Internet Engineering Task Force SIMPLE WG
Internet Draft J. Rosenberg
dynamicsoft
draft-ietf-simple-winfo-format-02.txt
May 20, 2002
Expires: October 2002
An Extensible Markup Language (XML) Based Format
for Watcher Information
STATUS OF THIS MEMO
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026.
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Abstract
Watchers are defined as entities that request (i.e., subscribe to)
information about a resource. There is fairly complex state
associated with these subscriptions. The union of the state for all
subscriptions to a particular resource is called the watcher
information for that resource. This state is dynamic, changing as
subscribers come and go. As a result, it is possible, and indeed
useful, to subscribe to the watcher information for a particular
resource. In order to enable this, a format is needed to describe the
state of watchers on a resource. This specification describes an XML
document format for such state.
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Table of Contents
1 Introduction ........................................ 3
2 Terminology ......................................... 3
3 Structure of Watcher Information .................... 3
4 Computing Watcher Lists from the Document ........... 5
5 Example ............................................. 6
6 XML Schema .......................................... 7
7 Security Considerations ............................. 9
8 IANA Considerations ................................. 9
8.1 application/watcherinfo+xml MIME Registration ....... 9
8.2 URN Sub-Namespace Registration for
urn:ietf:params:xml:ns:watcherinfo ............................. 10
9 Contributors ........................................ 10
10 Acknowledgements .................................... 12
11 Authors Addresses ................................... 12
12 Normative References ................................ 12
13 Informative References .............................. 13
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1 Introduction
Watchers are defined as entities that request (i.e., subscribe to)
information about a resource, using the SIP Events framework [1].
There is fairly complex state associated with these subscriptions.
This state includes the identity of the subscriber, the state of the
subscription, and so on. The union of the state for all subscriptions
to a particular resource is called the watcher information for that
resource. This state is dynamic, changing as subscribers come and go.
As a result, it is possible, and indeed useful, to subscribe to the
watcher information for a particular resource. An important
application of this is the ability of a user to find out the set of
subscribers to their presentity [11]. This would allow the user to
provide an authorization decision for the subscription.
To support subscriptions to watcher information, two components are
needed. The first is the definition of a SIP Events package for
watcher information. The other is the definition of a data format to
represent watcher information. The former is specified in [2], and
the latter is specified here.
2 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.
This document also uses the terms subscriber, watcher, subscription,
notification, watcherinfo subscription, watcherinfo subscriber, and
watcherinfo notification with the meanings described in [2].
3 Structure of Watcher Information
Watcher information is an XML document [4] that MUST be well-formed
and SHOULD be valid. Watcher information documents MUST be based on
XML 1.0 and MUST be encoded using UTF-8. This specification makes use
of XML namespaces for identifying watcherinfo documents and document
fragments. The namespace URI for elements defined by this
specification is a URN [5], using the namespace identifier 'ietf'
defined by [6] and extended by [7]. This URN is:
urn:ietf:params:xml:ns:watcherinfo
A watcher information document begins with the root element tag
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"watcherinfo". It consists of any number of "watcher-list" sub-
elements, each of which is a list of watchers for a particular
resource. Other elements from different namespaces MAY be present for
the purposes of extensibility; elements or attributes from unknown
namespaces MUST be ignored. There are two attributes associated with
this element, both of which MUST be present:
version: This attribute allows the recipient of watcherinfo
documents to properly order them. Versions start at 0, and
increment by one for each new document sent to a
subscriber. Versions are scoped within a subscription.
Versions MUST be representable using a 32 bit integer.
state: This attribute indicates whether the document contains
the full watcherinfo state, or whether it contains only
information on those watchers which have changed since the
previous document (partial).
Each "watcher-list" element contains the set of watchers on a
particular resource. Other elements from different namespaces MAY be
present for the purposes of extensibility; elements or attributes
from unknown namespaces MUST be ignored. There are two attributes
associated with this element, both of which MUST be present:
resource: This attribute contains a URI for the resource being
watched by that list of watchers. It is mandatory.
package: This attribute contains a string indicating the event
package for which watcher information on that resource is
being provided. It is mandatory.
The "watcher" element describes a watcher in the watcher list. The
value of the "watcher" element is a URI for the watcher. This URI
SHOULD be an address-of-record (for example, sip:joe@example.com) as
opposed to a device address (for example, sip:joe@192.0.2.3). There
are three mandatory attributes which MUST be present:
id: A unique identifier for the subscription described by the
watcher element. The id MUST be representable using the
grammar for token as specified by SIP [8]. It MUST be
unique across all other watchers reported in documents sent
in notifications for a particular watcherinfo subscription.
status: The status of the subscription. The meaning of the
various statuses are defined in the watcher information
event package [2].
event: The event which caused the transition to the current
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status. The events are defined in the watcher information
event package [2].
