wdiff draft-ietf-simple-xcap-00.txt draft-ietf-simple-xcap-01.txt

SIMPLE J. Rosenberg
Internet-Draft dynamicsoft
Expires: December 22, 2003 June 23, April 26, 2004 October 27, 2003

The Extensible Markup Language (XML) Configuration Access Protocol
(XCAP)
draft-ietf-simple-xcap-00
draft-ietf-simple-xcap-01

Status of this Memo

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Abstract

This specification defines the Extensible Markup Language (XML)
Configuration Access Protocol (XCAP). XCAP allows a client to read,
write and modify application configuration data, stored in XML format
on a server. XCAP is not a new protocol. XCAP maps XML document
sub-trees and element attributes to HTTP URIs, so that these
components can be directly accessed by HTTP.

Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Overview of Operation . . . . . . . . . . . . . . . . . . . 4
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . 5
4. Application Usages . . . . . . . . . . . . . . . . . . . . . 6
5. URI Construction . . . . . . . . . . . . . . . . . . . . . . 8
5.1 Identifying the XML Document . . . . . . . . . . . . . . . . 8
5.2 Identifying the XML Nodes . . . . . . . . . . . . . . . . . 9
6. Client Operations . . . . . . . . . . . . . . . . . . . . . 10 12
6.1 Creating a New Document . . . . . . . . . . . . . . . . . . 10 12
6.2 Replace an Existing Document . . . . . . . . . . . . . . . . 10 12
6.3 Deleting a Document . . . . . . . . . . . . . . . . . . . . 10 12
6.4 Fetching a Document . . . . . . . . . . . . . . . . . . . . 10 12
6.5 Creating a New Element . . . . . . . . . . . . . . . . . . . 10 12
6.6 Replacing an Element in the Document . . . . . . . . . . . . 11 13
6.7 Delete an Element . . . . . . . . . . . . . . . . . . . . . 12 13
6.8 Fetch an Element . . . . . . . . . . . . . . . . . . . . . . 12 13
6.9 Create an Attribute . . . . . . . . . . . . . . . . . . . . 12 14
6.10 Replacing Attributes . . . . . . . . . . . . . . . . . . . . 13 14
6.11 Deleting Attributes . . . . . . . . . . . . . . . . . . . . 13 14
6.12 Fetching Attributes . . . . . . . . . . . . . . . . . . . . 13 14
6.13 Fetching Metadata . . . . . . . . . . . . . . . . . . . . . 13
6.14 Read/Modify/Write Transactions . . . . . . . . . . . . . . . 14 15
7. Server Behavior . . . . . . . . . . . . . . . . . . . . . . 15 16
7.1 POST Handling . . . . . . . . . . . . . . . . . . . . . . . 16
7.2 PUT Handling . . . . . . . . . . . . . . . . . . . . . . . . 17
7.3 GET Handling . . . . . . . . . . . . . . . . . . . . . . . . 18
7.4 DELETE Handling . . . . . . . . . . . . . . . . . . . . . . 18
7.5 Managing Modification Times Etags . . . . . . . . . . . . . . . . . . . . . . . 19
8. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 21 20
9. Security Considerations . . . . . . . . . . . . . . . . . . 23
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . 24
Normative References . . . . . . . . . . . . . . . . . . . . 25
Informative References . . . . . . . . . . . . . . . . . . . 26
Author's Address . . . . . . . . . . . . . . . . . . . . . . 27
Intellectual Property and Copyright Statements . . . . . . . 28

1. Introduction

The Session Initiation Protocol for Instant Messaging and Presence
Leveraging Extensions (SIMPLE) working group has been developing
specifications for subscribing to,

In many communications applications, such as Voice over IP, instant
messaging, and receiving notifications of,
user presence [10]. An important aspect of user presence presence, it is
authorization policy. Indeed, the presence specification requires a
Presence Agent (PA) necessary for network servers to both authenticate and authorize all
subscriptions before accepting them. However, it does not define how
the server determines
access per-user information in the authorization status process of servicing a subscriber. Users
can set their authorization policy through web pages or voice
response systems. However, there is currently no protocol specified
for setting this policy. A protocol for this purpose request.
This per-user information resides within the network, but is called an
authorization manipulation protocol.

Mechanisms have also been defined to support reactive authorization
[11][12]. Reactive authorization allows managed
by the end user to themselves. Its management can be informed when
someone has attempted to subscribe to their presence when done through a
multiplicity of access points, including the server
is unable to determine an authorization policy. The user can then go
and set an web, a wireless handset,
or a PC application.

Examples of per-user information are presence [12] authorization
policy for the subscriber, using the same
unspecified mechanism for setting the policy.

Another important aspect of and presence systems is the buddy list, also
known as the lists. Presence lists are lists of users whose
presence list. This is desired by a watcher. Presence information for the list
of users that a watcher
wishes to learn presence state for. This list can be stored in the
client, or it can be stored in obtained by subscribing to a centralized server. resource which
represents that list [15]. In the latter this case, the client would subscribe Resource List Server
(RLS) requires access to the list as a whole [13]. The
presence this list can be set by using a web page or voice response
application. However, there is no protocol mechanism currently
specified in order to manage the presence list. Such a protocol is called process a
presence list manipulation protocol.

The SIMPLE group has defined requirements SIP
[11]SUBSCRIBE [20] request for it. Requirements for an authorization manipulation protocol and a of
presence list manipulation protocol.
These protocols have similar requirements, lists and are captured in [14]. authorization policies have been specified by the
SIMPLE working group [16].

This document proposes specification describes a candidate for the authorization and presence
manipulation protocol, protocol that can be used to
manipulate this per-user data. It is called the Extensible Markup
Language (XML) Configuration Access Protocol (XCAP). XCAP is not actually a
new protocol. XCAP Rather, it is a set of conventions for using mapping XML
documents and document components into HTTP to read, write URIs, rules for how the
modification of one resource affects another, data validation
constraints, and modify XML configuration authorization policies associated with access to
those resources. Because of this structure, normal HTTP primitives
can be used to manipulate the data. XCAP is based heavily on ideas
borrowed from the Application Configuration Access Protocol (ACAP)
[15],
[18], but it is not an extension of it, nor does it have any
dependencies on it. Like ACAP, XCAP is meant to support the
configuration needs for a multiplicity of applications, rather than
just a single one.

