> element (see [XPATH], Section 4.3, "lang
   function").

5.12.3.  Example of Language-Aware Matching

   The expression below will evaluate to TRUE if the property "foobar"
   exists and its language is either unknown, English or a sublanguage
   of English.

   <or xmlns="DAV:">
     <not>
       <language-defined>
         <prop><foobar/></prop>
       </language-defined>
     </not>
     <language-matches>
       <prop><foobar/></prop>
       <literal>en</literal>
     </language-matches>
   </or>

5.13.  DAV:is-collection

   The DAV:is-collection operator allows clients to determine whether a
   resource is a collection (that is, whether its DAV:resourcetype
   element contains the element DAV:collection).




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   Rationale: This operator is provided in lieu of defining generic
   structure queries, which would suffice for this and for many more
   powerful queries, but seems inappropriate to standardize at this
   time.

5.13.1.  Example of DAV:is-collection

   This example shows a search criterion that picks out all and only the
   resources in the scope that are collections.

   <where xmlns="DAV:">
     <is-collection/>
   </where>

5.14.  DAV:is-defined

   The DAV:is-defined operator allows clients to determine whether a
   property is defined on a resource.  The meaning of "defined on a
   resource" is found in Section 5.5.3.

   Example:

   <d:is-defined>
     <d:prop><x:someprop/></d:prop>
   </d:is-defined>

5.15.  DAV:like

   The DAV:like is an optional operator intended to give simple
   wildcard-based pattern matching ability to clients.

   The operator takes two arguments.

   The first argument is a DAV:prop element identifying a single
   property to evaluate.

   The second argument is a DAV:literal element that gives the pattern
   matching string.













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5.15.1.  Syntax for the Literal Pattern

   pattern       = [wildcard] 0*( text [wildcard] )

   wildcard      = exactlyone / zeroormore
   text          = 1*( character / escapeseq )

   exactlyone    = "_"
   zeroormore    = "%"
   escapechar    = "\"
   escapeseq     = escapechar ( exactlyone / zeroormore / escapechar )

   ; character: see [XML], Section 2.2, minus wildcard / escapechar
   character     = HTAB / LF / CR ; whitespace
   character     =/ %x20-24 / %x26-5B / %x5D-5E / %x60-D7FF
   character     =/ %xE000-FFFD / %x10000-10FFFF

   (Note that the ABNF above is defined in terms of Unicode code points
   ([UNICODE5]); when an query is transmitted as XML document WebDAV,
   these characters are typically encoded in UTF-8 or UTF-16.)

   The value for the literal is composed of wildcards separated by
   segments of text.  Wildcards may begin or end the literal.

   The "_" wildcard matches exactly one character.

   The "%" wildcard matches zero or more characters

   The "\" character is an escape sequence so that the literal can
   include "_" and "%".  To include the "\" character in the pattern,
   the escape sequence "\\" is used.

5.15.2.  Example of DAV:like

   This example shows how a client might use DAV:like to identify those
   resources whose content type was a subtype of image.

   <D:where>
     <D:like caseless="yes">
       <D:prop><D:getcontenttype/></D:prop>
       <D:literal>image/%</D:literal>
     </D:like>
   </D:where>

5.16.  DAV:contains

   The DAV:contains operator is an optional operator that provides
   content-based search capability.  This operator implicitly searches



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   against the text content of a resource, not against content of
   properties.  The DAV:contains operator is intentionally not overly
   constrained, in order to allow the server to do the best job it can
   in performing the search.

   The DAV:contains operator evaluates to a Boolean value.  It evaluates
   to TRUE if the content of the resource satisfies the search.
   Otherwise, it evaluates to FALSE.

   Within the DAV:contains XML element, the client provides a phrase: a
   single word or whitespace delimited sequence of words.  Servers MAY
   ignore punctuation in a phrase.  Case-sensitivity is at the
   discretion of the server implementation.

   The following non-exhaustive list enumerate things that may or may
   not be done as part of the search: Phonetic methods such as "soundex"
   may or may not be used.  Word stemming may or may not be performed.
   Thesaurus expansion of words may or may not be done.  Right or left
   truncation may or may not be performed.  The search may be case
   insensitive or case sensitive.  The word or words may or may not be
   interpreted as names.  Multiple words may or may not be required to
   be adjacent or "near" each other.  Multiple words may or may not be
   required to occur in the same order.  Multiple words may or may not
   be treated as a phrase.  The search may or may not be interpreted as
   a request to find documents "similar" to the string operand.
   Character canonicalization such as that done by the Unicode collation
   algorithm may or may not be applied.

5.16.1.  Result Scoring (DAV:score Element)

   Servers SHOULD indicate scores for the DAV:contains condition by
   adding a DAV:score XML element to the DAV:response element.  Its
   value is defined only in the context of a particular query result.
   The value is a string representing the score, an integer from zero to
   10000 inclusive, where a higher value indicates a higher score (e.g.
   more relevant).

   Modified DTD fragment for DAV:propstat:

   <!ELEMENT response (href, ((href*, status)|(propstat+)),
                       responsedescription?, score?) >
   <!ELEMENT score    (#PCDATA) >

   Clients should note that, in general, it is not meaningful to compare
   the numeric values of scores from two different query results unless
   both were executed by the same underlying search system on the same
   collection of resources.




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5.16.2.  Ordering by Score

   To order search results by their score, the DAV:score element may be
   added as child to the DAV:orderby element (in place of a DAV:prop
   element).

5.16.3.  Examples

   The example below shows a search for the phrase "Peter Forsberg".

   Depending on its support for content-based searching, a server MAY
   treat this as a search for documents that contain the words "Peter"
   and "Forsberg".

   <D:where>
     <D:contains>Peter Forsberg</D:contains>
   </D:where>

   The example below shows a search for resources that contain "Peter"
   and "Forsberg".