There are also some optional, informative attributes of the watcher
element. These are:
display-name: A textual representation of the name of the
subscriber.
expiration: The amount of time, in seconds from the current
time, that the subscription will expire.
duration-subscribed: The amount of time, expressed in seconds,
between the time the SUBSCRIBE which created the
subscription was received, and the current time.
The xml:lang attribute MAY be used with the "watcher" element to
specify the language of the "display-name".
The number of watchers present for each resource, and the set of
resources listed, depends on the type of data being provided, and to
whom.
For example, consider a presence system using watcher information.
In one scenario, a user, A, subscribes to the presence of another
user, B. A would like to find out about the status of their
subscription. To do so, A subscribes to the watcher information for
B's presence. A does not have authorization to learn the status of
all watchers for B's presence. As a result, the watcher information
sent to A will contain only one watcher - A themself.
In another scenario, a user B, wishes to learn the set of people who
have subscribed to B's presence. To do this, B subscribes to the
watcher information for B's presence. Here, B is authorized to see
all the watchers of B's presence. As a result, the watcher
information sent to B will contain all watchers of B's presence.
In the case where an administrator wishes to learn the current status
in the system, the watcher information could contain all watchers for
all resources.
4 Computing Watcher Lists from the Document
Typically, the NOTIFY for watcherinfo will only contain information
about those watchers whose state has changed. To construct a coherent
view of the total state of all watchers, a watcherinfo subscriber
will need to combine NOTIFYs received over time. The watcherinfo
subscriber maintains a table for each watcher list it receives
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information for. Each watcher list is uniquely identified by the URI
in the "resource" attribute of the "watcher-list" element. Each table
contains a row for each watcher in that watcher list. Each row is
indexed by the unique ID for that watcher. It is conveyed in the "id"
attribute of the "watcher" element. The contents of each row contain
the state of that watcher as conveyed in the "watcher" element. The
tables are also associated with a version number. The version number
MUST be initialized with the value of the "version" attribute from
the "watcherinfo" element in the first document received. Each time a
new document is received, the value of the local version number, and
the "version" attribute in the new document, are compared. If the
value in the new document is one higher than the local version
number, the local version number is increased by one, and the
document is processed. If the value in the document is more than one
higher than the local version number, the local version number is set
to the value in the new document, the document is processed, and the
watcherinfo subscriber SHOULD generate a refresh request to trigger a
full state notification. If the value in the document is less than
the local version, the document is discarded without processing.
The processing of the watcherinfo document depends on whether it
contains full or partial state. If it contains full state, indicated
by the value of the "state" attribute in the "watcherinfo" element,
the contents of all tables associated with this watcherinfo
subscription are flushed. They are repopulated from the document. A
new table is created for each "watcher-list" element, and a new row
in each table is created for each "watcher" element. If the
watcherinfo contains partial state, as indicated by the value of the
"state" attribute in the "watcherinfo" element, the document is used
to update the existing tables. For each "watcher-list" element, the
watcherinfo subscriber checks to see if a table exists for that list.
This check is done by comparing the URI in the "resource" attribute
of the "watcher-list" element with the URI associated with the table.
If a table doesn't exist for that list, one is created. For each
"watcher" element in the list, the watcherinfo subscriber checks to
see whether a row exists for that watcher. This check is done by
comparing the ID in the "id" attribute of the "watcher" element with
the ID associated with the row. If the watcher doesn't exist in the
table, a row is added, and its state is set to the information from
that "watcher" element. If the watcher does exist, its state is
updated to be the information from that "watcher" element. If a row
is updated or created, such that its state is now terminated, that
entry MAY be removed from the table at any time.
5 Example
The following is an example of watcher information for a presentity,
who is a professor. There are two watchers, one from a university,
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and another from an organization.