2. Overview of Operation

XCAP supports the needs of any application that needs access to data
defined by clients of the application.

Each application that makes use of XCAP specifies an application
usage (Section 4). This application usage defines the XML schema [1]
for the data used by the application, along with other key pieces of
information. The principal task of XCAP is to allow clients to read,
write, modify, create and delete pieces of that data. These
operations are supported using HTTP 1.1 [2]. An XCAP server acts as a
repository for collections of XML documents. There will be documents
stored for each application. Within each application, there are
documents stored for each user. Each user can have a multiplicity of
documents for a particular application. To access some component of
one of those documents, XCAP defines an algorithm for constructing a
URI that can be used to reference that component. Components refer to
any subtree of the document, or any attribute for any element within
the document. Thus, the HTTP URIs used by XCAP point to pieces of
information that are finer grained than the XML document itself.

With a standardized naming convention for mapping components of XML
documents,
documents to HTTP URIs, the basic operations for accessing the data
are simple. provided by existing HTTP primitives. Reading one of the
components is just a standard accomplished with HTTP GET operation.
Writing, GET, creating or modifying one
of the components is a standard
HTTP POST or PUT operation. Deleting a component is just a standard
DELETE operation. For example, to add a friend to a presence list, a
client would construct done with an XML document fragment which contains the
information on that friend. The client would then construct a URI
that refers to the location in the presence list document where this
new fragment is to be added. The client then performs a POST
operation against the URI, placing the document fragment into the
body HTTP PUT, and removing one of the POST request.
components is done with an HTTP DELETE. To provide atomic read/modify/write read/
modify/write operations, the HTTP If-Unmodified-Since header field is entity tags are used. The
HTTP POST operation used by the client would contain the date
obtained in the Last-Modified header field from the GET used to read
the data.

3. Terminology

In this document, the key words "MUST", "MUST NOT", "REQUIRED",
"SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY",
and "OPTIONAL" are to be interpreted as described in RFC 2119 [3] and
indicate requirement levels for compliant implementations.

4. Application Usages

A central concept in XCAP is that of an application usage. An
application usage defines the way in which a specific application
makes use of XCAP. This definition is composed of several pieces of
information, such as an XML schema and constraints on values of one
element given values in another.

Application usages are documented in specifications which convey this
information. In particular, an application usage specification MUST
provide the following information:

Application Usage ID (AUID): Each application usage is associated
with a name, called an AUID. This name uniquely identifies the
application usage, and is different from all other AUIDs. AUIDs
exist in one of two namespaces. The first namespace is the IETF
namespace. This namespace contains a set of tokens, each of which
is registered with IANA. These registrations occur with the
publication of standards track RFCs [16] [19] based on the guidelines
in Section 10. The second namespace is the vendor-proprietary
namespace. Each AUID in that namespace is prefixed with the token
"vnd", followed by a period ("."),
reverse domain name name of the organization creating the AUID,
followed by a valid DNS name,
followed by another period, followed by any vendor defined token.
A vendor creating such an AUID MUST only create one using domain
names for which it is an administrator. As an
example, the example.com domain can create an AUID with the value
"vnd.example.com.foo"
"com.example.foo" but cannot create one with the value
"vnd.example.org.bar".
"org.example.foo". AUIDs within the vendor namespace do not need
to be registered with IANA. The vendor namespace is also meant to
be used in lab environments where no central registry is needed.
The syntax for AUIDs, expressed in ABNF [7] (and using some of the
BNF defined in RFC 2396 [8]) is:

AUID = global-auid / vendor-auid
global-auid = auid
auid = alphanum / mark
vendor-auid = rev-hostname "." auid
rev-hostname = toplabel *( "." domainlabel )
domainlabel = alphanum
/ alphanum *( alphanum / "-" ) alphanum
toplabel = ALPHA / ALPHA *( alphanum / "-" ) alphanum

MIME Type: Each application usage MUST register a MIME type for its
XML documents. This is done based on the procedures of RFC 3023
[4].

XML Schema: Each application will have a unique schema which defines
the data needed by the application. In XCAP, this schema is
represented using XML schema. As an example, presence list data
is composed of a list of URIs, each of which represends a member
of presence list. [17] defines the XML schema for this data. [1].

Additional Constraints: XML schemas can represent a variety of
constraints about data, such as ranges and types. However, schemas
cannot cover all types of data constraints, including constraints
introduced by data interdependencies. For example, one XML element
may contain an integer which defines the maximum number of
instances of another element. The application usage defines these
additional constraints.

Data Semantics: The application usage needs to define detailed
semantics for each piece of data in the schema.

Naming Conventions: The data defined by the XML schema will be used
by any number of entities participating in the application. In the
case of presence list, the data is used by the Resource List
Server (RLS), which reads the data, and by the clients, which
write it. During the execution of the application (i.e., the
processing of the list subscription), specific documents will need
to be read or written. In order for the application to function
properly, there needs to be agreement on exactly which documents
are read or written by the application. This is an issue of naming
conventions; agreeing on how an application constructs the URI
representing the document that is to be read or written. The
application usage spells out this information.

Computed Data: Frequently, some of the data defined in the schema
is not independent; that is, its value depends on the values of
other elements in the document. As a result,

Resource Interdependencies: In many cases, when a client uses user modifies an
XCAP resource, many other resources need to modify the independent pieces of the document, the server
needs to compute the dependent ones in order to fully populate the
document. The change as well. Such
interdependencies are application usage needs to define which data
components are dependent, and how they are computed. dependent. As an example,
when the URI for a presence list is not specified by user performs a
client, PUT operation to create a URI is chosen by new presence
list, the server and filled in. This needs may need to fill in the URI associated with that
list. These interdependencies need to be specified by the
application usage. Note that, if a server needs to modify data
within a document just PUT by the client, this modification is
effectively accomplished as a separate transaction. Concretely,
this means that, after the server modifies the data, the entity
tags are updated as if the client had made the change itself.

Authorization Policies: By default, an XCAP server will only allow a
user to access (read, write, delete or modify) their own
documents. The application usage can specify differing default
authorization policies. Of course, An application usage can also specify
whether another application usage is used to define the default
authorization policies. An application usage for setting
authorization policies can always also be
overriden by operator or user-specified policies. defined subsequent to the
definition of the the main application usage. In such a case, the
main application usage needs only to specify that such a usage
will be defined in the future.