   <D:where>
     <D:and>
       <D:contains>Peter</D:contains>
       <D:contains>Forsberg</D:contains>
     </D:and>
   </D:where>

5.17.  Limiting the Result Set

   <!ELEMENT limit (nresults) >
   <!ELEMENT nresults (#PCDATA)> <!-- only digits -->

   The DAV:limit XML element contains requested limits from the client
   to limit the size of the reply or amount of effort expended by the
   server.  The DAV:nresults XML element contains a requested maximum
   number of DAV:response elements to be returned in the response body.
   The server MAY disregard this limit.  The value of this element is an
   unsigned integer.

5.17.1.  Relationship to Result Ordering

   If the result set is both limited by DAV:limit and ordered according
   to DAV:orderby, the results that are included in the response
   document must be those that order highest.






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5.18.  The 'caseless' XML Attribute

   The "caseless" attribute allows clients to specify caseless matching
   behavior instead of character-by-character matching for DAV:
   basicsearch operators.

   The possible values for "caseless" are "yes" or "no".  The default
   value is server-specified.  Caseless matching SHOULD be implemented
   as defined in Section 5.18 of the Unicode Standard ([UNICODE5]).

   Support for the "caseless" attribute is optional.  A server should
   respond with a status of 422 if it is used but cannot be supported.

5.19.  Query Schema for DAV:basicsearch

   The DAV:basicsearch grammar defines a search criteria that is a
   Boolean-valued expression, and allows for an arbitrary set of
   properties to be included in the result record.  The result set may
   be sorted on a set of property values.  Accordingly the DTD for
   schema discovery for this grammar allows the server to express:

   1.  the set of properties that may be either searched, returned, or
       used to sort, and a hint about the data type of such properties

   2.  the set of optional operators defined by the resource.

5.19.1.  DTD for DAV:basicsearch QSD

   <!ELEMENT basicsearchschema  (properties, operators)>
   <!ELEMENT any-other-property EMPTY>
   <!ELEMENT properties         (propdesc*)>
   <!ELEMENT propdesc           ((prop|any-other-property), datatype?,
                                 searchable?, selectable?, sortable?,
                                 caseless?)>
   <!ELEMENT operators          (opdesc*)>
   <!ELEMENT opdesc             ANY>
   <!ATTLIST opdesc             allow-pcdata (yes|no) #IMPLIED>
   <!ELEMENT operand-literal    EMPTY>
   <!ELEMENT operand-typed-literal EMPTY>
   <!ELEMENT operand-property   EMPTY>

   The DAV:properties element holds a list of descriptions of
   properties.

   The DAV:operators element describes the optional operators that may
   be used in a DAV:where element.





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5.19.2.  DAV:propdesc Element

   Each instance of a DAV:propdesc element describes the property or
   properties in the DAV:prop element it contains.  All subsequent
   elements are descriptions that apply to those properties.  All
   descriptions are optional and may appear in any order.  Servers
   SHOULD support all the descriptions defined here, and MAY define
   others.

   DASL defines five descriptions.  The first, DAV:datatype, provides a
   hint about the type of the property value, and may be useful to a
   user interface prompting for a value.  The remaining four (DAV:
   searchable, DAV:selectable, DAV:sortable, and DAV:caseless) identify
   portions of the query (DAV:where, DAV:select, and DAV:orderby,
   respectively).  If a property has a description for a section, then
   the server MUST allow the property to be used in that section.  These
   descriptions are optional.  If a property does not have such a
   description, or is not described at all, then the server MAY still
   allow the property to be used in the corresponding section.

5.19.2.1.  DAV:any-other-property

   This element can be used in place of DAV:prop to describe properties
   of WebDAV properties not mentioned in any other DAV:prop element.
   For instance, this can be used to indicate that all other properties
   are searchable and selectable without giving details about their
   types (a typical scenario for dead properties).

5.19.3.  The DAV:datatype Property Description

   The DAV:datatype element contains a single XML element that provides
   a hint about the domain of the property, which may be useful to a
   user interface prompting for a value to be used in a query.  Data
   types are identified by an element name.  Where appropriate, a server
   SHOULD use the simple data types defined in [XS2].

   <!ELEMENT datatype ANY >

   Examples from [XS2], Section 3:

                 +----------------+---------------------+
                 | Qualified name | Example             |
                 +----------------+---------------------+
                 | xs:boolean     | true, false, 1, 0   |
                 | xs:string      | Foobar              |
                 | xs:dateTime    | 1994-11-05T08:15:5Z |
                 | xs:float       | .314159265358979E+1 |




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                 | xs:integer     | -259, 23            |
                 +----------------+---------------------+

   If the data type of a property is not given, then the data type
   defaults to xs:string.

5.19.4.  The DAV:searchable Property Description

   <!ELEMENT searchable EMPTY>

   If this element is present, then the server MUST allow this property
   to appear within a DAV:where element where an operator allows a
   property.  Allowing a search does not mean that the property is
   guaranteed to be defined on every resource in the scope, it only
   indicates the server's willingness to check.

5.19.5.  The DAV:selectable Property Description

   <!ELEMENT selectable EMPTY>

   This element indicates that the property may appear in the DAV:select
   element.

5.19.6.  The DAV:sortable Property Description

   This element indicates that the property may appear in the DAV:
   orderby element.

   <!ELEMENT sortable EMPTY>

5.19.7.  The DAV:caseless Property Description

   This element only applies to properties whose data type is "xs:
   string" and derived data types as per the DAV:datatype property
   description.  Its presence indicates that compares performed for
   searches, and the comparisons for ordering results on the string
   property will be caseless (the default is character-by-character).

   <!ELEMENT caseless EMPTY>

5.19.8.  The DAV:operators XML Element

   The DAV:operators element describes every optional operator supported
   in a query.  (Mandatory operators are not listed since they are
   mandatory and permit no variation in syntax.).  All optional
   operators that are supported MUST be listed in the DAV:operators
   element.




