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INTERNET-DRAFT                                      N. Popp
February 8, 2000                             RealNames Inc.
Expires August 8, 2000                          M. Mealling
draft-ietf-cnrp-01.txt              Network Solutions, Inc.
                                                 M. Moseley
                                              Netword, Inc.


                CNRP PROTOCOL SPECIFICATION


1. Status of this memo

This document is an Internet-Draft and is in full conformance
with all provisions of Section 10 of RFC2026.

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 working documents as
Internet-Drafts.

Internet-Drafts are draft documents valid for a maximum of six
months and may be updated, replaced, or obsoleted by other
documents at any time.  It is inappropriate to use Internet-
Drafts as reference material or to cite them other than as
"work in progress."

The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt

The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.

Please send comments on this draft to CNRP-IETF@LISTS.INTERNIC.NET.


2. Abstract
People often refer to things in the real world by a common
name or phrase, e.g., a trade name, company name, or a book
title. These names are sometimes easier for people to
remember  and type than URLs.  Furthermore, because of the
limited syntax of URLs, companies and individuals are
finding that the ones that might be most reasonable for
their resources are being used elsewhere and so are
unavailable.

Services are arising that offer a mapping from common names
to Internet resources (e.g., as identified by a URI). These
services often resolve common name categories such as
company names, trade names, or common keywords. Thus, such a
resolution service may operate in one or a small number of
categories or domains, or may expect the client to limit the
resolution scope to a limited number of categories or
domains. For example, the phrase "Internet Engineering Task
Force" is a common name in the "organization" category, as
is "Moby Dick" in the book category.

Two classes of clients of such services are being built,
browser improvements and web accessible front-end services.
Browser enhancements modify the "open" or "address" field of
a browser so that a common name can be entered instead of a
URL. Internet search sites integrate common name resolution
services as a complement to search. In both cases, these may
be clients of back-end resolution services. In the browser
case, the browser must talk to a service that will resolve
the common name. The search sites are accessed via a
browser. In some cases, the search site may also be the back-
end resolution service, but in others, the search site is a
front-end to a collection of back-end services.

This effort is about the creation of a protocol for client
applications to communicate with common name resolution
services, as exemplified in both the browser enhancement and
search site paradigms. Although the protocol's primary
function is resolution, it is intended to address the issues
of internationalization and privacy as well. Name resolution
services are not generic search services and thus do not
need to provide complex Boolean query, relevance ranking or
similar capabilities. The protocol is a simple, minimal
interoperable core. Mechanisms for extension are provided,
so that additional capabilities can be added.

Several other issues, while of importance to the deployment
of common name resolution services, are outside of the
resolution protocol itself and are not in the initial scope
of the proposed effort. These include discovery and
selection of resolution service providers, administration of
resolution services, name registration, name ownership, and
methods for creating, identifying or insuring unique common
names.

3. Introduction
For the purposes of this document, a "common name" is a word
or a phrase, without imposed syntactic structure, that may
be associated with a resource.  These common names will be
used primarily by humans,  as opposed to machine agents.  A
common name "resolution service" handles these associations
between common names and data (resources, information about
resources, pointers to locations, etc).  A single common
name may be associated with different data records, and more
than one resolution service is expected to exist.  Any
common name may be used in any resolution service.

Common names are not URIs (Uniform Resource Identifiers) in
that they lack the syntactic structure imposed by URIs;
furthermore, unlike URNs, there is no requirement of
uniqueness or persistence of the association between a
common name and a resource.  (Note:  common names may be
expressed in a URI, the syntax for which is described
herein.)

This document will define a protocol for the parameterized
resolution necessary to make common names useful.
"Resolution" is defined as the retrieval of data associated
(a priori) with descriptors that match the input request.
"Parameterized" means the ability to have a multi-component
descriptor.  Descriptors are not required to provide unique
identification, therefore 0 or more records may be returned
to meet a specific input query.

4. Basic object model
The protocol will consist of a simple request /response
mechanism.  There will be two types of queries.