Application usages are similar to dataset classes in ACAP.

5. URI Construction

In order to manipulate a piece of configuration data, the data must
be represented by an HTTP URI. XCAP defines a specific naming
convention for constructing these URIs. This convention is very
similar to In particular, the naming conventions used for dataset classes in ACAP,
and makes use host part
identifies the XPath [5] specification for identifying nodes of an
XML document. XCAP server. The abs_path component of the HTTP URI consists of two parts:

XCAP-URI = Document-URI ["?" Node-Selector]
Document-URI = http_URL ;from RFC2616
Node-Selector = *uric ;Escape coded LocationPath from XPath

The first part,
identifies the Document-URI, selects a specific XML document. It
is a valid HTTP URL, subject document to the constraints be modified. XCAP servers
organize XML documents in a specific hierarchical fashion, as
described here. The
constraints for constructing this URI are discussed below in Section 5.1. Once The URI MAY contain a document query. This query is selected,
called a node selector. When present, it contains an XML component
identifier formatted according to Section 5.2. The node selector
identifies the remainder specific component of the XML document. The HTTP URI (the
Node-Selector) identifies which components of
without the document are being
addressed. The Node-Selector query is called the document URI. , and makes use the
specification for identifying nodes of an XPath [5] LocationPath expression,
subject to constraints described below. XML document.

5.1 Identifying the XML Document

XCAP mandates that a server organizes documents according to a
defined hierarchy. The root of this hierarchy is an HTTP URI called
the XCAP services root URI. This URI identifies the root of the tree
within the domain where all XCAP documents are stored. It can be any
valid HTTP URL, but MUST NOT contain a query string. As an example,
http://xcap.example.com/services might be used as the XCAP services
root URI within the example.com domain. Typically, the XCAP services
root URI is provisioned into client devices for bootstrapping
purposes.

Beneath the XCAP services root URI is a tree structure for organizing
documents. The first level of this tree consists of the XCAP AUID.
So, continuing the example above, all of the documents used by the
presence list application would be under http://xcap.example.com/
services/presence-lists.

It is assumed that each application will have data that is set by
users, and/or it will have global data that applies to all users. As
a result, within the directory structure for each application usage,
there are two sub-trees. One, called "users", holds the documents
that are applicable to only specific users, and the other, called
"global", holds documents applicable to all users.

Within the "users" tree are zero or more sub-trees, each of which
identifies a documents that apply to a specific user. XCAP does not
itself define what it means for documents to "apply" to a user,
beyond specification of a baseline authorization policy.
Specifically, the default authorization policy is that only a user
who authenticates themself as user X can read, write, or otherwise
access in any way the documents within sub-tree X. Each application
usage can specify additional authorization policies which depend on
data used by the application itself.

The remainder of the URI (the path following "global" or the specific
user) is not constrained by this specification. The application usage
MAY introduce constraints, or may allow any structure to be used.

5.2 Identifying the XML Nodes

The second component of the XCAP URI specifies specific nodes of the
XML document which are to be accessed. Nodes, in this context, A node refers to either an XML
element or an attribute of an element. The node selector is an
expression which identifies an element or attribute. Its grammar is:

node-selector = element-selector ["/" attribute-selector]
element-selector = step *( "/" step)
step = by-name / by-pos / by-attr
by-name = QName ; from XML Namespaces
by-pos = QName "[" position "]"
position = 1*DIGIT
by-attr = QName "[" "@" att-name "=" <">
att-value <"> "]"
att-name = QName
att-value = AttValue ; from XML specification
by-pos = QName "[" position "]"
position = *DIGIT
attribute-selector = "@" att-name

The node selector is based on the definition provided concepts in XPath [5]. Indeed, the
node selector expression happens to be a valid XPath expression.
However, XPath specification, provides a set of functionality far richer than is
needed here, and therefore
includes its breadth would introduce complexity into XCAP.

To determne the XML elements, attributes, text, namespaces, element or attribute selected by the node
selector, processing
instructions, comments, and roots. These nodes are identified begins at the root of the XML document. The
first step in the element selector is then taken. Each step chooses a
specific XML element within the current document context. The
document context is the point within the XML document from which a
specific step is evaluated. The document context begins at the root
of the document. When a step determines an element within that
context, that element becomes the new context for evaluation of the
next step. Each step can select an element by its name, by a
LocationPath expression,
combination of name and attribute value, or by name and position. If
the step is attempting selection by name, the server looks for all
elements within the current context with that name. Name matching is
performed as defined in XPath. Either described below. If there is more than one element with
the specified name, the result is considered a no-match.

If the step is attempting selection by name and attribute, the server
looks for all elements within the current document context with that
name. Of those that match, it looks for ones that have the abbreviated given
attribute name, where that attribute has the given value. If there is
no match, or unabbreviated form MAY be used.

Contraints are imposed on if more than one element matches, the XPath expression based on result is
considered a no-match.

If the operation
being performed. step is attempting selection by name and position, the server
looks for all elements within the current document context with that
name. These do not constrain are then sorted in document order, as defined by Xpath.
The position-th element is then selected. If there are fewer than
position number of elements with that name, the functions or axes result is considered
a no-match.

Once the last step is executed, if there is no attribute selector,
the result of the node selection is the last selected element. If
there is an attribute selector, the server checks to see if there is
an attribute with that
can be used name within the currently selectoed element.
If there is not, the result is considered a no-match. Otherwise, that
attribute is selected.

Matching of element names and attributes is performed by expanding
them into the expanded name form, as described in XML Namespaces, and
then performing the XPath expression, but rather constrain comparison of the results. When evaluating the
QNames in the
resulting node set. See Section 6 for details. selector, the default namespace and namespace
definitions from the document URI apply.

