SIMPLE WG M. Lonnfors
Internet-Draft Nokia Research Center
Expires: July 21, 2004 E. Leppanen
H. Khartabil
Nokia
January 21, 2004
Presence Information Data format (PIDF) Extension for Partial
Presence
draft-ietf-simple-partial-pidf-format-00
Status of this Memo
This document is an Internet-Draft and is in full conformance with
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Copyright Notice
Copyright (C) The Internet Society (2004). All Rights Reserved.
Abstract
Presence Information Document Format (PIDF) specifies baseline XML
based format for describing presence information. One of the
characteristic of the PIDF is that document always needs to carry all
presence information available for the presentity. In some
environments where low bandwidth and high latency links can exist it
is often beneficial to limit the amount of information that is
transported over the network. This document introduces a new MIME
type which enables transporting of only changed parts of the PIDF
based presence information.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Structure of partial PIDF documents . . . . . . . . . . . . 4
3.1 "version" attribute . . . . . . . . . . . . . . . . . . . . 4
3.2 "state" attribute . . . . . . . . . . . . . . . . . . . . . 4
3.3 <removed> element . . . . . . . . . . . . . . . . . . . . . 4
3.3.1 <t_id> element . . . . . . . . . . . . . . . . . . . . . . . 5
4. Usage of 'application/pidf-partial+xml' . . . . . . . . . . 5
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . 5
5.1 Content-type registration for
'application/pidf-partial+xml' . . . . . . . . . . . . . . . 6
5.2 URN sub-namespace registration for
'urn:ietf:params:xml:ns:pidf-partial' . . . . . . . . . . . 6
6. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 7
7. XML Schema . . . . . . . . . . . . . . . . . . . . . . . . . 9
8. Interoperability Considerations . . . . . . . . . . . . . . 10
9. Security Considerations . . . . . . . . . . . . . . . . . . 11
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 11
Normative references . . . . . . . . . . . . . . . . . . . . 11
Informative references . . . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 12
Intellectual Property and Copyright Statements . . . . . . . 13
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1. Introduction
Presence Information Document Format (PIDF) specifies baseline XML
based format for describing presence information. One of the
characteristic of the PIDF is that document always needs to carry all
presence information available for the presentity. In some
environments where low bandwidth and high latency links can exist it
is often beneficial to limit the amount of information that is
transported over the network. This document introduces a new MIME
type which enables transporting of only changed parts of the PIDF
based presence information.
This new MIME type works in <tuple> element level so that it allows
indicating if new tuples have been added, previously received tuples
have changed, or that some tuples have been removed. These
modifications are always relative to previously received presence
information.
This document introduces a new MIME-Type 'application/
pidf-partial+xml' which is based on PIDF presence data format [4] but
is enhanced to support partial presence documents.
2. Conventions
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 [1] and
indicate requirement levels for compliant implementations.
This memo makes use of the vocabulary defined in [2]. In addition
following terms are defined:
Full presence document: Presence document which contains all presence
information that is available about the particular presentity to
the watcher in question. The full presence document can be
represented by MIME type 'application/pidf+xml' and 'application/
partial-pidf+xml' when the "state" attribute is set to value
"full".
Partial presence document: Document which represents only a fragment
of the full presence document. Partial presence documents can only
be understood in the context of the full presence document i.e. a
partial presence document modifies the local copy of the full
presence document. MIME type 'application/partial-pidf+xml"
document represent partial presence document when the "state"
attribute contains value "partial".
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3. Structure of partial PIDF documents
The mechanism for implementing the partial PIDF consists of defining
a new MIME type. The new MIME type is named as 'application/
pidf-partial+xml'. It is similar to PIDF [4] except that it adds new
XML attributes to the <presence> element in order to enable the
partial PIDF. The new XML attributes are "version" and "state". The
new MIME type also introduces a new XML element called "removed".
Implementations using this document format must follow guidelines
specified in [4] i.e. XML document MUST be well formed and SHOULD be
valid. Presence documents MUST be based on XML 1.0 and MUST be
encoded using UTF-8. This specification makes use of XML namespaces
for identifying presence 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:pidf-partial
3.1 "version" attribute
Every presence document compliant with this specification MUST
include the "version" attribute in <presence> element.
The "version" attribute is a sequence number that is progressively
incremented between subsequent documents i.e. a more resent document
has higher "version" value than a previously received one. The
recipient of the document can use "version" attribute to properly
order received documents. Version start at 0, and is incremented by
one for each new document. Versions MUST be representable using a 32
bit integer.
3.2 "state" attribute
Every presence document compliant with this specification MUST
include "state" attribute in <presence> element. It can have values:
'full' or 'partial'.
The "state" attribute indicates the nature of the presence
information included in the document, whether it contains full or
partial presence document corresponding to the cases when the full
presence information or only changed parts of the presence
information are delivered. The use of these attributes is similar to
the watcher information template package [8].
3.3 <removed> element
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This element is used to carry a list of tuples which have been
removed. The <removed> element contains any number of <t_id> elements
each of which has the value of the "id" attribute of the tuple which
has been removed.
3.3.1 <t_id> element
If document contains <removed> element it MUST contain at least one
<t_id> element. This element contains the tuple ID as indicated by
the "id" attribute of the tuple that has been removed.