  1. A `special' initial query that establishes the schema
     for a particular CNRP database and communicates that to the
     client.  The CNRP client will send this query, and in turn
     receive an XML document defining the query properties that
     the database supports.  (In CNRP, XML is used to define and
     express all objects.)

  2. A `standard' query, which is the submission of the CNRP
     search string to the database.  The query will conform to
     the previously established schema.

There will be a set of query properties, listed below,
treated as hints by the server.  Note:  a CNRP database will
accept any correctly encoded CNRP query property; the extent
to which a query result is responsive to those properties is
a service differentiator.  The base properties that are
always supported are common name, language, geography,
category, and range (start and length of the result set).
CNRP allows database service providers to create unique data
types and surface them to any CNRP client via the CNRP
schema XML documents.

Note:  the descriptive portions of this document contain
pieces of XML code that are *illustrative examples only*.
Section 6 of this document contains the XML DTD for CNRP,
which is definitive.

4.1  Hints
A hint is an assertion by the user about him or her self and
the context in which he/she is operating.  There is no data
type `hint'; a hint is expressed within the structure of the
query itself and is limited or enabled by the richness of
the defined query namespace.  In effect, a query and any
property within it is a hint.

An example of this would be the required property
"language", in which a query might be created that specifies
the primary language in which you want to see results, the
secondary language, and so on.  So seeing results in US
English followed by European French and South American
Spanish would be:

<property name="language" type="iso646">en-US</property>
<property name="language" type="iso646">fr-FR</property>
<property name="language" type="iso646">sp-MX</property>


The fact that a hint exists does not mean that a CNRP
database must respond to it.  This best-effort approach is
similar to relevance ranking in a search engine (high
precision, low recall); hints are similar to a search
engine's selection criteria. CNRP services will attempt to
return the results "closest" to the selection criteria.
This is quite different from a SQL database approach where a
SQL query returns the entire results set and each result in
the set must match all the requirements expressed by the
qualifier (the SQL WHERE clause).

4.2  Transport independence
This document defines CNRP in terms of an object model, the
encoding scheme used to express it (XML documents), and
response/request interaction model.  Therefore it is
transport-independent.  It is expected that the primary
transport used for CNRP will be HTTP, but that is certainly
not a requirement.  Most  aspects of authentication and
security are a requirement of the transport and not of CNRP.
The protocol does not, in and of itself, support any
authentication and security.

Discovery of the transport associated with a CNRP database
is accomplished through DNS.  The syntax for a CNRP URI is:

  CNRP:<[host]>:<[port]>/path/<common name>;paraname=value,
  paraname=value,...

"CNRP", in conjunction, with the URI content, denotes a DNS
entry containing a Naming Authority Pointer (NAPTR).  The
NAPTR specifies how a CNRP URI is dynamically rewritten by
the client to adhere to some transport (HTTP, GOPHER, etc.)
Because this rewrite can be a URL, a CNRP URI can thus be
cached and assigned a time-to-live (TTL).

5. Object Model:
5.1 Properties:
5.1.1 Base properties
In CNRP, objects are property lists. A property has a unique
name and type. Some properties can be part of the query or
the results list or both. For simplicity, CNRP is limiting
property values to string values.

CNRP introduces a set of base properties. Among these
properties, CNRP distinguishes between core properties and
optional properties. Core properties are the minimal set of
properties that all CNRP services MUST support. The core
properties define the level of interoperability between CNRP
services. The proposed core properties are:

  1.   CommonName: the common name associated with a resource.
  2.   ID: an opaque string that serves as a unique identifier
       (typically a database ID)
  3.   URI: An URI as define by RFC-2026.

