SIMPLE H. Schulzrinne
Internet-Draft Columbia U.
Expires: December 28, 2005 June 26, 2005
Timed Presence Extensions to the Presence Information Data Format (PIDF)
to Indicate Status Information for Past and Future Time Intervals
draft-ietf-simple-future-04
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Copyright (C) The Internet Society (2005).
Abstract
The Presence Information Data Format (PIDF) defines a basic XML
format for presenting presence information for a presentity. This
document extends PIDF, adding a timed status extension (<timed-
status> element) that allows a presentity to declare its status for a
time interval fully in the future or the past.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology and Conventions . . . . . . . . . . . . . . . . . 4
3. Timed-Status Element . . . . . . . . . . . . . . . . . . . . . 5
4. Example . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
5. The XML Schema Definition . . . . . . . . . . . . . . . . . . 7
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
6.1 URN Sub-Namespace Registration for
'urn:ietf:params:xml:ns:pidf:timed-status' . . . . . . . . 8
6.2 Schema Registration for Schema
urn:ietf:params:xml:ns:pidf:timed-status' . . . . . . . . 8
7. Security Considerations . . . . . . . . . . . . . . . . . . . 10
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 11
8.1 Normative References . . . . . . . . . . . . . . . . . . . 11
8.2 Informative References . . . . . . . . . . . . . . . . . . 11
Author's Address . . . . . . . . . . . . . . . . . . . . . . . 11
A. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 12
B. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 13
Intellectual Property and Copyright Statements . . . . . . . . 14
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1. Introduction
Traditionally, presence information, e.g., represented as PIDF [3]
and RPID [6], describes the current state of the presentity.
However, a watcher can better plan communications if it knows about
the presentity's future plans. For example, if a watcher knows that
the presentity is about to travel, it might place a phone call
earlier.
RPID already allows a presentity to indicate the period when a
particular aspect of its presence is valid. However, the <status>
element in the PIDF <tuple> does not have this facility, so that it
is not possible to indicate that a presentity will be OPEN or CLOSED
in the future, for example.
It is also occasionally useful to represent past information since it
may be the only known presence information; it may give watchers an
indication of the current status. For example, indicating that the
presentity was at an off-site meeting that ended an hour ago
indicates that the presentity is likely in transit at the current
time.
It is unfortunately not possible to simply add time range attributes
to the PIDF <status> element, as PIDF parsers without this capability
would ignore thes attributes and thus not be able to distinguish
current from future presence status information.
This document defines the <timed-status> element that describes the
status of a presentity that is either no longer valid or covers some
future time period.
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2. Terminology and Conventions
The key words MUST, MUST NOT, REQUIRED, SHOULD, SHOULD NOT,
RECOMMENDED, MAY, and OPTIONAL in this document are to be interpreted
as described in BCP 14, RFC 2119 [1].
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3. Timed-Status Element
The <timed-status> element is a child of the <tuple> element and MUST
NOT appear as a child of a PIDF <status> element or another <timed-
status> element. More than one such element MAY appear within a PIDF
<tuple> element.
Sources of <timed-status> information should avoid overlapping
elements, but since overlapping appointments are common in calendars,
for example, receivers MUST be able to render such overlapping
<timed-status> indications.
The <timed-status> element MUST be qualified with the 'from'
attribute and MAY be qualified with an 'until' attribute to describe
the time when the status assumed this value and the time until which
this element is expected to be valid. If the 'until' attribute is
missing, the information is assumed valid until the tuple is
explicitly overridden or expires as defined by the publication
mechanism used. The time range MUST NOT encompass the present time,
i.e., the <timestamp> value, as that would provide an unnecessary and
confusing alternate mechanism to describe presence. Thus, the 'from'
attribute for tuples without an 'until' attribute MUST refer to the
future.
During composition, a presence agent (PA) may encounter a stored
<timed-status> elements that covers the present time. The PA MAY
either discard those elements or MAY convert it to a regular <status>
element if it considers that information more credible.
The <timed-status> element may contain the <basic> and <note>
elements, as well as any other element that is appropriate as a PIDF
<status> extension and that has a limited validity period. Examples
include the PIDF-LO [5] extensions for location objects.
This extension chose absolute rather than relative times, since
relative times would be too hard to keep properly updated when
spacing notifications, for example. Implementations SHOULD ascertain
whether the time values in the <timed-status> elements are plausible,
for example, by checking whether the time stamp in a notification
protocol message corresponds to local time and by making sure that
they are fully in the past or future, both relative to real time and
the time contained in the optional PIDF <timestamp> element.