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   The listing for an operator, contained in an DAV:opdesc element,
   consists of the operator (as an empty element), followed by one
   element for each operand.  The operand MUST be either DAV:operand-
   property, DAV:operand-literal or DAV:operand-typed-literal, which
   indicate that the operand in the corresponding position is a
   property, a literal value or a typed literal value, respectively.  If
   an operator is polymorphic (allows more than one operand syntax) then
   each permitted syntax MUST be listed separately.

   The DAV:opdesc element MAY have a "allow-pcdata" attribute
   (defaulting to "no").  A value of "yes" indicates that the operator
   can contain character data, as it is the case with DAV:contains (see
   Section 5.16).  Definition of additional operators using this format
   is NOT RECOMMENDED.

   <operators xmlns='DAV:'>
     <opdesc>
       <like/><operand-property/><operand-literal/>
     </opdesc>
   </operators>































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5.19.9.  Example of Query Schema for DAV:basicsearch

   <D:basicsearchschema xmlns:D="DAV:"
     xmlns:xs="http://www.w3.org/2001/XMLSchema"">
     <D:properties>
       <D:propdesc>
         <D:prop><D:getcontentlength/></D:prop>
         <D:datatype><xs:nonNegativeInteger/></D:datatype>
         <D:searchable/><D:selectable/><D:sortable/>
       </D:propdesc>
       <D:propdesc>
         <D:prop><D:getcontenttype/><D:displayname/></D:prop>
         <D:searchable/><D:selectable/><D:sortable/>
       </D:propdesc>
       <D:propdesc>
         <D:prop><fstop xmlns="http://jennicam.org"/></D:prop>
         <D:selectable/>
       </D:propdesc>
       <D:propdesc>
         <D:any-other-property/>
         <D:searchable/><D:selectable/>
       </D:propdesc>
     </D:properties>
     <D:operators>
       <D:opdesc>
         <D:like/><D:operand-property/><D:operand-literal/>
       </D:opdesc>
       <D:opdesc allow-pcdata="yes">
         <D:contains/>
       </D:opdesc>
     </D:operators>
   </D:basicsearchschema>

   This response lists four properties.  The data type of the last three
   properties is not given, so it defaults to xs:string.  All are
   selectable, and the first three may be searched.  All but the last
   may be used in a sort.  Of the optional DAV operators, DAV:contains
   and DAV:like are supported.

   Note: The schema discovery defined here does not provide for
   discovery of supported values of the "caseless" attribute.  This may
   require that the reply also list the mandatory operators.


6.  Internationalization Considerations

   Properties may be language-tagged using the xml:lang attribute (see
   [RFC4918], Section 4.3).  The optional operators DAV:language-defined



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   (Section 5.12.1) and DAV:language-matches (Section 5.12.2) allow to
   express conditions on the language tagging information.


7.  Security Considerations

   This section is provided to detail issues concerning security
   implications of which DASL applications need to be aware.  All of the
   security considerations of HTTP/1.1 ([RFC2616] and WebDAV ([RFC4918])
   also apply to DASL.  In addition, this section will include security
   risks inherent in searching and retrieval of resource properties and
   content.

   A query MUST NOT allow clients to retrieve information that wouldn't
   have been available through the GET or PROPFIND methods in the first
   place.  In particular:

   o  Query constraints on WebDAV properties for which the client does
      not have read access need to be evaluated as if the property did
      not exist (see Section 5.5.3).

   o  Query constraints on content (as with DAV:contains, defined in
      Section 5.16) for which the client does not have read access need
      to be evaluated as if a GET would return a 4xx status code.

   A server should prepare for denial of service attacks.  For example a
   client may issue a query for which the result set is expensive to
   calculate or transmit because many resources match or must be
   evaluated.

7.1.  Implications of XML External Entities

   XML supports a facility known as "external entities", defined in
   Section 4.2.2 of [XML], which instruct an XML processor to retrieve
   and perform an inline include of XML located at a particular URI.  An
   external XML entity can be used to append or modify the document type
   declaration (DTD) associated with an XML document.  An external XML
   entity can also be used to include XML within the content of an XML
   document.  For non-validating XML, such as the XML used in this
   specification, including an external XML entity is not required by
   [XML].  However, [XML] does state that an XML processor may, at its
   discretion, include the external XML entity.

   External XML entities have no inherent trustworthiness and are
   subject to all the attacks that are endemic to any HTTP GET request.
   Furthermore, it is possible for an external XML entity to modify the
   DTD, and hence affect the final form of an XML document, in the worst
   case significantly modifying its semantics, or exposing the XML



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   processor to the security risks discussed in [RFC3023].  Therefore,
   implementers must be aware that external XML entities should be
   treated as untrustworthy.

   There is also the scalability risk that would accompany a widely
   deployed application which made use of external XML entities.  In
   this situation, it is possible that there would be significant
   numbers of requests for one external XML entity, potentially
   overloading any server which fields requests for the resource
   containing the external XML entity.


8.  Scalability

   Query grammars are identified by URIs.  Applications SHOULD not
   attempt to retrieve these URIs even if they appear to be retrievable
   (for example, those that begin with "http://")


9.  IANA Considerations

   This document uses the namespace defined in Section 21 of [RFC4918]
   for XML elements.

9.1.  HTTP Headers

   This document specifies the HTTP header listed below, to be added to
   the HTTP header registry defined in [RFC3864].

9.1.1.  DASL

   Header field name:  DASL

   Applicable protocol:  http

   Status:  Experimental

   Author/Change controller:  IETF

   Specification document:  this specification (Section 3.2)


10.  Contributors

   This document is based on prior work on the DASL protocol done by the
   WebDAV DASL working group until the year 2000 -- namely by Alan
   Babich, Jim Davis, Rick Henderson, Dale Lowry, Saveen Reddy and
   Surendra Reddy.



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11.  Acknowledgements

   This document has benefited from thoughtful discussion by Lisa
   Dusseault, Javier Godoy, Sung Kim, Chris Newman, Elias Sinderson,
   Martin Wallmer, Keith Wannamaker, Jim Whitehead and Kevin Wiggen.