In addition to core properties, CNRP introduces optional
properties to enable a wider range of  CNRP based services.
Although, these properties are not required, it is expected
that many services, especially large one, will implement
them. An equally important goal for introducing additional
properties is to provide a powerful results filtering
mechanism. This is a requirement for large namespaces that
contain several million of names. The optional properties
are:

  1.   Language: The language of a resource associated with a
       resource.
  2.   Geography: The geographical region or location
       associated with a resource.
  3.   Category: The category associated with a resource.
  4.   Description: A short text abstract associated with a
       resource.
  5.   Range: The range is a results set control property. The
       range property is used to specify the starting point and the
       length of a results set (e.g. I want 5 records starting at
       the 10th record)

The language property is expressed using language values as
defined by ISO-3166.

5.1.2 Multi type properties
The "geography" and "category" properties introduced in the
CNRP model can be expressed using many different value sets.
For example, geography can be specified in terms of a
country code, a postal code or in terms of spatial
coordinates. Therefore, for such properties, CNRP introduces
a "type" attribute. To facilitate interoperability, CNRP
defines the main primitive types as well. Property types can
be extended by a specific service through the definition of
new type values (see extensibility section).

The multi-type properties and the main types are defined
below:


5.1.2.1 Geography:

  1.   type = "freeform" value = a free form expression for a
       geographical location (e.g. "palo alto in california").
  2.   type = "ISO3166-1" value = a geographical region
       expressed using a standard country code as defined by
       ISO3166-1 (e.g. "US").
  3.   type = "ISO3166-2" value = a geographical region
       expressed using a standard region and country codes as
       defined by ISO3166-2 (e.g. "US-CA").type = "latitude-
       longitude-elevation " value = the latitude, longitude and
       elevation of a geographical location.
  4.   type = "GPS" value = a geographical location expressed
       using the standard GPS coordinates system (e.g. ???)1
  5.   type = "LLE" value = a geographical location expressed
       using the Latitude-Longitude-Elevation coordinates system
       (e.g. ???2)


5.1.2.2 Category

  1.   type = "freeform" value = a free form expression for a
       category (e.g. "movies").
  2.   type =  "NAICS" value = The North American Industry
       Code System.

       When the "type" is unspecified, the value defaults to
       "freeform". The free form type value is important
       because it allows very simple user interface where the
       user can enter a value in a text field. It is up to the
       serviced to interpret the value correctly and take
       advantage of it to increase the relevance of results
       (using specialized dictionaries for instance).

5.1.2.3   Common name - String encoding and equivalence rules
CNRP specifies that common name strings should be encoded
using UTF-8. CNRP does not specify any string equivalence
rules for matching a common name in the query against a
common name of a Resource. String equivalence rules are
language and service dependant. They are specific to
relevance ranking algorithms, hence treated as CNRP
services. Consequently, string equivalence rules are not
part of the CNRP protocol specification. For example, the
query member:

        <commonname>bmw</commonname>

Should be read as a selection criterion for a resource with
a common name LIKE (similar to) the string "bmw" where the
exact  definition of the LIKE operator is intuitive, yet
specific to the queried CNRP service.

5.2  Objects:
5.2.1     Query:
The Query object encapsulates all the query properties such
as CommonName, ID, language, geography, category, and range.
A Query cannot be empty. A Query must contain either a
common name, or an ID. A Query can also contain the custom
properties defined  by a specific CNRP service.

For example, a query for the first 5 resources whose common
name is like "bmw" would be expressed as:

<query>
        <commonname>bmw</commonname>
        <range start="1" length="5"/>
</query>

5.2.1.1 Logical operations within a Query
The Query syntax is extremely simple. CNRP does not
extensively support Boolean logic operator such as OR, AND
or NOT. However, there exist two implicit logical operations
that can be expressed through the Query object and its
properties. First, a query with multiple property-value
pairs implicitly expresses an AND operation on the query
terms. For instance, the CNRP query to request all the
resources whose common name is like "bmw", AND whose
language is "German" can be expressed as:

<query>
     <commonname>bmw</commonname>
     <property name="language" type="iso646">de-DE</property>
</query>

Note however, that because the server is only trying to best
match the Query criteria, there is no guarantee that all or
any of the resources in the results match both requirements.