<?xml version="1.0"?>
<watcherinfo xmlns="urn:ietf:params:xml:ns:watcherinfo"
version="0" state="full">
<watcher-list resource="sip:professor@university.edu" package="presence">
<watcher status="active"
id="8ajksjda7s"
duration-subscribed="509"
event="approved" >sip:subcriber@university.edu</watcher>
<watcher status="pending"
id="hh8juja87s997-ass7"
display-name="Mr. Subscriber"
event="subscribe">sip:subcriber@organization.org</watcher>
</watcher-list>
</watcherinfo>
6 XML Schema
The following is the schema definition of the watcherinfo document
format:
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
targetNamespace="urn:ietf:params:xml:ns:watcherinfo"
xmlns:tns="urn:ietf:params:xml:ns:watcherinfo" >
<!-- This import brings in the XML language attribute xml:lang-->
<xs:import namespace="http://www.w3.org/XML/1998/namespace"
schemaLocation="http://www.w3.org/2001/03/xml.xsd" />
<xs:element name="watcherinfo">
<xs:complexType>
<xs:sequence>
<xs:element ref="tns:watcher-list" minOccurs="0"
maxOccurs="unbounded"/>
<xs:any namespace="##other" processContents="lax" minOccurs="0"
maxOccurs="unbounded"/>
</xs:sequence>
<xs:attribute name="version" type="xs:nonNegativeInteger"
use="required"/>
<xs:attribute name="state" use="required">
<xs:simpleType>
<xs:restriction base="xs:string">
<xs:enumeration value="full"/>
<xs:enumeration value="partial"/>
</xs:restriction>
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</xs:simpleType>
</xs:attribute>
</xs:complexType>
</xs:element>
<xs:element name="watcher-list">
<xs:complexType>
<xs:sequence>
<xs:element ref="tns:watcher" minOccurs="0" maxOccurs="unbounded"/>
<xs:any namespace="##other" processContents="lax"
minOccurs="0" maxOccurs="unbounded"/>
</xs:sequence>
<xs:attribute name="resource" type="xs:anyURI" use="required"/>
<xs:attribute name="package" type="xs:string" use="required"/>
</xs:complexType>
</xs:element>
<xs:element name="watcher">
<xs:complexType>
<xs:simpleContent>
<xs:extension base="xs:anyURI">
<xs:attribute name="display-name" type="xs:string"/>
<xs:attribute name="status" use="required">
<xs:simpleType>
<xs:restriction base="xs:string">
<xs:enumeration value="pending"/>
<xs:enumeration value="active"/>
<xs:enumeration value="waiting"/>
<xs:enumeration value="terminated"/>
</xs:restriction>
</xs:simpleType>
</xs:attribute>
<xs:attribute name="event" use="required">
<xs:simpleType>
<xs:restriction base="xs:string">
<xs:enumeration value="subscribe"/>
<xs:enumeration value="approved"/>
<xs:enumeration value="deactivated"/>
<xs:enumeration value="probation"/>
<xs:enumeration value="rejected"/>
<xs:enumeration value="timeout"/>
<xs:enumeration value="giveup"/>
<xs:enumeration value="noresource"/>
</xs:restriction>
</xs:simpleType>
</xs:attribute>
<xs:attribute name="expiration" type="xs:unsignedLong"/>
<xs:attribute name="id" type="xs:string" use="required"/>
<xs:attribute name="duration-subscribed" type="xs:unsignedLong"/>
<xs:attribute ref="xml:lang"/>
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</xs:extension>
</xs:simpleContent>
</xs:complexType>
</xs:element>
</xs:schema>
7 Security Considerations
Watcher information is sensitive information. The protocol used to
distribute it SHOULD ensure privacy, message integrity and
authentication. Furthermore, the protcol should provide access
controls which restrict who can see who elses watcher information.
8 IANA Considerations
This document registers a new MIME type, application/watcherinfo+xml,
and registers a new XML namespace.
8.1 application/watcherinfo+xml MIME Registration
MIME media type name: application
MIME subtype name: watcherinfo+xml
Mandatory parameters: none
Optional parameters: Same as charset parameter application/xml
as specified in RFC 3023 [9].
Encoding considerations: Same as encoding considerations of
application/xml as specified in RFC 3023 [9].
Security considerations: See Section 10 of RFC 3023 [9] and
Section 7 of this specification.
Interoperability considerations: none.
Published specification: This document.
Applications which use this media type: This document type has
been used to support subscriber authorization functions for
SIP-based presence [10] [2].
Additional Information:
Magic Number: None
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File Extension: .wif or .xml
Macintosh file type code: "TEXT"
Personal and email address for further information: Jonathan
Rosenberg, <jdrosen@jdrosen.net>
Intended usage: COMMON
Author/Change controller: The IETF.
8.2 URN Sub-Namespace Registration for
urn:ietf:params:xml:ns:watcherinfo
This section registers a new XML namespace, as per the guidelines in
[7].
