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WebDAV Working Group                Alex Hopmann, Microsoft Corporation
Internet Draft                      Lisa Lippert, Microsoft Corporation
Document: draft-hopmann-collection-props-00.txt              Dec, 1998

                  Additional WebDAV Collection Properties


Status of this Memo

   This document is an Internet-Draft.  Internet-Drafts are working
   documents of the Internet Engineering Task Force (IETF), its areas,
   and its working groups.  Note that other groups may also distribute
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Abstract

   The WebDAV protocol defines a basic set of properties that should be
   understood by all DAV servers. This document defines a small set of
   additional properties that are very useful for displaying navigation
   interfaces for WebDAV enabled web sites.

Table of Contents

1.   Introduction .....................................................2
1.1.      Notational Conventions ......................................2
2.   The Collection Properties ........................................2
1.2.      The childcount Property .....................................2
1.3.      The defaultdocument Property ................................3
1.4.      The id Property .............................................3
1.5.      The iscollection Property ...................................3
1.6.      The ishidden Property .......................................4
1.7.      The isstructureddocument Property ...........................4
1.8.      The hassubs Property ........................................5
1.9.      The nosubs Property .........................................5
1.10.       The objectcount property ..................................6
1.11.       The reserved Property .....................................6
1.12.       The visiblecount Property .................................6
3.   Security Considerations ..........................................6
4.   References .......................................................7
5.   Author's Addresses ...............................................7



1.   Introduction

   Collections are a type of resource supported by DAV that may have
   special properties.  The DAV draft [DAV] defines how to interact
   with collections using methods such as MKCOL and PROPFIND, and
   defines a number of properties which were essential to the proper
   use of collections.

   The properties in this draft are not as essential to using
   collections, therefore they are optional.  However, the authors find
   these to be useful properties to clients, especially to save time
   and processing and to know how to display collections.

   Many of these properties are merely hints to a client user interface
   to help it display collections and options on collections in a
   manner that is most helpful to the user.

1.1. Notational Conventions

   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 RFC 2119 [KEYWORDS].

2.   The Collection Properties

   This document defines an additional set of properties for use by the
   WebDAV [1] protocol. These properties provide hints that make it
   easier to provide efficient user interfaces that provide navigation
   for WebDAV enabled web sites.

   If this set of properties is supported, then ALL the properties
   listed in this draft MUST be supported.

   This document follows the same collections as the WebDAV protocol
   specification [1] for defining these properties.

1.2. The childcount Property

Name:          childcount
Namespace:     DAV:
Purpose:       Specifies the number of contained resources.
Description:   This property identifies the number of resources
               contained in a given collection. It contains a single
               integer value with the count of contained resources.
               This property includes child collections in the count.
Definition:    <!ELEMENT childcount (#PCDATA) >

1.3. The defaultdocument Property

Name:          defaultdocument
Namespace:     DAV:
Purpose:       Specifies the default document for a collection.
Description:   This property contains a URL that identifies the default
               document for a collection.  This is intended for
               collection owners to be able to set a default document,
               for example index.html or default.html.  If this
               property is absent, other means must be found to
               determine the default document.
               If this property is present but null, the collection
               does not have a default document and the collection
               member listing should be used (or nothing).
Notes:         The server implementation does not need to store this
               property in the normal property store (the property
               could well be live).

   <!ELEMENT defaultdocument (#PCDATA) >

1.4. The id Property

Name:          id
Namespace:     DAV:
Purpose:       Specifies a unique identifier for this resource.
Description:   This property contains a globally unique string that
               identifies this resource.  This property MUST be unique
               across the entire Internet.  The id property does not
               change if the resource changes.  This property is
               intended to aid in recognition of a resource even when
               moved, updated or renamed.  The value of this property
               is a URI.  The URI could contain a string UUID as
               defined by ISO for RPC [RPC] but any unique URI is
               sufficient.
Definition:    <!ELEMENT id (#PCDATA) >

1.5. The isfolder Property

Name:          isfolder
Namespace:     DAV:
Purpose:       Specifies whether or not a collection should appear as a
               folder.
Description:   This property identifies whether or not a collection
               should appear as a folder. It contains either the values
               "1" or "0".  If "1" or absent, the collection should be
               displayed as a folder.  If "0", the collection should
               NOT be displayed as a folder.  For example, a structured
               document (see below) should have "isfolder" set to "0".
Definition:    <!ELEMENT ishidden (#PCDATA) >

1.6. The ishidden Property

Name:          ishidden
Namespace:     DAV:
Purpose:       Specifies whether or not a resource is hidden.
Description:   This property identifies whether or not a resource is
               hidden. It contains either the values "1" or "0". This
               can be considered a hint to the client UI: under normal
               conditions, for non-expert users, hidden files should
               not be exposed to users.  The server may omit the hidden
               resource from some presentational listings, otherwise
               the client is responsible for removing hidden resources
               when displaying to the user.  If this property is
               absent, the collection is not hidden. Since this
               property provides no actual form of protection to the
               resources, this MUST NOT be used as a form of access
               control and should only be used for presentation
               purposes.
Usage example: Many file systems have the option to hide files from the
               user, but the user can, with special commands, override
               the hiding.
Definition:    <!ELEMENT ishidden (#PCDATA) >