As an example, consider the following XML document:

<?xml version="1.0"?>
<watcherinfo xmlns="urn:ietf:params:xml:ns:watcherinfo"
version="0" state="full">
<watcher-list resource="sip:professor@example.net" package="presence">
<watcher status="active"
id="8ajksjda7s"
duration-subscribed="509"
event="approved" >sip:userA@example.net</watcher>
<watcher status="pending"
id="hh8juja87s997-ass7"
display-name="Mr. Subscriber"
event="subscribe">sip:userB@example.org</watcher>
</watcher-list>
</watcherinfo>

The node selector "watcherinfo/watcher-list/
watcher[@id="8ajksjda7s"]" would select the following XML element:

<watcher status="active"
id="8ajksjda7s"
duration-subscribed="509"
event="approved" >sip:userA@example.net</watcher>

6. Client Operations

An XCAP client is an HTTP 1.1 compliant client. An XCAP client
performs a set of primitive operations Specific data
manipulation tasks are accomplished by invoking specific methods
against the server, using specific URIs, where the requests contain
bodies and headers subject to specific constraints. The right set of
primitive operations, the HTTP
methods used to accomplish them, and with the
header and body constraints are described here. right set of headers on the server. This section
describes those in detail

6.1 Creating a New Document

To create a new document, the client constructs a URI that references
the location where the document is to be placed. This URI MUST NOT
contain a NodeSelector component, and MUST meet the constraints
described in Section 5.1. component. The client then invokes a PUT
method on that URI.

The content in the request MUST be an XML document compliant to the
schema associated with the application usage defined by the URI. For
example, if the client performs a PUT operation to http://
xcap.example.com/services/presence-lists/users/joe/mybuddies,
presence-lists is the application unique ID, and the schema defined
by it would dictate the body of the request.

6.2 Replace an Existing Document

To replace an existing document with a new one, the procedures of
Section 6.1 are followed; the Request-URI merely refers to an
existing document which is to be replaced with the content of the
request.

6.3 Deleting a Document

To delete a document, the client constructs a URI that references the
document to be deleted. By definition this URI will not contain a
NodeSelector component. The client then invokes a DELETE operation on
the URI to delete the document.

6.4 Fetching a Document

As one would expect, fetching a document is trivially accomplished by
performing an HTTP GET request with the Request URI set to the
document to be fetched. It is useful for clients to perform
conditional GETs using the If-Modified-Since If-Match header field, in order to check
if a locally cached copy of the document is still valid. An HTTP
server MUST return Etags for entities that represent resources
managed by XCAP.

6.5 Creating a New Element

To create a new XML element within an existing document, the client
constructs a URI whose Document-URI document URI points to the document to be
modified. The Node-Selector node selector MUST be present, containing an expression
identifying the point present in the document where URI. The node
selector is constructed such that it meets two constraints. First, if
evaluated against the new element current document, the result is a no-match.
Secondly, if the element was added to be
added. The node-set selected the document as desired by the expression MUST contain only a
single XML
client, the node selector would select that element.

The client then invokes the HTTP POST method. PUT method [[OPEN ISSUE: what is the
content type?]]. The content in the request MUST be an XML document. That XML document MUST be conformant
to the schema associated with the application usage defined by the
URI. element.
The server will insert the element into the document such that the first element
of the document becomes
node selector, if evaluated by the next sibling immediately following server, would return the
element specified by content
present in the Request-URI. request. The client SHOULD be certain, before making
the request, that the resulting modified document will also be
conformant to the schema.

6.6 Replacing an Element in

It is important to note that the Document

Replacing an element of might potentially be
inserted in the document constitutes storage of a
supplied entity under the specified URI, in several different ways, and is therefore
accomplished with the PUT method (as opposed to POST, which will
insert). The client constructs a URI whose Document-URI points to the
document to be modified. The Node-Selector MUST be present,
containing an expression identifying still meet
the element whose value constraints defined above. This is analagous to be
replaced. The node-set selected by the expression MUST contain only case when a
single XML element.

The client then invokes the
new file is PUT method. The entity of the request
MUST be of type text/plain. The server will take into a directory on a server; the value location of that
file within the
element specified by the request URI, directory is not specified, and replace it with the content
of is up the PUT request. Here, value refers local file
system to the binary contents of decide. The only guarantee is that GET(PUT(x)) returns
document x.

6.6 Replacing an
XML document, starting with the beginning tag of the element, and
ending with the end tag. This differs from the "string value" defined Element in XPath, which refers only to the values of the text Document

Replacing an element
descendants of an element. The client SHOULD be certain, before
making the request, that the resulting modified document will be
conformant to the schema. is also accomplished with PUT.
The body of only difference with the request here behavior above for insertion is of type text/plain because that the value
of an element need not be a valid XML document; frequently, it will
be text or CDATA. Of course,
node selector, when evaluated against the value of current document, is a
match for an XML element may be other
XML elements, in which case the body of the request will be an XML
document fragment, current document. That element is
removed, and by itself not compliant to any schema.

Note that this operation only modifies the value of an element. It
cannot modify replaced with the attributes content of the element. To do that, the replace
attribute operation is performed. PUT request.

6.7 Delete an Element

To delete elements from a document, the client constructs a URI whose
Document-URI
document URI points to the document containing the elements to be
deleted. The Node-Selector node selector MUST be present, containing an expression
identifying and identify the elements specific
element to be deleted. Unlike most of the other
operations, the node-set selected by the expression MAY contain
multiple elements.

The client then invokes the HTTP DELETE method. All of the elements
specified by the node set The server will be deleted by
remove the server. The body of element from the request SHOULD be empty. document. The client SHOULD be certain,
before making the request, that the resulting modified document will
also be conformant to the schema.

6.8 Fetch an Element

To fetch an element of a document, the client constructs a URI whose
Document-URI
document URI points to the document containing the element to be
fetched. The Node-Selector node selector MUST be present, containing an expression
identifying and must identify the
element whose value is to be fetched.

The node-set
selected by the expression MUST contain only a single XML element.

The client then invokes the GET method. The response will contain an
that XML document with the specified element as element. Specifically, it contains the one and only child content of the document root.

OPEN ISSUE: This only allows you to get one element at a time. We
could allow the XPath expression to specify multiple elements, and
then the response contains a document XML
document, starting with each of those elements
as a child of the document root. However, that document might not
be compliant to opening bracket for the schema, begin tag for
that element, and worse, ending with the document doesnt
actually reflect any specific sub-tree of closing bracket for the actual document. end tag for
that element.