In addition, for enumerated value types only (e.g.
language), CNRP allows the client to express a logical OR by
specifying multiple values for the same property within the
Query. For example, the logical expression:

property = value1 OR property = value2 .OR property = valueN

Will be expressed as:

<property>value1</property>
<property>value2</property>
<property>valueN</property>

It is important to underline that this form is only
applicable to enumerated types. In particular,  logical OR
operations on the common name are not supported. Note that
the ordering or the property-value pairs in the query
implies a precedence. As a consequence, CNRP also introduces
one special string value: "*". Not surprisingly, "*" means
all admissible values for the typed property. For example,
the following query requests all the resources whose common
name is like BMW and whose language is preferably in German
or French or any other language.

<query>
     <commonname>bmw</commonname>
     <property name="language" type="iso646">de-DE</property>
     <property name="language" type="iso646">fr-FR</property>
     <property name="language" type="iso646">*</property>
</query>


5.2.1.2 Direct and indirect property values in the Query:
An important concept is that in a query, a CNRP property can
carry two different types of values: an indirect and a
direct value.

The indirect value corresponds to an implicit configuration-
like setting. Indirect values will typically be derived from
a user's global preferences, general client settings or any
other source of user profile information. For example, a
language preference set to French for browsing would
translate into:

<property name="language" type="iso646" source="indirect">
        fr-FR</property>

Another important source for indirect values is the physical
"entry point" for that specific query, that is, the context
surrounding the environment where the query has been
entered. For example, if  a CNRP query has been entered on a
German Web site, there is a strong (yet implicit) assumption
that the user is predominantly looking for resources in the
German language.

The direct value on the other hand, corresponds to the local
value specified by the CNRP user for a specific query (In
this CNRP query, I am looking for Web pages with the common
name "fettuccini" that are in the Italian language.although
my default language is set to French.). Distinguishing
between indirect and direct query properties is extremely
important for a CNRP server in order to generate the most
relevant list of results. To differentiate a direct value
from an indirect value, CNRP uses a "source" property
attribute:

source = "indirect" | "direct"

Because, they have different precedence, it is important for
a CNRP resolution service to be able to distinguish between
the two types of information sources. When unspecified, the
source is assumed to be "direct" (default value of the
source attribute).

For instance, in a wireless device, the device location
(geography) can be determined accurately. The wireless CNRP
client may decide to pass the device current location as an
indirect specification of the desired geography for the
resource. For example, if the user is looking for resources
with common name "Starbucks", the device could pass the
following information to the client:

<geography type="GPS" source="indirect">345,455,3555</geography>

At the same time, the same user intending to travel to
Montreal may want to explicitly specify in the query that he
is actually looking for a Starbucks in Montreal. In such
case the query would contain the following information:

<geography type="freeform" source="direct">Montreal</geography>
<geography type="GPS" source="indirect">345,455,3555</geography>

5.3 Results:
The results object is a container for CNRP results. The type
of objects contained in Results can be: Resource, Service,
Error, Referral and Schema.

5.3.1 Resource
A Resource object describes a resource (e.g. a Web page, a
person, an object identified by a URI). The Resource object
can contain the commonname, URI, ID, description, language,
geography, and category of the resource. A Resource can also
be augmented using custom properties. Lastly, a Resource can
also reference a service object to indicate its origin.

<results>
     <resource>
          <commonname>bmw</commonname>
          <property name="language" type="iso646">de-DE</property>
          <property name="category" type="freeform">
             carcompanies</property>
          <property name="geography" type="ISO3166-1">DE</property>
          <id>foo.com:234364</id>
          <resourceuri>http://www.bmw.de</resourceuri>
          <description>Wunderbar BMWs!</description>
          <serviceRef ref="0" />
     </resource>
</results>

5.3.2 Service
The Service object provides an encapsulation of an instance
of a CNRP service. A service is uniquely identified through
the ServiceURI property. Services can also include a
description, a brief textual description of the service.