12.  References

12.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2616]  Fielding, R., Gettys, J., Mogul, J., Nielsen, H.,
              Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
              Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.

   [RFC3023]  Makoto, M., St.Laurent, S., and D. Kohn, "XML Media
              Types", RFC 3023, January 2001.

   [RFC3253]  Clemm, G., Amsden, J., Ellison, T., Kaler, C., and J.
              Whitehead, "Versioning Extensions to WebDAV", RFC 3253,
              March 2002.

   [RFC3744]  Clemm, G., Reschke, J., Sedlar, E., and J. Whitehead, "Web
              Distributed Authoring and Versioning (WebDAV) Access
              Control Protocol", RFC 3744, May 2004.

   [RFC3986]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
              Resource Identifier (URI): Generic Syntax", STD 66,
              RFC 3986, January 2005.

   [RFC4918]  Dusseault, L., Ed., "HTTP Extensions for Web Distributed
              Authoring and Versioning (WebDAV)", RFC 4918, June 2007.

   [RFC5234]  Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
              Specifications: ABNF", STD 68, RFC 5234, January 2008.

   [XML]      Bray, T., Paoli, J., Sperberg-McQueen, C., Maler, E., and
              F. Yergeau, "Extensible Markup Language (XML) 1.0 (Fourth
              Edition)", W3C REC-xml-20060816, August 2006,
              <http://www.w3.org/TR/2006/REC-xml-20060816>.

   [XPATH]    Clark, J. and S. DeRose, "XML Path Language (XPath)
              Version 1.0", W3C REC-xpath-19991116, November 1999,
              <http://www.w3.org/TR/1999/REC-xpath-19991116>.




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   [XPATHFUNC]
              Malhotra, A., Melton, J., and N. Walsh, "XQuery 1.0 and
              XPath 2.0 Functions and Operators", W3C REC-xpath-
              functions-20070123, January 2007,
              <http://www.w3.org/TR/2007/REC-xpath-functions-20070123/>.

   [XS1]      Thompson, H., Beech, D., Maloney, M., Mendelsohn, N., and
              World Wide Web Consortium, "XML Schema Part 1:
              Structures", W3C REC-xmlschema-1-20041028, October 2004,
              <http://www.w3.org/TR/2004/REC-xmlschema-1-20041028/>.

   [XS2]      Biron, P., Malhotra, A., and World Wide Web Consortium,
              "XML Schema Part 2: Datatypes Second Edition", W3C REC-
              xmlschema-2-20041028, October 2004,
              <http://www.w3.org/TR/2004/REC-xmlschema-2-20041028/>.

12.2.  Informative References

   [BCP47]    Phillips, A. and M. Davis, "Matching of Language Tags",
              BCP 47, RFC 4647, September 2006.

   [DASL]     Reddy, S., Lowry, D., Reddy, S., Henderson, R., Davis, J.,
              and A. Babich, "DAV Searching & Locating",
              draft-ietf-dasl-protocol-00 (work in progress), July 1999.

   [DASLREQ]  Davis, J., Reddy, S., and J. Slein, "Requirements for DAV
              Searching and Locating", February 1999, <http://
              www.webdav.org/dasl/requirements/
              draft-dasl-requirements-01.html>.

              This is an updated version of the Internet Draft
              "draft-ietf-dasl-requirements-00", but obviously never was
              submitted to the IETF.

   [RFC3864]  Klyne, G., Nottingham, M., and J. Mogul, "Registration
              Procedures for Message Header Fields", BCP 90, RFC 3864,
              September 2004.

   [RFC4437]  Whitehead, J., Clemm, G., and J. Reschke, Ed., "Web
              Distributed Authoring and Versioning (WebDAV)
              Redirect Reference Resources", RFC 4437, March 2006.

   [RFC4790]  Newman, C., Duerst, M., and A. Gulbrandsen, "Internet
              Application Protocol Collation Registry", RFC 4790,
              March 2007.

   [SQL99]    Milton, J., "Database Language SQL Part 2: Foundation
              (SQL/Foundation)", ISO ISO/IEC 9075-2:1999 (E), July 1999.



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   [UNICODE5]
              The Unicode Consortium, "The Unicode Standard - Version
              5.0", Addison-Wesley , November 2006,
              <http://www.unicode.org/versions/Unicode5.0.0/>.

              ISBN 0321480910 [1]

   [draft-ietf-webdav-bind]
              Clemm, G., Crawford, J., Reschke, J., Ed., and J.
              Whitehead, "Binding Extensions to Web Distributed
              Authoring and Versioning (WebDAV)",
              draft-ietf-webdav-bind-20 (work in progress),
              November 2007.

URIs

   [1]  <urn:isbn:0321480910>


Appendix A.  Three-Valued Logic in DAV:basicsearch

   ANSI standard three valued logic is used when evaluating the search
   condition (as defined in the ANSI standard SQL specifications, for
   example in ANSI X3.135-1992, section 8.12, pp. 188-189, section 8.2,
   p. 169, General Rule 1)a), etc.).

   ANSI standard three valued logic is undoubtedly the most widely
   practiced method of dealing with the issues of properties in the
   search condition not having a value (e.g., being null or not defined)
   for the resource under scan, and with undefined expressions in the
   search condition (e.g., division by zero, etc.).  Three valued logic
   works as follows.

   Undefined expressions are expressions for which the value of the
   expression is not defined.  Undefined expressions are a completely
   separate concept from the truth value UNKNOWN, which is, in fact,
   well defined.  Property names and literal constants are considered
   expressions for purposes of this section.  If a property in the
   current resource under scan has not been set to a value, then the
   value of that property is undefined for the resource under scan.
   DASL 1.0 has no arithmetic division operator, but if it did, division
   by zero would be an undefined arithmetic expression.

   If any subpart of an arithmetic, string, or datetime subexpression is
   undefined, the whole arithmetic, string, or datetime subexpression is
   undefined.

   There are no manifest constants to explicitly represent undefined



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   number, string, or datetime values.

