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Copyright (C) The Internet Society (2004). All Rights Reserved.

Abstract

The Presence Information Data Format (PIDF) defines a basic XML format for presenting presence information for a presentity. The timed presence extension adds elements to PIDF that allow a presentity to declare their status for a time interval fully in the future or the past.

Table of Contents

1.  Introduction
2.  Terminology and Conventions
3.  Timed-Status Element
4.  Example
5.  The XML Schema Definition
6.  IANA Considerations
    6.1  URN Sub-Namespace Registration for 'urn:ietf:params:xml:ns:pidf:timed-status'
    6.2  Schema Registration for Schema urn:ietf:params:xml:ns:pidf:timed-status'
7.  Security Considerations
§.  Normative References
§.  Informative References
§  Author's Address
A.  Contributors
B.  Acknowledgments
§  Intellectual Property and Copyright Statements

1. Introduction

Presence information, e.g., represented as PIDFSugano, H. and S. Fujimoto, Presence Information Data Format (PIDF), May 2003.[3] and RPIDSchulzrinne, H., Gurbani, V., Kyzivat, P. and J. Rosenberg, RPID: Rich Presence: Extensions to the Presence Information Data Format (PIDF), March 2004.[4], describes the current state of the presentity. RPID also allows a presentity to indicate how long certain aspects of the status have been valid and how long they are expected to be valid, but the time range has to include the time when the presence information is published and delivered to the watcher. This restriction is necessary to avoid backwards-compatibility problems with plain PIDF implementations.

In some cases, the 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.

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 a meeting that ended an hour ago indicates that the presentity is likely in transit at the current time.

Future or past status cannot be expressed with <status> elements that use optional attributes or elements indicating such past or future time ranges. If they did, PIDF parsers would ignore those optional attributes or elements, and would not be able to distinguish current information from past or future 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 timeperiod.

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 2119Bradner, S., Key words for use in RFCs to Indicate Requirement Levels, March 1997.[1].

3. Timed-Status Element

The <timed-status> element 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, 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.

A presence agent (PA) MAY convert stored published <timed-status> tuples which are covering the present time when a notification is sent to regular PIDF tuples or it MAY simply discard them during the composition operation.

The <timed-status> element may contain any PIDF element, <basic> and <note>, as well as status extensions, such as RPIDSchulzrinne, H., Gurbani, V., Kyzivat, P. and J. Rosenberg, RPID: Rich Presence: Extensions to the Presence Information Data Format (PIDF), March 2004.[4]. However, not all elements in PIDF extensions are sensible in this context. For example, information such as contact informationSchulzrinne, H., CIPID: Contact Information in Presence Information Data Format, July 2004.[5] that does not change as a function of time is inappropriate for use with timed status.

Note that this document chooses 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.

4. Example

An example combining PIDF and timed-status is shown below:

<?xml version="1.0" encoding="UTF-8"?>
<presence xmlns="urn:ietf:params:xml:ns:pidf"
  xmlns:ts="urn:ietf:params:xml:ns:pidf:timed-status"
  entity="pres:someone@example.com">
 
  <tuple id="7c8dqui">
    <status>
      <basic>open</basic>
    </status>
    <ts:timed-status from="2003-08-15T10:20:00.000-05:00"
         until="2003-08-22T19:30:00.000-05:00">
         <basic>closed</basic>
    </ts:timed-status>
    <contact>sip:someone@example.com</contact>
  </tuple>
  <note>I'll be in Tokyo next week</note>
</presence>

5. The XML Schema Definition

The schema is shown below.

<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns="urn:ietf:params:xml:ns:pidf:timed-status"
    xmlns:pidf="urn:ietf:params:xml:ns:pidf"
    xmlns:xs="http://www.w3.org/2001/XMLSchema"
    elementFormDefault="qualified"
    attributeFormDefault="unqualified">

  <!-- 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/xml.xsd"/>

  <xs:annotation>
    <xs:documentation xml:lang="en">
      Describes timed-status tuple extensions for PIDF.
    </xs:documentation> 
  </xs:annotation>

  <xs:element name="timed-status" type="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"/>
     <xs:attribute name="until" type="xs:dateTime"/>
  </xs:complexType>
</xs:schema>

6. IANA Considerations

This document calls for IANA to register a new XML namespace URN and schema per [2]Mealling, M., The IETF XML Registry, January 2004..

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'

URI:

please assign

Registrant Contact:

IESG

XML:

See Section 5

7. Security Considerations

The security issues are similar to those for RPIDSchulzrinne, H., Gurbani, V., Kyzivat, P. and J. Rosenberg, RPID: Rich Presence: Extensions to the Presence Information Data Format (PIDF), March 2004.[4].

8. References

8.1 Normative References

8.2 Informative References

Author's Address

Appendix A. Contributors

Jonathan Rosenberg
dynamicsoft
600 Lanidex Plaza
Parsippany, NJ 07054-2711
USA
Email: jdrosen@dynamicsoft.com

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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