<service>
     <serviceuri>http://cnrp.foo.com</serviceuri>
     <description>foo.com is a CNRP service specialized on cocktail
        recipes</description>
</service>

The service object can also be extended by including
existing properties to further describe the service. For
instance, a service that focuses on French companies could
be expressed as:

<service>
     <serviceuri>http://cnrp.foo.com</serviceuri>
     <property name="category" type="freeform">companies</property>
     <property name="geography" type="ISO3166-1">FR</property>
</service>

The service object  also encapsulates a list of server
objects. The server object is used to describe a CNRP server
(or a cluster of servers). A server is identified through
its serverURI. A server can be further described using
existing properties. For example, the following example
defines two clusters of  CNRP servers one in the US and one
in France.

<service>
     <serviceuri>http://cnrp.foo.com</serviceuri>
     <servers>
          <server>
               <serverURI>http://router.us.widgetco.com:4321/foo?
                     </serverURI>
               <property name="geography" type="ISO3166-
          1">US</property>
          </server>
          <server>
               <serverURI>http://router.fr.realnames.com:4321/foo?
                  </serverURI>
               <property name="geography" type="ISO3166-
          1">FR</property>
          </server>
     </servers>
</service>

5.3.3 Error
An Error object indicates an error in the results set. The error object
encapsulates two properties: an error number and an error description.

<results>
     <error>
          <number>345</number>
          <description>The CNRP foo.com database is temporarily
     unreachable</description>
     </error>
</results>

5.3.4 Referral
A Referral object in the results set is a place holder for
un-fetched results from a different service. Referrals
typically occur when a CNRP server knows of another service
capable of providing relevant results for the query and
wants to notify the client about this possibility. The
client can decide whether it wants to follow the referral
and resolve the extra results by contacting the referred-to
service using the information contained within the Referral
object (a Service object). The Referral is a simple
mechanism to enable hierarchical resolution as well as to
join multiple resolution services together.

<results>
     <service id="0">
          <serviceuri>http://cnrp.bar.com/</serviceuri>
     </service>
     <resource>
          <commonname>bmw</commonname>
          <property name="language" type="iso646">de-DE</property>
          <id>foo.com:234364</id>
          <resourceuri>http://www.bmw.de/</resourceuri>
     </resource>
     <referral>
          <serviceref ref="0" />
     </referral>
</results>

5.3.5 ServiceQuery & schema:
A subclass of Query, the ServiceQuery object supports the
dynamic discovery of a specific CNRP service's
characteristics. To give a full description of a CNRP
service, the response to a ServiceQuery returns the Service
object described in section 5.3.2 with the following schema
information.

  1.   The new Properties introduced by the CNRP service
       (Property schema),
  2.   The properties used to describe the Service object
       (Service schema)
  3.   The properties that belong to the query interface
       (Query schema)
  4.   The properties that belong to a resource within the
       results (Resource schema).

These leads to the following new objects definitions:

  *    PropertySchema -- A property schema describes all the
       custom properties introduced by the service.
  *    PropertyDefinition -- A property definition describes a
       custom property. A property definition has a name and a type
       (the name and the type of the property).
  *    ProperyReference -- A property reference is a reference
       to a property definition so that it can be included within a
       given schema (a service, query or resource schema).
  *    ServiceSchema -- The service schema defines the
       properties used to describe the service.
  *    QuerySchema -- A query schema describes the structure
       of a query handled by the CNRP service.
  *    ResourceSchema -- A resource schema describes the
       resource returned as a result by the CNRP service.