   Since a Boolean value is ultimately returned by the search condition,
   arithmetic, string, and datetime expressions are always arguments to
   other operators.  Examples of operators that convert arithmetic,
   string, and datetime expressions to Boolean values are the six
   relational operators ("greater than", "less than", "equals", etc.).
   If either or both operands of a relational operator have undefined
   values, then the relational operator evaluates to UNKNOWN.
   Otherwise, the relational operator evaluates to TRUE or FALSE,
   depending upon the outcome of the comparison.

   The Boolean operators DAV:and, DAV:or and DAV:not are evaluated
   according to the following rules:

   not UNKNOWN = UNKNOWN

   UNKNOWN and TRUE = UNKNOWN

   UNKNOWN and FALSE = FALSE

   UNKNOWN and UNKNOWN = UNKNOWN

   UNKNOWN or TRUE = TRUE

   UNKNOWN or FALSE = UNKNOWN

   UNKNOWN or UNKNOWN = UNKNOWN


Appendix B.  Candidates for Future Protocol Extensions

   This Section summarizes issues which have been raised during the
   development of this specification, but for which no resolution could
   be found with the constraints in place.  Future revisions of this
   specification should revisit these issues, though.

B.1.  Collation Support

   Matching and sorting of textual data relies on collations.  With
   respect to WebDAV SEARCH, a combination of various design approaches
   could be used:

   o  Require server support for specific collations.

   o  Require that the server can advertise which collations it
      supports.




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   o  Allow a client to select the collation to be used.

   In practice, the current implementations of WebDAV SEARCH usually
   rely on backends they do not control, and for which collation
   information may not be available.  To make things worse,
   implementations of the DAV:basicsearch grammar frequently need to
   combine data from multiple underlying stores (such as properties and
   full text content), and thus collation support may vary based on the
   operator or property.

   Another open issue is what collation formalism to support.  At the
   time of this writing, the two specifications below seem to provide
   the necessary framework and thus may be the base for future work on
   collation support in WebDAV SEARCH:

   1.  "Internet Application Protocol Collation Registry" ([RFC4790]).

   2.  "XQuery 1.0 and XPath 2.0 Functions and Operators" ([XPATHFUNC],
       Section 7.3.1).

B.2.  Count

   DAV:basicsearch does not allow a request that returns the count of
   matching resources.

   A protocol extension would need to extend DAV:select, and also modify
   the DAV:multistatus response format.

B.3.  Diagnostics for Unsupported Queries

   There are many reasons why a given query may not be supported by a
   server.  Query Schema Discovery (Section 4) can be used to discover
   some constraints, but not all.

   Future revisions should consider the introduction of specific
   condition codes ([RFC4918], Section 16) to these situations.

B.4.  Language Matching

   Section 5.12.2 defines language matching in terms of the XPath "lang"
   function ([XPATH], Section 4.3).  Future revisions should consider
   building on [BCP47] instead.

B.5.  Matching Media Types

   Matching media types using the DAV:getcontenttype property and the
   DAV:like operator is hard due to DAV:getcontenttype also allowing
   parameters.  A new operator specifically designed for the purpose of



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   matching media types probably would simplify things a lot.  See <http
   ://lists.w3.org/Archives/Public/www-webdav-dasl/2003OctDec/0109.html>
   for a specific proposal.

B.6.  Query by Name

   DAV:basicsearch operates on the properties (and optionally the
   contents) of resources, and thus doesn't really allow matching on
   parts of the resource's URI.  See <http://lists.w3.org/Archives/
   Public/www-webdav-dasl/2003OctDec/0100.html> for a proposed extension
   covering this use case.

B.7.  Result Paging

   A frequently discussed feature is the ability to specifically request
   the "next" set of results, when either the server decided to truncate
   the result, or the client explicitly asked for a limited set (for
   instance, using the DAV:limit element defined in Section 5.17).

   In this case, it would be desirable if the server could keep the full
   query result, and provide a new URI identifying a separate result
   resource, allowing the client to retrieve additional data through GET
   requests, and remove the result through a DELETE request.

B.8.  Search Scope Discovery

   Given a Search Arbiter resource, there's currently no way to discover
   programmatically the supported sets of search scopes.  Future
   revisions of this specification could specify a scope discovery
   mechanism, similar to the Query Schema Discovery defined in
   Section 4.


Appendix C.  Change Log (to be removed by RFC Editor before publication)

C.1.  From draft-davis-dasl-protocol-xxx

   Feb 14, 1998  Initial Draft

   Feb 28, 1998  Referring to DASL as an extension to HTTP/1.1 rather
      than DAV.
      Added new sections "Notational Conventions", "Protocol Model",
      "Security Considerations".
      Changed section 3 to "Elements of Protocol".
      Added some stuff to introduction.
      Added "result set" terminology.
      Added "IANA Considerations".




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   Mar 9, 1998  Moved sub-headings of "Elements of Protocol" to first
      level and removed "Elements of Protocol" Heading.
      Added an sentence in introduction explaining that this is a
      "sketch" of a protocol.

   Mar 11, 1998  Added orderby, data typing, three valued logic, query
      schema property, and element definitions for schema for
      basicsearch.

   April 8, 1998  - made changes based on last week's DASL BOF.

   May 8, 1998  Removed most of DAV:searcherror; converted to DAV:
      searchredirect
      Altered DAV:basicsearch grammar to use avoid use of ANY in DTD

   June 17, 1998  -Added details on Query Schema Discovery
      -Shortened list of data types

   June 23, 1998  moved data types before change history
      rewrote the data types section
      removed the casesensitive element and replace with the
      casesensitive attribute
      added the casesensitive attribute to the DTD for all operations
      that might work on a string

   Jul 20, 1998  A series of changes.  See Author's meeting minutes for
      details.

   July 28, 1998  Changes as per author's meeting.  QSD uses SEARCH, not
      PROPFIND.
      Moved text around to keep concepts nearby.
      Boolean literals are 1 and 0, not T and F.
      contains changed to contentspassthrough.
      Renamed rank to score.