6.9 Create an Attribute

To create an attribute in an existing element of a document, the
client constructs a URI whose Document-URI document URI points to the document to
be modified. The Node-Selector node selector MUST be present, containing an
expression identifying an attribute present. The node selector is
constructed such that it meets two constraints. First, if evaluated
against the current document, the result is a no-match. Secondly, if
the attribute was added to created. Specifically, the last location step of document as desired by the expression MUST specify an attribute
axis, and client, the context MUST specify a single element
node selector would select that exists
within the document. attribute.

The client then invokes the HTTP POST PUT method. The content defined by
the request MUST be of type text/plain. A new attribute is added compliant to the element grammar for Attribute as defined by the context, with the name specified by
in XML 1.0 [[OPEN ISSUE: content type?]]. The server will add that
attribute such that, if the node test in selector is evaluated on the last location step, with a value specified by
resulting document, it returns the
body of attribute present in the request. If an attribute of this name already exists, it
is replaced.
The client SHOULD be certain, before making the request, that the
resulting modified document will also be conformant to the schema.

6.10 Replacing Attributes

To replace

Replacing an attribute in an existing element of a document, the
client constructs a URI whose Document-URI points to the document to
be modified. The Node-Selector MUST be present, containing an
expression identifying an attribute that is to be replaced. also accomplished with PUT.
The client then invokes only difference with the HTTP PUT method. The content defined by behavior above for insertion is that the request MUST be of type text/plain. The value of
node selector, when evaluated against the current document, is a
match for an attribute
defined by in the Node-Selector current document. That attribute is
removed, and replaced by with the body content of the PUT request.
The client SHOULD be certain, before making the request, that the
resulting modified document will also be conformant to the schema.

6.11 Deleting Attributes

To delete attributes from the document, the client constructs a URI
whose Document-URI document URI points to the document containing the attributes
to be deleted. The Node-Selector node selector MUST be present, containing and evaluate to an
expression identifying
attribute in the attributes document to be deleted. Unlike most of
the other operations, the node-set selected by the expression MAY
contain multiple attributes.

The client then invokes the HTTP DELETE method. All of the attributes
specified by the node set The server will be deleted by
remove the server. The body of attribute from the request SHOULD be empty. document. The client SHOULD be certain,
before making the request, that the resulting modified document will
also be conformant to the schema.

6.12 Fetching Attributes
To fetch an attribute of a document, the client constructs a URI
whose Document-URI points to the document containing the attribute to
be fetched. The Node-Selector node selector MUST be present, containing an
expression identifying the attribute whose value is to be fetched.

The node-set selected by the expression MUST contain only a single
XML attribute.

The client then invokes the GET method. The response will contain an
text/plain
document with the value of the specified attribute.

6.13 Fetching Metadata
Elements and attributes in an XML document have various meta-data
associated with them. For example, and XML element has a certain
number of child elements. That number is a piece of meta-data that
describes the element. Currently, there is no way attribute, formatted according to fetch meta-data
for XML elements or attributes.

OPEN ISSUE: Is this restriction OK? XPath does specify functions
for computing meta-data about node sets. We can't use them since
XCAP mandates that the request URI be a location set, which does
not include these other functions. We could relax
grammar of Attribute as defined in the constraint
if this is deemed important.

6.14 XML 1.0 specifications.

6.13 Read/Modify/Write Transactions

It is anticipated that a common operation will be to read the current
version of a document or element, modify it on the client, and then
write the change back to the server. In order for the results to be
consistent with the client's expectations, the operation must be
atomic.

To accomplish this, the client stores the value makes use of entity tags returned by
the Last-Modified
header field from the response to its server in a GET operation used to read the element, attribute, or
document that is to be modified. To guarantee atomicity, the PUT or POST
operation used to write the changes back to the server MUST contain
an If-Unmodified-Since If-Match header field, whose value is equal to the value entity tag from
the prior GET response. If the request fails with a 412 response, the
client knows that another update of the data has occurred before it
was able to write the results back. The client can then fetch the
most recent version, and attempt its modification again.

Because there are no batching operations defined in HTTP, that would
allow for a number of separate create, modify or delete operations to
be performed atomically, designers of application usages should take
care to structure their schemas so that operations that need to be
performed atomically can be done in a single operation.

7. Server Behavior

TODO: Specify an XML body type for the responses that contains
error conditions or success results.

An XCAP server is an HTTP 1.1 compliant origin server. The behaviors
mandated by this specification relate to the way in which the HTTP
URI is interpreted and the content is constructed.

An XCAP server MUST be explicitly aware of the application usage
against which requests are being made. That is, the server must be
explicitly configured to handle URIs for each specific application
usage, and must be aware of the constraints imposed by that
application usage.

OPEN ISSUE: It may Furthermore, an XCAP server MUST be possible aware of all
of the XML namespaces present in any documents it manages. This is to remove this restriction
ensure that any data constraints or data interdependencies imposed by
allowing an
a future application usage to define operation in a server that
doesnt understand are properly supported by the usage. That may require some capabilities
discovery server. It
is also required to be introduced, this constraint didnt seem ensure that
problematic. authorization policies are properly
implemented.

When the server receives a request, the treatment depends on the URI.
If the URI refers to an application usage not understood by the
server, the server MUST reject the request with a 404 (Not Found)
response. If the URI refers to a user that is not recognized by the
server, it MUST reject the request with a 404 (Not Found).

Next, the server authenticates the request. All XCAP servers MUST
support HTTP Digest [6]. Furthermore, servers MUST support HTTP over
TLS, RFC 2818 [7]. [9]. It is RECOMMENDED that administrators use an HTTPS
URI as the XCAP root services URI, so that the digest client
authentication occurs over TLS.

Next, the server determines if the client has authorization to
perform the requested operation on the resource. The default
authorization policy is that only client X can access (create, read,
write, modify or delete) resources under the "users/X" directory. An
application usage can specify an alternate default authorization
policy specific to that usage. The server may also know of an
application usage that itself defines authorization policies for
another application usage. Of course, an administrator or privileged
user can override the default authorization policy, although this
specification provides no means for doing that.
Generally, if users need to be able to control authorization for
access to XCAP data, an XCAP application usage should be specified
which allows the user to set the policies as needed.

OPEN ISSUE: This is different from ACAP, where authorization
policies are built into the protocol. I think the default
generally will suffice, so I would rather not burden the baseline
protocol with it.

Once authorized, the specific behavior depends on the method and what
the URI refers to.