1.7. The isstructureddocument Property

Name:          isstructureddocument
Namespace:     DAV:
Purpose:       Specifies whether the resource is a structured document.
Description:   A structured document is a collection (iscollection
               should also be true), so COPY, MOVE and DELETE work as
               for a collection.  The structured document may behave at
               times like a document.  For example, clients may wish to
               display the resource as a document rather than as a
               collection. This contains either "1" (true) or "0".  If
               this property is absent, the collection is not a
               structured document.
               This property can also be considered a hint for the
               client UI: if the value of "isstructureddocument" is
               "1", then the client UI may display this to the user as
               if it were single document.  This can be very useful
               when the default document of a collection is an HTML
               page with a bunch of images which are the other
               resources in the collection:  only the default document
               is intended to be viewed as a document, so the entire
               structure can appear as one document.
               A Structured document may contain collections.  A
               structured document must have a default document (if the
               "defaultdocument" property is absent, the default
               document is assumed by the client to be index.html).   Definition:    <!ELEMENT isstructureddocument (#PCDATA) >

1.8. The hassubs Property

Name:          hassubs
Namespace:     DAV:
Purpose:       Identifies whether this collection contains any
               collections which are folders (see "isfolder").
Description:   This property identifies whether or not a folder
               contains sub-folders, from the point of view of client
               display. Sub-folders are child collections for which
               "isfolder" = "1".
               The "hassubs" property contains either the values "1"
               (yes) or "0" (zero=no).  If absent, nothing can be
               guessed about whether the collection has sub-folders.
               This property is useful for the efficient display of
               hierarchy user interfaces.
               If "hassubs" = "1", then "isfolder" should also be "1"
               so that clients understand that the folder can be
               expanded to view its children.
Definition:    <!ELEMENT hassubs (#PCDATA) >

1.9. The nosubs Property

Name:          nosubs
Namespace:     DAV:
Purpose:       Identifies whether this collection allows child
               collections to be created.
Description:   This property identifies whether or not a collection
               allows child collections to be created. It contains
               either the values "1" or "0" ("1" indicates that the
               collection does not allow child collections). While this
               data is redundant with that returned by the OPTIONS
               method, providing this information as a property allows
               better performance since the client can verify the
               behavior ahead of time without having to issue an
               individual OPTIONS request on every collection it
               encounters.  If absent, nothing can be guessed about
               whether the collection allows sub-collections.
               This property can also be considered to be a hint to the
               UI about displaying options to the user (the UI might
               eliminate the option to create a child collection).   It
               is different from a "create child" access right, because
               the client UI may want to display a "create child
               collection" option without trying to find out if the
               user has permissions.  This property can be used to
               suggest that creating child collections just doesn't
               make sense on this collection no matter what rights the
               user has.  It is most useful on special-purpose
               collections, such as a deleted files collection or a
               collection which represents a device such as a printer.
               This property should not be construed as meaning that
               sub-collections do not already exist on the collection -
               it simply prevents new collections from being created by
               the client.
Definition:    <!ELEMENT nosubs (#PCDATA) >

1.10.      The objectcount property

Name:          objectcount
Namespace:     DAV:
Purpose:       To count the number of non-folder resources in the
               collection.
Description:   This is different from childcount in that it omits
               counting child collections for which "isfolder" = "1".
Definition:    <!ELEMENT objectcount (#PCDATA) >

1.11.      The reserved Property

Name:          reserved
Namespace:     DAV:
Purpose:       Specifies whether or not the collection is reserved.
Description:   A reserved collection is one that is specially managed
               by the server and cannot be deleted, renamed, or moved
               by the client. It contains either the values "1" or "0".
               Attempts to MOVE or DELETE a reserved collection will
               fail, and this SHOULD be reflected in the client UI.  If
               absent, the collection should NOT be reserved.  The
               server may allow clients to set this property.
               It may make sense to also specify that this collection
               is reserved in the resourcetype; however, in most ways
               this behaves like a normal collection.
Definition:    <!ELEMENT reserved (#PCDATA) >

1.12.      The visiblecount Property

Name:          visiblecount
Namespace:     DAV:
Purpose:       Counts the number of visible non-folder resources in the
               collection.
Description:   This is the most immediately useful property for the
               client UI to use to display the sizes of collections for
               users.  The client UI could also display progess when
               downloading a long list of children in a collection if
               it knows the total number in advance.  This counts all
               children for which "ishidden" = "0" and "isfolder" =
               "0".
Definition:    <!ELEMENT reserved (#PCDATA) >

3.   Security Considerations

   The ability to hide resources should not be considered a security
   feature.  With the current described behavior, there is a danger
   that users will be able to discover the hidden resource by trying to
   write a file of the same name as the hidden resource. In addition,
   since hidden resources will be exposed via PROPFIND, there is no
   actual security for them, the hidden nature MUST simply be for
   presentation (user interface) purposes. This is because the hidden
   resource feature described here is not intended to be a security
   feature but a client display feature.

   Solving the problem of having resources which are undetectable under
   certain conditions is beyond the scope of this draft.

4.   References

   [HTTP] R. Fielding, J. Gettys, J. C. Mogul, H. Frystyk, and T.
   Berners-Lee, "Hypertext Transfer Protocol -- HTTP/1.1", RFC 2068,
   U.C. Irvine, DEC, MIT/LCS, January 1997.

   [DAV] Y. Goland, E.J. Whitehead, A. Faizi, S.R. Carter, D. Jenson,
   "Extensions for Distributed Authoring on the World Wide Web", April.
   1998, internet-draft, work-in-progress, draft-ietf-webdav-protocol-
   08.

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

   [RPC] ISO/IEC 11578:1996(E) International Standard: "Information
   Technology -- Open Systems Interconnection -- Remote Procedure Call",
   December, 1996 (see Annex A)


5.   Author's Addresses

   Alex Hopmann
   Microsoft Corporation
   One Microsoft Way
   Redmond, WA 98052
   Email: alexhop@micrososft.com

   Lisa Lippert
   Microsoft Corporation
   One Microsoft Way
   Redmond, WA 98052
   Email: lisal@microsoft.com


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