   July 28, 1998  Added Dale Lowry as Author

   September 4, 1998  Added 422 as response when query lists
      unimplemented operators.
      DAV:literal declares a default value for xml:space, 'preserve'
      (see XML spec, section 2.10)
      moved to new XML namespace syntax

   September 22, 1998  Changed "simplesearch" to "basicsearch"
      Changed isnull to isdefined
      Defined NULLness as having a 404 or 403 response
      used ENTITY syntax in DTD
      Added redirect



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   October 9, 1998  Fixed a series of typographical and formatting
      errors.
      Modified the section of three-valued logic to use a table rather
      than a text description of the role of UNKNOWN in expressions.

   November 2, 1998  Added the DAV:contains operator.
      Removed the DAV:contentpassthrough operator.

   November 18, 1998  Various author comments for submission

   June 3, 1999  Cosmetic and minor editorial changes only.  Fix nits
      reported by Jim Whitehead in email of April 26, 1999.  Converted
      to HTML from Word 97, manually.

   April 20, 2000  Removed redirection feature, since 301/302 suffices.
      Removed Query Schema Discovery (former chapter 4).  Everyone
      agrees this is a useful feature, but it is apparently too
      difficult to define at this time, and it is not essential for
      DASL.

C.2.  since start of draft-reschke-webdav-search

   October 09, 2001  Added Julian Reschke as author.
      Chapter about QSD re-added.
      Formatted into RFC2629-compliant XML document.
      Added first comments.
      ID version number kicked up to draft-dasl-protocol-03.

   October 17, 2001  Updated address information for Jim Davis.
      Added issue of datatype vocabularies.
      Updated issue descriptions for grammar discovery, added issues on
      query schema DTD.
      Fixed typos in XML examples.

   December 17, 2001  Re-introduced split between normative and non-
      normative references.

   January 05, 2002  Version bumped up to 04.  Started work on resolving
      the issues identified in the previous version.

   January 14, 2002  Fixed some XML typos.

   January 22, 2002  Closed issues naming-of-elements.  Fixed query
      search DTD and added option to discover properties of "other"
      (non-listed) properties.






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   January 25, 2002  Changed into private submission and added reference
      to historic DASL draft.  Marked reference to DASL requirements
      non-normative.
      Updated reference to latest deltav spec.

   January 29, 2002  Added feedback from and updated contact info for
      Alan Babich.
      Included open issues collected in
      http://www.webdav.org/dasl/protocol/issues.html.

   February 8, 2002  Made sure that all artwork fits into 72 characters
      wide text.

   February 18, 2002  Changed Insufficient storage handling
      (multistatus).  Moved is-collection to operators and added to DTD.
      Made scope/depth mandatory.

   February 20, 2002  Updated reference to SQL99.

   February 28, 2002  "Non-normative References" -> "Informative
      References".  Abstract updated.  Consistently specify a charset
      when using text/xml (no change bars).  Do not attempt to define
      PROPFIND's entity encoding (take out specific references to text/
      xml).  Remove irrelevant headers (Connection:) from examples (no
      change bars).  Added issue on querying based on DAV:href.  Updated
      introduction to indicate relationship to DASL draft.  Updated HTTP
      reference from RFC2068 to RFC2616.  Updated XML reference to XML
      1.0 2nd edition.

   March 1, 2002  Removed superfluous namespace decl in 2.4.2.  Reopened
      JW14 and suggest to drop xml:space support.

   March 3, 2002  Removed "xml:space" feature on DAV:literal.  Added
      issue about string comparison vs. collations vs. xml:lang.
      Updated some of the open issues with details from JimW's original
      mail in April 1999.  Resolved scope vs relative URI references.
      Resolved issues about DAV:ascending (added to index) and the BNF
      for DAV:like (changed "octets" to "characters").

   March 8, 2002  Updated reference to DeltaV (now RFC3253).  Added
      Martin Wallmer's comments, moved JW5 into DAV:basicsearch section.

   March 11, 2002  Closed open issues regaring the type of search
      arbiters (JW3) and their discovery (JW9).  Rephrased requirements
      on multistatus response bodies (propstat only if properties were
      selected, removed requirement for responsedescription).





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   March 23, 2002  RFC2376 -> RFC3023.  Added missing first names of
      authors.  OPTIONS added to example for DAV:supported-method-set.

C.3.  since draft-reschke-webdav-search-00

   March 29, 2002  Abstract doesn't refer to DASL WG anymore.

   April 7, 2002  Fixed section title (wrong property name supported-
      search-grammar-set.  Changed DAV:casesensitve to "casesensitive"
      (it wasn't in the DAV: namespace after all).

   May 28, 2002  Updated some issues with Jim Davis's comments.

   June 10, 2002  Added proposal for different method for query schema
      discovery, not using pseudo-properties.

   June 25, 2002  QSD marshalling rewritten.  Added issue "isdefined-
      optional".

C.4.  since draft-reschke-webdav-search-01

   July 04, 2002  Added issue "scope-collection".

   July 08, 2002  Closed issue "scope-collection".

   August 12, 2002  Added issues "results-vs-binds" and "select-
      allprop".

   October 22, 2002  Added issue "undefined-expressions".

   November 18, 2002  Changed example host names (no change tracking).

   November 25, 2002  Updated issue "DB2/DB7".  Closed issues "undefined
      expressions", "isdefined-optional" and "select-allprop".

C.5.  since draft-reschke-webdav-search-02

   November 27, 2002  Added issues "undefined-properties", "like-
      exactlyone" and "like-wildcard-adjacent".  Closed issue "query-on-
      href".  Added acknowledgments section.

   November 28, 2002  Closed issue "like-exactlyone".  Added issue
      "mixed-content-properties".

   December 14, 2002  Closed issues "undefined-properties", "results-vs-
      binds", "mixed-content-properties".  Updated issue "like-wildcard-
      adjacent".  Added informative reference to BIND draft.  Updated
      reference to ACL draft.