For example, a CNRP query to discover a service's capabilities will
be in the form:

<serviceQuery/>

And for a CNRP service for cocktail recipes in French, the
corresponding response would be:

<service>
     <propertySchema id="1">
          <propertyName>cocktailrecipe</propertyName>
          <propertyType>freeform<propertyType>
     </propertySchema>
     <querySchema>
          <propertyReference
          required="yes">language</propertyReference>
     </querySchema>
     <resourceSchema>
          <propertyReference required="no" idref="1"/>
     </resourceSchema>
</service>

6. XML DTD for CNRP
<!-- The document tag -->
<!ELEMENT cnrp (query|results|ServiceQuery)>


<!-- Used to request a Service object -->
<!ELEMENT ServiceQuery EMPTY>


<!-- A query can either request a schema, a specific record by id,  -->
<!-- or a common-name with a set of properties (or assertions) about-->
<!-- the entity doing the query.                                    -->
<!ELEMENT query (id|(commonName,property*))>
<!ELEMENT id (#PCDATA)>


<!ELEMENT commonName (#PCDATA)>
<!-- NOTE: CNRP defines several well known properties and types.     -->
<!-- See Appendix A for details.                                     -->
<!ELEMENT property (#PCDATA)>
<!-- The name of the property -->
<!ATTLIST property name CDATA #REQUIRED>
<!-- The type of the property -->
<!ATTLIST property type CDATA "freeform">
<!-- The `source' of the data. This means whether or not it came     -->
<!-- from the entity doing the request or from some other default    -->
<!-- source. This could also be considered a rudimentary weighting   -->
<!-- mechanism.                                                      -->
<!ATTLIST property source (direct|indirect) "direct">


<!--
     A result can contain this:
     ((Service*, Resource*, Referral*, Error*) | Service)
     The problem is that Resources, Referrals and Errors can occur in
     any order and repeat any number of times.  Since we can't
     specify a non-ordered list of sub-elements in the definition
     of the results element we have to specify that the Results
     element can contain anything.
-->


<!ELEMENT results ANY>
<!ELEMENT Resource (commonName,id,resourceURI,
    serviceRef,
    description,
    property*)>


<!-- The entire point of all this... -->
<!ELEMENT resourceURI (#PCDATA)>
<!ELEMENT description (#PCDATA)>


<!ELEMENT referral (serviceRef)>


<!ELEMENT error (#PCDATA)>
<!ATTLIST error code CDATA #REQUIRED>


<!-- serviceRef is used to point to one of a set of provided service -->
<!-- objects. This is so that a resource can point to which service  -->
<!-- it came from. We could include the entire service object but    -->
<!-- then we would be repeating large amounts of information.        -->
<!ELEMENT serviceRef EMPTY>
<!-- This specifies if a property is required as part of the query.  -->
<!ATTLIST serviceRef ref IDREF #IMPLIED>


<!ELEMENT service (ServiceURI,
   Servers+,
   description+,
   property*,PropertySchema+,QuerySchema+,ResourceSchema+,
   ServiceSchema+)>
<!-- The time to live of the schema in seconds since it was retrieved -->
<!ATTLIST service ttl CDATA "0">
<!ATTLIST service id ID #IMPLIED>
<!ELEMENT ServiceURI (#PCDATA)>
<!ELEMENT Servers (Server+)>
<!ELEMENT Server (ServerURI, property*)>
<!ELEMENT ServerURI (#PCDATA)>


<!ELEMENT PropertySchema (PropertyDefinition*)>
<!ELEMENT PropertyDefinition (PropertyName, PropertyType*)>
<!ATTLIST PropertyDefinition id ID #IMPLIED>


<!ELEMENT PropertyName (#PCDATA)>
<!ELEMENT PropertyType (#PCDATA)>
<!-- This specifies if the type is meant to be the default type. -->
<!-- This is usually reserved for "freeform".                    -->
<!ATTLIST PropertyType default (no|yes) "no">


<!-- The properties you can use in a query -->
<!ELEMENT QuerySchema (PropertyReference*)>


<!-- The properties you can expect to see in an Resource -->
<!ELEMENT ResourceSchema (PropertyReference*)>


<!-- The properties you can expect to find in a Service definition -->
<!ELEMENT ServiceSchema (PropertyReference*)>


<!ELEMENT PropertyReference (#PCDATA)>
<!-- This specifies if a property is required as part of the query. -->
<!ATTLIST PropertyReference ref IDREF #IMPLIED>
<!ATTLIST PropertyReference required (no|yes) "no">


6.1 Examples
6.2 Service Description Request
This is what the client sends when it is requesting a
servers schema.


<?xml version="1.0"?>
<!DOCTYPE cnrp SYSTEM "CNRPDTD.xml">
<cnrp>
     <ServiceQuery />
</cnrp>


This is the result. Notice how the Service tag is used to allow the
service to describe itself in its own terms.