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4. Example
An example combining PIDF and timed-status is shown below:
<presence xmlns="urn:ietf:params:xml:ns:pidf"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:ts="urn:ietf:params:xml:ns:pidf:timed-status"
xsi:schemaLocation="urn:ietf:params:xml:ns:pidf pidf.xsd
urn:ietf:params:xml:ns:pidf:data-model data-model.xsd
urn:ietf:params:xml:ns:pidf:timed-status timed-status.xsd"
entity="pres:someone@example.com">
<tuple id="c8dqui">
<status>
<basic>open</basic>
</status>
<ts:timed-status from="2005-08-15T10:20:00.000-05:00"
until="2005-08-22T19:30:00.000-05:00">
<ts:basic>closed</ts:basic>
</ts:timed-status>
<contact>sip:someone@example.com</contact>
</tuple>
<note>I'll be in Tokyo next week</note>
</presence>
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5. The XML Schema Definition
The schema is shown below.
<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:ts="urn:ietf:params:xml:ns:pidf:timed-status"
xmlns:pidf="urn:ietf:params:xml:ns:pidf"
xmlns:xs="http://www.w3.org/2001/XMLSchema"
targetNamespace="urn:ietf:params:xml:ns:pidf:timed-status"
elementFormDefault="qualified" attributeFormDefault="unqualified">
<xs:import namespace="urn:ietf:params:xml:ns:pidf"
schemaLocation="pidf.xsd"/>
<xs:annotation>
<xs:documentation>
Describes timed-status tuple extensions for PIDF.
</xs:documentation>
</xs:annotation>
<xs:element name="timed-status" type="ts:timed-status"/>
<xs:complexType name="timed-status">
<xs:sequence>
<xs:element name="basic" type="pidf:basic" minOccurs="0"/>
<xs:element name="note" type="pidf:note" minOccurs="0"/>
<xs:any namespace="##other" processContents="lax" minOccurs="0"
maxOccurs="unbounded"/>
</xs:sequence>
<xs:attribute name="from" type="xs:dateTime" use="required"/>
<xs:attribute name="until" type="xs:dateTime"/>
</xs:complexType>
</xs:schema>
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6. IANA Considerations
This document calls for IANA to register a new XML namespace URN and
schema per [2].
6.1 URN Sub-Namespace Registration for
'urn:ietf:params:xml:ns:pidf:timed-status'
URI: urn:ietf:params:xml:ns:pidf:timed-status
Description: This is the XML namespace for XML elements defined by
RFCXXXX to describe timed-status presence information extensions
for the status element in the PIDF presence document format in the
application/pidf+xml content type.
Registrant Contact: IETF, SIMPLE working group, simple@ietf.org;
Henning Schulzrinne, hgs@cs.columbia.edu
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>Timed Presence Extensions to the Presence
Information Data Format (PIDF) to Indicate Presence
Information for Past and Future Time Intervals</title>
</head>
<body>
<h1>Namespace for timed-status presence extension</h1>
<h2>urn:ietf:params:xml:ns:pidf:timed-status</h2>
<p>See <a href="URL of published RFC">RFCXXXX</a>.</p>
</body>
</html>
END
6.2 Schema Registration for Schema
urn:ietf:params:xml:ns:pidf:timed-status'
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URI: please assign
Registrant Contact: IESG
XML: See Section 5
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7. Security Considerations
The security issues are similar to those for RPID [6].
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8. References
8.1 Normative References
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
[2] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
January 2004.
[3] Sugano, H., Fujimoto, S., Klyne, G., Bateman, A., Carr, W., and
J. Peterson, "Presence Information Data Format (PIDF)",
RFC 3863, August 2004.
8.2 Informative References
[4] Rosenberg, J., "A Data Model for Presence",
draft-ietf-simple-presence-data-model-02 (work in progress),
February 2005.
[5] Peterson, J., "A Presence-based GEOPRIV Location Object Format",
draft-ietf-geopriv-pidf-lo-03 (work in progress),
September 2004.
[6] Schulzrinne, H., "RPID: Rich Presence Extensions to the Presence
Information Data Format (PIDF)", draft-ietf-simple-rpid-06
(work in progress), June 2005.
[7] Schulzrinne, H., "CIPID: Contact Information in Presence
Information Data Format", draft-ietf-simple-cipid-04 (work in
progress), June 2005.
Author's Address
Henning Schulzrinne
Columbia University
Department of Computer Science
450 Computer Science Building
New York, NY 10027
US
Phone: +1 212 939 7004
Email: hgs+simple@cs.columbia.edu
URI: http://www.cs.columbia.edu
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Appendix A. Contributors
Jonathan Rosenberg
dynamicsoft
600 Lanidex Plaza
Parsippany, NJ 07054-2711
USA
Email: jdrosen@dynamicsoft.com
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Appendix B. Acknowledgments
This document is based on the discussions within the IETF SIMPLE
working group. Mary Barnes, Miguel Garcia, Vijay Gurbani, Hisham
Khartabil, Paul Kyzivat, Mikko Lonnfors, Yannis Pavlidis and Jon
Peterson provided helpful comments.
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