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   January 9, 2003  Removed duplicate section on invalid scopes.  Added
      comments to some open issues.  Closed issues JW25/26, score-
      pseudo-property and null-ordering.

   January 10, 2003  Issue limit-vs-ordering plus resolution.  Closed
      issue JW17/JW24b.

   January 14, 2003  New issue order-precedence.  Started resolution of
      DB2/DB7.

   January 15, 2003  Started spec of DAV:typed-literal.

   January 17, 2003  Fix one DAV:like/DAV:getcontenttype example (add /
      to like expression, make case-insensitive).

   January 28, 2003  Update issue(s) result-truncation, JW24d.  Fixed
      response headers in OPTIONS example.  Added issue qsd-optional.
      Closed issue(s) order-precedence, case-insensitivity-name.

   February 07, 2003  Added issue scope-vs-versions. score-pseudo-
      property: allow DAV:orderby to explicitly specify DAV:score.

C.6.  since draft-reschke-webdav-search-03

   April 24, 2003  Fixed two "?" vs "_" issues (not updated in last
      draft).

   June 13, 2003  Improve index.

C.7.  since draft-reschke-webdav-search-04

   July 7, 2003  Typo fixed (propstat without status element).

   August 11, 2003  Remove superfluous IP and copyright sections.

   September 09, 2003  Added issues "2.4-multiple-uris" and "5.1-name-
      filtering".

   October 06, 2003  Fix misplaced section end in 5.11, add table
      formatting.  Enhance table formatting in 5.18.3.  Updated ACL and
      BIND references.  Added XPATH reference.  Closed issue JW24d by
      adding new optional operators.  Updated more open issues, added
      issues from January meeting.  Add K. Wiggen to Acknowledgements.
      Add Contributors section for the authors of the original draft.
      Close issue "scope-vs-versions" (optional feature added).  Close
      (new) issue "1.3-import-DTD-terminology".  Add issue "1.3-import-
      requirements-terminology".




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   October 07, 2003  Typos fixed.  Moved statement about DAV: namespace
      usage into separate (sub-)section.  Closed "1.3-import-
      requirements-terminology".  Update I18N Considerations with new
      xml:lang support info (see issue JW24d).  Close issue "DB2/DB7"
      (remaining typing issues are now summarized in issue "typed-
      literal").  Fix misplaced section end in section 7.  Started
      change to use RFC3253-style method definitions and error
      marshalling.

   October 08, 2003  Remove obsolete language that allowed reporting
      invalid scopes and such inside multistatus.  Add new issue "5.4.2-
      scope-vs-redirects".

C.8.  since draft-reschke-webdav-search-05

   October 11, 2003  Separate DAV:basicsearch DTD into separate figures
      for better maintainability.  Update DTD with language-* operators
      and typed-literal element (optional).

   October 14, 2003  Close issue "5.4.2-multiple-scope".

   November 04, 2003  Update reference from CaseMap to UNICODE4, section
      5.18.

   November 16, 2003  Updated issue "5.1-name-filtering".

   November 24, 2003  Reformatted scope description (collection vs. non-
      collection).

   November 30, 2003  Add issue "5_media_type_match".

   February 6, 2004  Updated all references.

C.9.  since draft-reschke-webdav-search-06

   July 05, 2004  Fix table in Appendix "Three-Valued Logic in DAV:
      basicsearch".

   September 14, 2004  Fix inconsistent DTD in section 5.2 and 5.4 for
      scope element.

   September 30, 2004  Rewrite editorial note and abstract.  Update
      references (remove unneeded XMLNS, update ref to ACL and BIND
      specs).







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C.10.  since draft-reschke-webdav-search-07

   October 01, 2004  Fix previous section heading (no change tracking).

   October 13, 2004  Fix DTD entry for is-collection.

   November 1, 2004  Fix DTD fragment query-schema-discovery.

   December 11, 2004  Update BIND reference.

   January 01, 2005  Fix DASL and DASLREQ references.

   February 06, 2005  Update XS2 reference.

   February 11, 2005  Rewrite "like" and "DASL" (response header)
      grammar in ABNF.

   May 5, 2005  Update references.  Close issue "abnf" (only use ABNF
      when applicable).

C.11.  since draft-reschke-webdav-search-08

   May 06, 2005  Fix document title.

   September 25, 2005  Update BIND reference.

   October 05, 2005  Update RFC4234 reference.

   October 22, 2005  Author's address update.

   February 12, 2006  Update BIND reference.

   March 16, 2006  Add typed literals to QSD.

   August 20, 2006  Update XML reference.

   August 28, 2006  Add issues "5.3-select-count" (open) and "5.4-
      clarify-depth" (resolved).  Update BIND reference (again).

C.12.  since draft-reschke-webdav-search-09

   December 1, 2006  Fix ABNF for DASL header.

   December 16, 2006  Close issue "qsd-optional", leave QSD optional.
      Close issue "2.4-multiple-uris", suggesting that servers should
      only return one response element per resource in case of multiple
      bindings.  Add and resolve issues "authentication" and "cleanup-
      iana" (adding the header registration for "DASL").  Re-write



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      rational for using the DAV: namespace, although this is a non-WG
      submission.

   January 4, 2007  Close issue "JW16b/JW24a", being related to
      "language-comparison".  Add Appendix B.  Close issues "language-
      comparison", "5_media_type_match", "5.1-name-filtering" and "5.3-
      select-count" as "won't fix", and add appendices accordingly.

   January 24, 2007  Update BIND reference.  Close issue "5.4.2-scope-
      vs-redirects".  Close issue "typed-literal": specify in terms of
      the XPATH 2.9 casting mechanism.  Close issue "1.3-apply-
      condition-code-terminology" (no changes).

C.13.  since draft-reschke-webdav-search-10

   January 29, 2007  Issue "result-truncation": Add appendix describing
      the open issue of Result Paging.  Describe the mechanism of
      marshalling truncated results in a new normative subsection (leave
      the actual example where it was).  Add and resolve issues
      "rfc2606-compliance" and "response-format".  Update contact
      information for Alan Babich, Jim Davis and Surendra Reddy (no
      change tracking).