<?xml version="1.0"?>
<!DOCTYPE cnrp SYSTEM
"D:\WINNT\Profiles\Administrator\Desktop\CNRPDTD.xml">
<cnrp>
     <results>
     <service ttl="43200">
          <serviceURI>urn:foo:bar</serviceURI>
          <servers>
          <server>
          <serverURI>http://host1.acmecorp.com:4321/foo?</serverURI>
          <priority>1</priority>
               </server>
               <server>
          <serverURI>smtp://host2.acmecorp.com:4321/foo?</serverURI>
          <priority>1</priority>
               </server>
          </servers>
          <description>This is the AcmeCorp CNRP Service</description>
          <!-- This property means that AcmeCorp specializes in
tradename
     services -->
          <property name="category" type="naics">544554</property>
          <property name="BannerAdServer"
type="uri">http://adserver.acmecorp.com/</property>
          <propertySchema>
               <propertyDefinition id="1">
                    <propertyName>workgroupID</propertyName>
                    <propertyType default="yes">freeform</propertyType>
                    <propertyType
               default="no">domainname</propertyType>
                    </propertyDefinition>
                    <propertyDefinition id="2">
                    <propertyName>BannerAdServer</propertyName>
                    <propertyType default="yes">URI</propertyType>
               </propertyDefinition>
          </propertySchema>
          <querySchema>
               <propertyReference ref="1" required="yes" />
          </querySchema>
          <resourceSchema>
               <propertyReference ref="1" required="yes" />
          </resourceSchema>
          <serviceSchema>
               <propertyReference ref="2" required="yes" />
          </serviceSchema>
     </service>
     </results>
</cnrp>


6.3 Sending A Query and Getting A Response

This is the query that is sent from the client to the
server:

<?xml version="1.0"?>
<!DOCTYPE cnrp SYSTEM
"D:\WINNT\Profiles\Administrator\Desktop\CNRPDTD.xml">
<cnrp>
 <query>
    <commonName>Fido</commonName>
    <property name="geography" type="iso3166-2" source="default">
       CA-QC</property>
    <property name="geography" type="iso3166-1"
source="explicit">CA</property>
    <property name="language" type="iso646">fr-CA</property>
 </query>
</cnrp>


This is the result set. It is sent back in response to the
query. This result set includes a referral and a non-fatal
error.

<?xml version="1.0"?>
<!DOCTYPE cnrp SYSTEM
"D:\WINNT\Profiles\Administrator\Desktop\CNRPDTD.xml">
<cnrp>
     <results>
          <service id="0">
               <serviceURI>http://acmecorp.com</serviceURI>
          </service>
          <service id="1">
               <serviceURI>http://serverfarm.acmecorp.com</serviceURI>
          </service>
          <service id="2">
                <serviceURI>http://servers.acmecorp.co.uk</serviceURI>
          </service>
          <resource>
                    <commonName>Fidonet</commonName>
                    <id>1333459455</id>
                    <resourceUri>http://www.fidonet.ca</resourceUri>
                    <serviceRef ref="0" />
                    <description>This is ye olde Canadian
                       Fidonet</description>
          </resource>
          <resource>
                    <commonName>Fidonet</commonName>
                    <id>1333459455</id>
                    <resourceURI>http://host:port/bla</resourceURI>
                    <serviceRef ref="1" />
          </resource>
          <resource>
                    <referral>
                    <serviceRef id="2" />
               </referral>
          </resource>
     </results>
</cnrp>


6.4  Examples to be done:
6.4.1     Complex Result
6.4.2     No Results
6.4.3     Error Conditions

7. Transport
Two CNRP transport protocols are specified. HTTP is used due
to its popularity and ease of integration with other web
applications. SMTP is also used as a way to illustrate a
protocol that has a much different range of  latency than
most protocols.

