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rfc:rfc4481

Network Working Group H. Schulzrinne Request for Comments: 4481 Columbia U. Category: Standards Track July 2006

                  Timed Presence Extensions to the
             Presence Information Data Format (PIDF) to
   Indicate Status Information for Past and Future Time Intervals

Status of This Memo

 This document specifies an Internet standards track protocol for the
 Internet community, and requests discussion and suggestions for
 improvements.  Please refer to the current edition of the "Internet
 Official Protocol Standards" (STD 1) for the standardization state
 and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

 Copyright (C) The Internet Society (2006).

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.

Table of Contents

 1. Introduction ....................................................2
 2. Terminology and Conventions .....................................2
 3. Timed-Status Element ............................................3
 4. Example .........................................................4
 5. The XML Schema Definition .......................................5
 6. IANA Considerations .............................................6
    6.1. URN Sub-Namespace Registration for
         'urn:ietf:params:xml:ns:pidf:timed-status' .................6
    6.2. Schema Registration for Schema
         'urn:ietf:params:xml:ns:pidf:timed-status' .................7
 7. Security Considerations .........................................7
 8. References ......................................................7
    8.1. Normative References .......................................7
    8.2. Informative References .....................................7
 Contributor's Address ..............................................8
 Acknowledgements ...................................................8

Schulzrinne Standards Track [Page 1] RFC 4481 Timed Presence July 2006

1. Introduction

 Traditionally, presence information, e.g., represented as Presence
 Information Data Format [3] (PIDF) and augmented by Rich Presence
 Information Data format [9] (RPID), 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.
 In this document, we use terms defined in RFC 2778 [7].  In
 particular, a "presentity", abbreviating presence entity, provides
 presence information to a presence service.  It is typically a
 uniquely-identified person.
 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 these 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.

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].

Schulzrinne Standards Track [Page 2] RFC 4481 Timed Presence July 2006

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 elements that
 overlap in time, 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 PIDF <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> element that covers the present time.  The PA MAY
 either discard that element 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 [8] 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.  Originators of presence
 information MUST generate time values in the <timed-status> elements
 that are fully in the past or future relative to local real
 (wallclock) time and the time information contained in the optional
 PIDF <timestamp> element.

Schulzrinne Standards Track [Page 3] RFC 4481 Timed Presence July 2006

4. Example

 An example combining PIDF and timed-status is shown below:
 <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="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>

Schulzrinne Standards Track [Page 4] RFC 4481 Timed Presence July 2006

5. The XML Schema Definition

 The XML [4] schema [5][6] 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"/>
   <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>

Schulzrinne Standards Track [Page 5] RFC 4481 Timed Presence July 2006

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
    RFC 4481 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 Status
         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="http://www.rfc-editor.org/rfc/rfc4481.txt">
            RFC4481</a>.</p>
     </body>
     </html>
    END

Schulzrinne Standards Track [Page 6] RFC 4481 Timed Presence July 2006

6.2. Schema Registration for Schema

    'urn:ietf:params:xml:ns:pidf:timed-status'
 URI:  urn:ietf:params:xml:ns:pidf:timed-status
 Registrant Contact:  IESG
 XML:  See Section 5

7. Security Considerations

 The security issues are similar to those for RPID [9].

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.
 [4]  Yergeau, F., Paoli, J., Sperberg-McQueen, C., Bray, T., and E.
      Maler, "Extensible Markup Language (XML) 1.0 (Third Edition)",
      W3C REC REC-xml-20040204, February 2004.
 [5]  Maloney, M., Beech, D., Thompson, H., and N. Mendelsohn, "XML
      Schema Part 1: Structures Second Edition", W3C REC REC-
      xmlschema-1-20041028, October 2004.
 [6]  Malhotra, A. and P. Biron, "XML Schema Part 2: Datatypes Second
      Edition", W3C REC REC-xmlschema-2-20041028, October 2004.

8.2. Informative References

 [7]  Day, M., Rosenberg, J., and H. Sugano, "A Model for Presence and
      Instant Messaging", RFC 2778, February 2000.
 [8]  Peterson, J., "A Presence-based GEOPRIV Location Object Format",
      RFC 4119, December 2005.

Schulzrinne Standards Track [Page 7] RFC 4481 Timed Presence July 2006

 [9]  Schulzrinne, H., Gurbani, V., Kyzivat, P., and J. Rosenberg,
      "RPID: Rich Presence Extensions to the Presence Information Data
      Format (PIDF)", RFC 4480, July 2006.

Contributor's Address

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

Acknowledgements

 This document is based on the discussions within the IETF SIMPLE
 working group.  Mary Barnes, Avri Doria, Miguel Garcia, Vijay
 Gurbani, Hisham Khartabil, Paul Kyzivat, Mikko Lonnfors, Yannis
 Pavlidis and Jon Peterson provided helpful comments.

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

Schulzrinne Standards Track [Page 8] RFC 4481 Timed Presence July 2006

Full Copyright Statement

 Copyright (C) The Internet Society (2006).
 This document is subject to the rights, licenses and restrictions
 contained in BCP 78, and except as set forth therein, the authors
 retain all their rights.
 This document and the information contained herein are provided on an
 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
 ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
 INCLUDING 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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Acknowledgement

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 Administrative Support Activity (IASA).

Schulzrinne Standards Track [Page 9]

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