   February 8, 2007  Update BIND reference.

C.14.  since draft-reschke-webdav-search-11

   Update: draft-newman-i18n-comparator-14 is RFC4790.  Update: RFC2518
   replaced by draft-ietf-webdav-rfc2518bis.  Updated BIND reference.
   Minor tweaks to intro (document organization and relation to DASL).

C.15.  since draft-reschke-webdav-search-12

   Update: draft-ietf-webdav-rfc2518bis replaced by RFC4918.  Updated
   BIND reference.

C.16.  since draft-reschke-webdav-search-13

   Open and close issue "qsd-req-validity".  Updated BIND reference.

C.17.  since draft-reschke-webdav-search-14

   RFC4234 obsoleted by RFC5234.

   Add and resolve issues "5.19.8-opdesc-vs-contains" and "dtd".

   Add clarifications about the behaviour when literal values are not
   compatible with the type of a comparison.



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C.18.  since draft-reschke-webdav-search-15

   Minor editorial improvements.

   Fix description of DAV:scope/DAV:href to use proper URI terminology,
   add reference to RFC 3986.

   Clarify list nature of DASL header.

   Clarify that the DAV:like pattern ABNF is defined in terms of Unicode
   code points.

   Update to UNICODE5.

   Aim for standards track (affects introduction to Appendix B).  Thus,
   make the dependency on [RFC4437] clearly optional, and make the
   reference informative.  Also, mention BCP 47 as candidate for future
   changes to language matching.

   Mention definition of additional condition codes as candidate for
   future changes.

   Consider DAV:contains in Security Considerations.

   Update Surendra's and Alan's contact information.

   Mention search scope discovery as future extensions.  Add a SHOULD
   level requirement for DAV:basicsearch search arbiters to support
   their own URI as search scope.


Appendix D.  Resolved issues (to be removed by RFC Editor before
             publication)

   Issues that were either rejected or resolved in this version of this
   document.

D.1.  standardstrack

   Type: change

   julian.reschke@greenbytes.de (2008-06-27): Umbrella issue for changes
   making this a candidate for the Standards Track.

D.2.  acls

   Type: edit




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   julian.reschke@greenbytes.de (2008-06-29): Clarify security
   considerations with respect to access rights.

D.3.  scope-discovery

   Type: change

   julian.reschke@greenbytes.de (2008-07-02): State that there's no way
   to discover supported scopes, but also add a SHOULD requirement for a
   scope to be supported by DAV:basicsearch.

D.4.  3.2-listsyntax

   In Section 3.2:

   Type: edit

   julian.reschke@greenbytes.de (2008-06-25): Clarify what HTTP-style
   list syntax in headers means; adjust examples.

   Resolution: Done.


Appendix E.  Open issues (to be removed by RFC Editor prior to
             publication)

E.1.  edit

   Type: edit

   julian.reschke@greenbytes.de (2004-07-05): Umbrella issue for
   editorial fixes/enhancements.


Index

   C
      caseless attribute  28-29, 36
      Condition Names
         DAV:search-grammar-discovery-supported (pre)  10
         DAV:search-grammar-supported (pre)  10
         DAV:search-multiple-scope-supported (pre)  10
         DAV:search-scope-valid (pre)  11
      Criteria  6

   D
      DAV:and  28
      DAV:ascending  28



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      DAV:contains  33
      DAV:depth  25
      DAV:descending  28
      DAV:eq  29
         caseless attribute  29
      DAV:from  25
      DAV:gt  29
      DAV:gte  29
      DAV:include-versions  25
      DAV:is-collection  31
      DAV:is-defined  32
      DAV:language-defined  31
      DAV:language-matches  31
      DAV:like  32
      DAV:limit  35
      DAV:literal  29
      DAV:lt  29
      DAV:lte  29
      DAV:not  28
      DAV:nresults  35
      DAV:or  28
      DAV:orderby  28
      DAV:scope  25
      DAV:score  34
         relationship to DAV:orderby  35
      DAV:search-grammar-discovery-supported precondition  10
      DAV:search-grammar-supported precondition  10
      DAV:search-multiple-scope-supported precondition  10
      DAV:search-scope-valid precondition  11
      DAV:select  25
      DAV:supported-query-grammar-set property  16
      DAV:typed-literal  29
      DAV:where  26

   M
      Methods
         SEARCH  9

   O
      OPTIONS method  15
         DASL response header  16

   P
      Properties
         DAV:supported-query-grammar-set  16

   Q
      Query  6



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      Query Grammar  7
      Query Grammar Discovery  15
         using live property  16
         using OPTIONS  15
      Query Schema  7

   R
      Result  7
      Result Record  7
      Result Record Definition  7
      Result Set  7
      Result Set Truncation
         Example  11

   S
      Scope  7
      Search Arbiter  7
      SEARCH method  9
      Search Modifier  7
      Sort Specification  8


Authors' Addresses

   Julian F. Reschke (editor)
   greenbytes GmbH
   Hafenweg 16
   Muenster, NW  48155
   Germany

   Phone: +49 251 2807760
   Email: julian.reschke@greenbytes.de
   URI:   http://greenbytes.de/tech/webdav/


   Surendra Reddy
   Mitrix, Inc.
   303 Twin Dolphin Drive, Suite 600-37
   Redwood City, CA  94065
   U.S.A.

   Phone: +1 408 500 1135
   Email: Surendra.Reddy@mitrix.com








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   Jim Davis
   27 Borden Street
   Toronto, Ontario  M5S 2M8
   Canada

   Phone: +1 416 929 5854
   Email: jrd3@alum.mit.edu
   URI:   http://www.econetwork.net/~jdavis


   Alan Babich
   IBM Corporation
   3565 Harbor Blvd.
   Costa Mesa, CA  92626
   U.S.A.

   Phone: +1 714 327 3403
   Email: ababich@us.ibm.com

































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