7.1.1 HTTP transport
The HTTP transport is fairly simple. The client connects to
an HTTP based CNRP server and issues the POST method with
the Content-type and Accept header set to "application/xml".
The content of the POST body is the CNRP XML document that
is being sent.

The results are sent back to the client with a Content-Type
of  "application/xml".  The body of the result is the CNRP
XML document being  sent to the client.

7.1.2 SMTP transport
The SMTP transport is very similar to the HTTP transport.
Since there is no method to specify, the CNRP XML document
is simply sent to a particular SMTP endpoint with its
Content-Type set to "application/xml". The server responds
by sending a response to the originator of the request with
the results in the body and the Content-Type set to
"application/xml".

8. Security Considerations
This is where we talk about the various security threats.
Two that need to be addressed are Man in the Middle attacks
and posing as a service by spoofing a Service object.

The proposed solution for man in the middle attacks is to
utilize transport level authentication and encryption where
available. In the case where the transport can't provide the
level of required authentication, individual entries or the
entire response can be signed/encrypted.

In the case of where a service attempts to pose as another
by spoofing the serviceURI in the Service object, the
Service object should be signed.  A client can then verify
the Service object's veracity by verifying the signature.
How the client obtains that authoritative public key is out
of scope since it depends on the service discovery problem.
8.1  XXX To be done: add additional threat scenarios

9. IANA Considerations
The major consideration for the IANA is that the IANA will
be registering well known properties and property types. It
will not register values.  Since this document does not
discuss CNRP service discovery, the IANA will not be
registering the existence of servers or Server objects.

There are two types of entities the IANA can register:
properties and property types. If a property or type is not
registered with the IANA then they must start with "x-".

The required information for the registration of a new
property is the property's name, its default type, and a
general description. A new type requires the type's name,
what properties it is valid for, and a description.

See Appendix A for some example property and type
registrations.

10. Appendix A: Well Known Property and Type Registration Templates

Property Name: Geography
Default Type: ISO3166-1
Description: A geographic location

Paramater Name: Language
Default Type: RFCXXXX3
Description: A language specification

Property Name: Category
Default Type: freeform
Description: A node in some system of semantic relationships that is
considered relevant to the common-name.

Property Name: Range
Default Type: range
Description: A range given in the format "x,y" where x is the starting
point and y is the length. This property is used by the client to tell
the server that is is requesting a subrange of the results.

Types:

Type: freeform
Property: ALL
Description: The value is to be interpreted by the server the best way
it knows how. This value has no defined structure.

Type: ISO3166-2
Property: Geography
Description: The combination of country and sub-region codes.

Type: ISO3166-1
Property: Geography
Description: Country Codes

Type: POSTALCODE
Property: Geography
Description: A postal code that is valid for some region. A good
example is the Zip code system used in the US.

Type: GPS
Property: Geography
Description: A code in the format used by the Global Positioning System.

Type: ISO636
Property: Language
Description: language codes

Type: NAICS
Property: Category
Description: North American Industry Code System

11.   Author contact information

Nico Popp
RealNames Corporation
2 Circle Star Way, 2nd Floor
San Carlos, CA  94070-1350

Phone: (650) 298 8080
Email: nico@realnames.com

Michael Mealling
Network Solutions, Inc.
505 Huntmar Park Drive
Herndon, VA 22070

Phone: (703) 742-0400
EMail: michaelm@netsol.com
Marshall Moseley
Netword, Inc.
702 Russell Avenue
Gaithersburg, MD 20877-2606

Phone: (240) 631-1100
Email: marshall@netword.com


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