URI: The URI for this namespace is urn:ietf:params:xml:ns:cpim-
pidf.
Registrant Contact: IETF, SIMPLE working group,
<simple@mailman.dynamicsoft.com>, Jonathan Rosenberg
<jdrosen@jdrosen.net>.
XML:
BEGIN
<?xml version="1.0"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML Basic 1.0//EN"
"http://www.w3.org/TR/xhtml-basic/xhtml-basic10.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="content-type"
content="text/html;charset=iso-8859-1"/>
<title>Watcher Information Namespace</title>
</head>
<body>
<h1>Namespace for Watcher Information</h1>
<h2>application/watcherinfo+xml</h2>
<p>See <a href="[[[URL of published RFC]]]">RFCXXXX</a>.</p>
</body>
</html>
END
9 Contributors
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The following people were part of the original design team that
developed the first version of this specification:
Dean Willis
dynamicsoft
5100 Tennyson Parkway, Suite 1200
Plano, Texas 75024
email: dwillis@dynamicsoft.com
Robert Sparks
dynamicsoft
5100 Tennyson Parkway, Suite 1200
Plano, Texas 75024
email: rsparks@dynamicsoft.com
Ben Campbell
dynamicsoft
5100 Tennyson Parkway, Suite 1200
Plano, Texas 75024
email: bcampbell@dynamicsoft.com
Henning Schulzrinne
Columbia University
M/S 0401
1214 Amsterdam Ave.
New York, NY 10027-7003
email: schulzrinne@cs.columbia.edu
Jonathan Lennox
Columbia University
M/S 0401
1214 Amsterdam Ave.
New York, NY 10027-7003
email: lennox@cs.columbia.edu
Christian Huitema
Microsoft Corporation
One Microsoft Way
Redmond, WA 98052-6399
email: huitema@microsoft.com
Bernard Aboba
Microsoft Corporation
One Microsoft Way
Redmond, WA 98052-6399
email: bernarda@microsoft.com
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David Gurle
Microsoft Corporation
One Microsoft Way
Redmond, WA 98052-6399
email: dgurle@microsoft.com
Jonathan Lennox contributed the text for the DTD and its usage that
were part of earlier versions of this specification.
10 Acknowledgements
The authors would like to thank Sean Olson, Steve Donovan, and Cullen
Jennings for their detailed comments and assistance with the XML
schema.
11 Authors Addresses
Jonathan Rosenberg
dynamicsoft
72 Eagle Rock Avenue
East Hanover, NJ 07936
email: jdrosen@dynamicsoft.com
12 Normative References
[1] A. Roach, "SIP-specific event notification," Internet Draft,
Internet Engineering Task Force, Mar. 2002. Work in progress.
[2] J. Rosenberg, "A SIP event sub-package for watcher information,"
Internet Draft, Internet Engineering Task Force, Mar. 2002. Work in
progress.
[3] S. Bradner, "Key words for use in RFCs to indicate requirement
levels," RFC 2119, Internet Engineering Task Force, Mar. 1997.
[4] W. W. W. C. (W3C), "Extensible markup language (xml) 1.0." The
XML 1.0 spec can be found at http://www.w3.org/TR/1998/REC-xml-
19980210.
[5] R. Moats, "URN syntax," RFC 2141, Internet Engineering Task
Force, May 1997.
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[6] R. Moats, "A URN namespace for IETF documents," RFC 2648,
Internet Engineering Task Force, Aug. 1999.
[7] M. Mealling, "The IANA XML registry," Internet Draft, Internet
Engineering Task Force, Nov. 2001. Work in progress.
[8] J. Rosenberg, H. Schulzrinne, et al. , "SIP: Session initiation
protocol," Internet Draft, Internet Engineering Task Force, Feb.
2002. Work in progress.
[9] M. Murata, S. S. Laurent, and D. Kohn, "XML media types," RFC
3023, Internet Engineering Task Force, Jan. 2001.
[10] J. Rosenberg et al. , "Session initiation protocol (SIP)
extensions for presence," Internet Draft, Internet Engineering Task
Force, Apr. 2002. Work in progress.
13 Informative References
[11] M. Day, J. Rosenberg, and H. Sugano, "A model for presence and
instant messaging," RFC 2778, Internet Engineering Task Force, Feb.
2000.
Full Copyright Statement
Copyright (c) The Internet Society (2002). All Rights Reserved.
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
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included on all such copies and derivative works. However, this
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The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns.
This document and the information contained herein is provided on an
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
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BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
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