7.1 POST Handling

If the URI contains only

Resources managed by XCAP do not represent processing scripts. As a
result, POST operations to XCAP URIs is not defined. A server
receiving such a request SHOULD return a 405.

7.2 PUT Handling

The behavior of a Document-URI, the server examines in receipt of a PUT request is as specified
in HTTP 1.1 Section 9.6 - the
entity body content of the request. If there request is no entity in placed at the body,
specified location. This section serves to define the
server MUST reject notion of
"placement" and "specified location" within the context of XCAP
resources.

If the request with URI represents a 409 response. If document (i.e., there is an
entity, but it is not well-formed, no node
selector component), the server MUST reject content of the request
with MUST be a 409 response. If it is well-formed, but not valid XML
document, and MUST be compliant to the schema associated with the
application usage, usage in the server MUST reject URI. If it is not, the request MUST be
rejected with a 409 response. If it is compliant to the schema,
the server MUST store request URI matches a document
that exists on the server, that document at is replaced by the requested URI. content
of the request. If there is the request URI does not already match a document stored at that URI, a 201 (Created) response
code MUST be sent, and it MUST include a Location header field
containing
exists on the value of server, the URI for server adds the document (which will be the
same as the one in the Request-URI). Otherwise, a 200 OK response is
returned, to its repository,
and associates it with the document URI in the body replaces the existing one at
that request URI. For either a 200 or 201 response, the new document is
returned in Note that this may
require the body creation of one or more "directories" on the response, with a Content-Type equal to
the MIME type defined by the application usage. server.

If the Request URI represents an XML element (i.e., it contains a Node-Selector,
node selector, but no attribute selector) the server MUST verify that
the document defined by the Document-URI document URI exists. If no such document
exists on the server, the server MUST reject the request with a 409
response code. If the document does exist, the server
evaluates the Node-Selector as an XPath RelativeLocationPath,
relative to the root The content of the document. If the Node-Selector does not
comply to the grammar for RelativeLocationPath, the server MUST
reject the request with a 400 response code. If the Node-Selector
does comply, and it evaluates to anything other than the empty set, MUST be a single attribute node or single XML
element node, the server MUST reject
the request with a 409 response code.

If the Node-Selector evaluates to the empty set, and the last
location step is on the attribute axis, and associated content (including children elements). If the expression without
the last location step evaluates to a single
request URI matches an element node, within the server
adds an attribute to document, that element. Its name element is the name given in the
node test of the last location step,
removed, and its value is taken from the
body of the request. The server then generates a 200 OK response,
whose body contains the value of the attribute, replaced with a Content-Type
of text/plain.

If the Node-Selector evaluates to a single element node, the server
takes the content of the request, and inserts it into the document
specified by request. If the request
URI such that the selected does not match an element is in the immediate
sibling of document, the nodes defined by server inserts the
content of the request. The
server then generates request as a 200 OK response, whose body contains the
parent element of the new elements just inserted. The parent element
is represented by extracting the contents of in the XML document,
starting with, and including, the begin tag of the element, up to,
and including, the end tag for the element. The Content-Type of such that
the
response resulting document is set compliant to application/xml.

OPEN ISSUE: We can't use the MIME type for schema, and such that the application usage,
since
request URI, when evaluated, would now point to the schema element which was
inserted. There may not allow for the document be more than one way to start with any
element defined by the schema. Is perform such an
insertion; in that OK? I think so.

If the Node-Selector evaluates to a single attribute node, the server
takes the content of the request, and sets case, it as the value of the
attribute specified by the body of the request. The server then
generates a 200 OK response, whose body contains is the value discretion of the
attribute, with a Content-Type of text/plain.

If implementor as
to how it is done. It may also be possible that the result of insertion cannot
be done without other additional elements being inserted, or cannot
be done because the POST new element is a document which does not comply with
the XML schema for compliant to the application usage, schema. In
such a case, the server MUST NOT perform
the POST, and MUST reject the request with return a 409 (Conflict).

7.2 PUT Handling

When the Request URI contains only the Document-URI, the semantics of
PUT are as defined in HTTP 1.1 Section 9.6 - the content of response code. In all
cases, the
request is placed at resulting document MUST be compliant to the specified location. schema.

If the Request URI represents an XML attribute (i.e., it contains a Node-Selector,
node selector and an attribute selector) the server MUST verify that
the document defined by the Document-URI document URI exists. If no such document
exists on the server, the server MUST reject the request with a 409
response code. If the document does exist, the server
evaluates the Node-Selector as an XPath RelativeLocationPath,
relative to the root The content of the document. If the Node-Selector does not
comply request MUST be a single XML
attribute, compliant to the grammar for RelativeLocationPath, the server MUST
reject Attribute as defined in XML
1.0 (i.e., name=value). If the request with a 400 response code. If URI matches an ent within the Node-Selector
does comply,
document, that attribute is removed, and it evaluates to anything other than replaced with the a single
element node or attribute node, content of
the server MUST reject request. If the request
with a 409 response code.

If URI does not match an attribute in the Node-Selector evaluates to a single element node,
document, the server
takes inserts the content of the request, and replaces request as a new
attribute in the value of document, such that
element (where value is defined as all of the content - elements,
text, or CDATA - between resulting document is
compliant to the begin schema, and end tags of the element) with such that content. The server then returns a 200 OK response.

OPEN ISSUE: PUT is not quite right here, since a subsequent GET on
the same URI will not return exactly the same thing - request URI, when
evaluated, would now point to the begin
and end tags will be present. This attribute which was inserted. There
may need to be POST, but then,
how more than one way to differentiate a replace with perform such an append operation?

If the Node-Selector evaluates to a single attribute node, the server
takes the content of the request, and sets insertion; in that case,
it as is the value discretion of the
attribute. implementor as to how it is done. It then returns a 200 OK response.

If may
also be possible that the result of insertion cannot be done without other
additional content being inserted, or cannot be done because the PUT new
attribute is a document which does not comply with the
XML schema for compliant to the application usage, schema. In such a case, the server
MUST NOT perform return a 409 response code. In all cases, the
PUT, and resulting document
MUST reject be compliant to the request with schema.

If the creation or insertion was successful, the server returns a 409 (Conflict). 200
OK or 201 Created, as appropriate.

7.3 GET Handling

The semantics of GET are as specified in RFC 2616. This section
clarifies the specific content to be returned for a particular URI
that represents an XCAP resource.

If the request URI contains only a Document-URI, document URI, the server returns
the document specified by the URI if it exists, else returns a 404
response. If the request URI specifies contains a Node-Selector, the server verifies node selector, and that the document specified by the Document-URI exists. If it does
not exist, the server returns a 404 (Not Found) response. If the
document does exist, the server evaluates the Node-Selector as node
selector identifies an
XPath RelativeLocationPath, relative to XML element in an existing document, that
element is returned in the root 200 response. The content of the document. If
the Node-Selector does not comply to the grammar for
RelativeLocationPath, the server MUST reject the request with a 400 response code. If the Node-Selector does comply, and it evaluates to
anything other than the a single element node or attribute node, the
server MUST reject the request with a 409 response code.

If the Node-Selector evaluates to a single element node,
is the server
takes portion of the XML document text, starting with, and including, with the left bracket of
the begin tag of the element, up to, and including, ending with the right bracket of the
end tag for the element,
and places it into the body of a 200 OK response, setting the
Content-Type to application/xml. element. If the Node-Selector evaluates to request URI contains a single node selector,
and that node selector contains an attribute node, the server
takes selector, and that
attribute exists in the value of specified document, the attribute and server returns it that
attribute, formatted as Attribute in the content of the
200 OK response, setting XML 1.0 specifications. In
all cases, if the Content-Type to text/plain.

OPEN ISSUE: Do we need to say anything about HEAD? We havent said
anything about meta-data so far; most of that referenced resource does not exist, a 404 is just regular HTTP
usage, I think.
returned.

7.4 DELETE Handling

The semantics of DELETE are as specified in RFC 2616. This section
clarifies the specific content to be deleted for a particular URI
that represents an XCAP resource.

If the request URI contains only a Document-URI, the server deletes
the document specified by the URI if it exists and returns a 200 OK
response, else returns a 404 response. If the request URI specifies a
Node-Selector, the server verifies that the document specified by the
Document-URI exists. If it does not exist, the server returns a 404
(Not Found) response. If the document does exist, and the server evaluates the Node-Selector as node
selector specifies an
XPath RelativeLocationPath, relative to the root of XML element that exists, that element is
removed from the document. If the Node-Selector does not comply to the grammar for
RelativeLocationPath, the server MUST reject the request with a 400
response code. If the Node-Selector document does comply, exist, and it evaluates to
the empty set, the server MUST reject the request with a 404 (Not
Found).

Otherwise, the server removes all of the data defined by the
node-set. Specifically, any elements in the node set are removed from
the document, and any attributes
selector specifies an XML attribute that exists in the node set are document, that
attribute is removed from the document. It then returns a 200 OK response. If the result node selector returns
a no-match, a 404 (Not Found) is returned. However, if removal of the deletion is
element or attribute would result in a document which does not comply
with the XML schema for the application usage, the server MUST NOT
perform the deletion, and MUST reject the request with a 409
(Conflict).

7.5 Managing Modification Times Etags

An XCAP server MUST maintain modification times entity tags for all resources that can
be referenced by a URI. Specifically, this means that each document,
and within the document, each element and attribute, MUST be
associated with a modification time an entity tag maintained by the server. These modification times entity
tags are needed to support condition GET, POST
and conditional PUT and DELETE requests.

When a PUT or POST request is made that creates or replaces a document, the modification time
entity tag of that document and all elements and attributes within is set to the current time.
updated.

When a PUT request is made to a URI referencing an XML element, the modification time
entity tag of that element element, its attributes, and all of its enclosed
children and their attributes is
set to the current time. Furthermore, updated. For a PUT or DELETE request
for an XML element, the modification time entity tag of all elements which are
ancestors of that element have their modification
time set to the current time. are updated. However, the modification times entity tags of
attributes belong belonging to elements that are ancestors of the modified
element do not have their modification times entity tags changed, because those
resources have not actually changed.

When a POST PUT request is made to a URI referencing an XML element, the
modification time of all of the elements and their attributes within
the document in the body of the request is set to the current time.
Furthermore, attribute, the modification time
entity of the element which that attribute is the new
parent of the elements in the request, and all of its ancestors, have
their modification time set to the current time. However, the
modification times of their attributes are unchanged.

When updated. For a POST PUT or DELETE request is made to a URI referencing for
an XML attribute, the modification time of that attribute, entity tags for its element, and all elements that
are ancestors of that element is set to the current
time.

When a DELETE request is made to a URI referencing an element, the
modification time of all ancestors of that element is set to the
current time. When a DELETE request is made to a URI referencing an
attribute, the modification time of its element, and all ancestors of
that element, is set to the current time. are updated.

8. Examples

This section goes through several examples, making use of the
presence-lists
resource-lists [17] XCAP application usage.

First, a user Bill creates a new presence-list, resource-list, initially with no
users in it:

PUT
http://xcap.example.com/services/presence-lists/users/bill/fr.xml HTTP/1.1
Content-Type:application/presence-lists+xml

<?xml version="1.0" encoding="UTF-8"?>
<presence-lists
<resource-lists xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<list name="friends" uri="sip:friends@example.com" subscribable="true"> subscribeable="true">
</list>
</presence-lists>
</resource-lists>

Next, Bill adds an entry to the list:

PUT
http://xcap.example.com/services/presence-lists/users/bill/fr.xml?
presence-lists/list[@name="friends"]
resource-lists/list[@name="friends"]/entry HTTP/1.1
Content-Type:text/plain

<entry name="Bill" uri="sip:bill@example.com">
<display-name>Bill Doe</display-name> name="Bob" uri="sip:bob@example.com">
<display-name>Bob Jones</display-name>
</entry>

Note how the URI in the PUT request selects

Next, Bill fetches the list element whose
name attribute is "friends". The body of that request replaces list:

GET
http://xcap.example.com/services/presence-lists/users/bill/fr.xml HTTP/1.1

And the
existing value of that element, which was empty. result is:

HTTP/1.1 200 OK
Etag: "wwhha"
Content-Type: application/xml

<?xml version="1.0" encoding="UTF-8"?>
<resource-lists xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<list name="friends" uri="sip:friends@example.com"
subscribeable="true">
<entry name="Bob" uri="sip:bob@example.com">
<display-name>Bob Jones</display-name>
</entry>
</list>
</resource-lists>

Next, Bill adds another entry to the list, which is another list that
has three entries:

POST

PUT
http://xcap.example.com/services/presence-lists/users/bill/fr.xml?
presence-lists/list[@name="friends"]/entry[@name="Bill"]
presence-lists/list[@name="friends"]/list[@name="close-friends"] HTTP/1.1
Content-Type:text/plain

<list name="close-friends" uri="sip:close-friends@example.com"
subscribable="true">
subscribeable="true">
<entry name="Joe" uri="sip:joe@example.com">
<display-name>Joe Smith</display-name>
</entry>
<entry name="Nancy" uri="sip:nancy@example.com">
<display-name>Nancy Gross</display-name>
</entry>
<entry name="Petri" uri="sip:petri@example.com">
<display-name>Petri Aukia</display-name>
</entry>
</list>

Then, Bill decides he doesnt want Petri on the list, so he deletes
the entry:

DELETE
http://xcap.example.com/services/presence-lists/users/bill/fr.xml?
presence-lists/list/list/entry[@name="Petri"] HTTP/1.1

Bill decides to check on the URI for Nancy:

GET
http://xcap.example.com/services/presence-lists/users/bill/fr.xml?
presence-lists/list/list/entry[@name="Nancy"]/@uri HTTP/1.1

and the server responds:

HTTP/1.1 200 OK
Etag: "ad88"
Content-Type:text/plain

sip:nancy@example.com

uri="sip:nancy@example.com"

9. Security Considerations

Frequently, the data manipulated by XCAP contains sensitive
information. To avoid eavesdroppers from seeing this information,
XCAP RECOMMENDS it
is RECOMMENDED that an admistrator hand out an https URI as the XCAP
root services URI. This will result in TLS-encrypted communications
between the client and server, preventing any eavesdropping.

Client and server authentication are also important. A client needs
to be sure it is talking to the server it believes it is contacting.
Otherwise, it may be given false information, which can lead to
denial of service attacks against a client. To prevent this, a client
SHOULD attempt to upgrade [8] [10] any connections to TLS. Similarly,
authorization of read and write operations against the data is
important, and this requires client authentication. As a result, a
server SHOULD challenge a client using HTTP Digest [6] to establish
its identity, and this SHOULD be done over a TLS connection.

10. IANA Considerations

This specification instructs IANA to create a new registry for XCAP
application usage IDs (AUIDs).

XCAP AUIDs are registered by the IANA when they are published in
standards track RFCs. The IANA Considerations section of the RFC
must include the following information, which appears in the IANA
registry along with the RFC number of the publication.

Name of the AUID. The name MAY be of any length, but SHOULD be no
more than twenty characters long. The name MUST consist of
alphanum [9] [11] characters only.

Descriptive text that describes the application usage.

Normative References

[1] Thompson, H., Beech, D., Maloney, M. and N. Mendelsohn, "XML
Schema Part 1: Structures", W3C REC REC-xmlschema-1-20010502,
May 2001.

[2] 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.

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

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

[5] Clark, J. and S. DeRose, "XML Path Language (XPath) Version
1.0", W3C REC REC-xpath-19991116, November 1999.

[6] Franks, J., Hallam-Baker, P., Hostetler, J., Lawrence, S.,
Leach, P., Luotonen, A. and L. Stewart, "HTTP Authentication:
Basic and Digest Access Authentication", RFC 2617, June 1999.

[7] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", RFC 2234, November 1997.

[8] Berners-Lee, T., Fielding, R. and L. Masinter, "Uniform
Resource Identifiers (URI): Generic Syntax", RFC 2396, August
1998.

[9] Rescorla, E., "HTTP Over TLS", RFC 2818, May 2000.

[8]

[10] Khare, R. and S. Lawrence, "Upgrading to TLS Within HTTP/1.1",
RFC 2817, May 2000.

[9]

[11] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A.,
Peterson, J., Sparks, R., Handley, M. and E. Schooler, "SIP:
Session Initiation Protocol", RFC 3261, June 2002.

Informative References

[10]

[12] Rosenberg, J., "A Presence Event Package for the Session
Initiation Protocol (SIP)", draft-ietf-simple-presence-10 (work
in progress), January 2003.

[11]

[13] Rosenberg, J., "A Watcher Information Event Template-Package
for the Session Initiation Protocol (SIP)",
draft-ietf-simple-winfo-package-05 (work in progress), January
2003.

[12]

[14] Rosenberg, J., "An Extensible Markup Language (XML) Based
Format for Watcher Information",
draft-ietf-simple-winfo-format-04 (work in progress), January
2003.

[13] Rosenberg, J.,

[15] Roach, A. A., Rosenberg, J. and B. Campbell, "A Session Initiation
Protocol (SIP) Event Notification Extension for Resource
Lists", draft-ietf-simple-event-list-04 (work in progress),
June 2003.

[14]

[16] Rosenberg, J. and M. Isomaki, "Requirements for Manipulation of
Data Elements in Session Initiation Protocol (SIP) for Instant
Messaging and Presence Leveraging Extensions (SIMPLE) Systems",
draft-ietf-simple-data-req-02
draft-ietf-simple-data-req-03 (work in progress), April June 2003.

[15]

[17] Rosenberg, J., "An Extensible Markup Language (XML)
Configuration Access Protocol (XCAP) Usage for Presence
Lists", draft-ietf-simple-xcap-list-usage-00 (work in
progress), June 2003.

[18] Newman, C. and J. Myers, "ACAP -- Application Configuration
Access Protocol", RFC 2244, November 1997.

[16]

[19] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA
Considerations Section in RFCs", BCP 26, RFC 2434, October
1998.

[17] Rosenberg, J., "An Extensible Markup Language (XML)
Configuration Access

[20] Roach, A., "Session Initiation Protocol (XCAP) Usage for Presence Lists",
draft-rosenberg-simple-xcap-list-usage-00 (work in progress),
May 2003. (SIP)-Specific Event
Notification", RFC 3265, June 2002.

Author's Address

Jonathan Rosenberg
dynamicsoft
600 Lanidex Plaza
Parsippany, NJ 07054
US

Phone: +1 973 952-5000
EMail: jdrosen@dynamicsoft.com
URI: http://www.jdrosen.net

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