4. Usage of 'application/pidf-partial+xml'
Presence documents which are compliant with 'application/
pidf-partial+xml' MIME type MUST be constructed according to
following logic:
o If the presence document represents full presence document the
"state" attribute MUST be set to value "full". In this case the
rest of the presence document is contructed as defined in PIDF
[4].
o If the presence document represents partial presence document the
"state" attribute MUST be set to value "partial". The presence
document MUST only contain tuples which have changed compared to
last time the presence document was delivered i.e. it must contain
new tuples and modified tuples. Tuples MUST be included completely
i.e. including only a fragment of the tuple is not allowed. Tuples
which have not changed MUST NOT be included. If some tuples have
been removed "id" attributes of those tuples must be listed under
<removed> element.
In the scope of this document the partial presence documents apply
only to the <tuple> elements and everything what is contained inside
those elements i.e. tuples are considered to be atomic data elements.
All other elements defined in PIDF [4] which are child elements to
the <presence> element (only the <note> element has been defined)
MUST be included in every presence document.
5. IANA Considerations
This memo calls for IANA to:
o register a new XML namespace URN per [7].
o register new a content type 'application/pidf-partial+xml' per
RFC2048 [11].
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5.1 Content-type registration for 'application/pidf-partial+xml'
MIME media type name: application
MIME subtype name: pidf-partial+xml
Mandatory parameters: none
Optional parameters: charset
Indicates the character encoding of enclosed XML. Default is
UTF-8.
Encoding considerations:
Uses XML, which can employ 8-bit characters, depending on the
character encoding used. See RFC 3023 [9], section 3.2.
Security considerations:
This content type is designed to carry presence data, which may be
considered private information. Appropriate precautions should be
adopted to limit disclosure of this information.
Interoperability considerations: none
Published specification: [[[RFCXXXX]]] this document
Applications which use this media type: SIP-based presence systems
Additional information:
Magic Number: None
File Extension: .xml
Macintosh file type code: "TEXT"
Personal and email address for further information: Mikko
Lonnfors, mikko.lonnfors@nokia.com
Intended usage: LIMITED USE
Author/Change controller:
This specification is a work item of the IETF SIMPLE working
group, with mailing list address <simple@ietf.org>.
5.2 URN sub-namespace registration for
'urn:ietf:params:xml:ns:pidf-partial'
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URI:
urn:ietf:params:xml:ns:pidf-partial
Description:
This is the XML namespace for XML elements defined by
[[[RFCXXXX]]] to describe the 'application/pidf-partial+xml'
content type for partial PIDF.
Registrant Contact:
IETF, SIMPLE working group, <simple@ietf.org>
Mikko Lonnfors, <mikko.lonnfors@nokia.com>
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>PIDF extension for partial PIDF</title>
</head>
<body>
<h1>Namespace for PIDF extension for partial
notifications</h1>
<h2>application/pidf-partial+xml</h2>
<p>See <a href="[[[URL of published RFC]]]">RFCXXXX</a>.</p>
</body>
</html>
END
6. Examples
'application/pidf-partial+xml' document which contains full state
information:
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<?xml version="1.0" encoding="UTF-8"?>
<pidf-part:presence xmlns="urn:ietf:params:xml:ns:pidf"
xmlns:pidf-part="urn:ietf:params:xml:ns:pidf-partial"
entity="pres:someone@example.com" pidf:part:version="1"
pidf-part:state="full">
<tuple id="sg89ae">
<status><basic>open</basic>
</status>
<contact priority="0.8">tel:09012345678
</contact>
</tuple>
<tuple id="cg231jcr">
<status><basic>open</basic>
</status>
<contact priority="1.0">
im:pep@example.com</contact>
</tuple>
<tuple id="r1230d">
<status><basic>closed</basic>
</status>
<contact priority="0.9">
sip:pep@example.com</contact>
</tuple>
</presence>
New 'application/pidf-partial+xml' document which contains partial
state information:
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<?xml version="1.0" encoding="UTF-8"?>
<pidf-part:presence xmlns="urn:ietf:params:xml:ns:pidf"
xmlns:pidf-part="urn:ietf:params:xml:ns:pidf-partial"
entity="pres:someone@example.com" pidf-part:version="2"
pidf-part:state="partial">
<pidf-part:removed><pidf-part:t_id>r1230d</pidf-part:t_id>
</pidf-part:removed>
<tuple id="cg231jcr">
<status><basic>closed</basic>
</status>
<contact priority="1.0">
im:pep@example.com</contact>
<note xml:lang="en">This is an update of existing
tuple sent in previous notification</note>
</tuple>
<tuple id="wsqw798jcr">
<status><basic>open</basic>
</status>
<contact priority="0.4">
im:mac@hut.com</contact>
<note xml:lang="en">This is a completely new
tuple not sent in previous notification</note>
</tuple>
</presence>
7. XML Schema
The XML schema for the 'application/pidf-partial+xml' data format.
<?xml version="1.0" encoding="UTF-8"?>
<xs:schema targetNamespace="urn:ietf:params:xml:ns:pidf-partial"
xmlns:xs="http://www.w3.org/2001/XMLSchema"
xmlns:pidf="urn:ietf:params:xml:ns:pidf"
xmlns:tns="urn:ietf:params:xml:ns:pidf-partial"
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:import namespace="urn:ietf:params:xml:ns:pidf"/>
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<xs:element name="presence"
type="tns:partial-presence"/>
<xs:complexType name="partial-presence">
<xs:complexContent>
<xs:extension base="pidf:presence">
<xs:sequence>
<xs:element name="removed"
type="tns:removed_tuple"
minOccurs="0"/>
</xs:sequence>
<xs:attribute name="entity"
type="xs:anyURI"
use="required"/>
<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>
</xs:simpleType>
</xs:attribute>
</xs:extension>
</xs:complexContent>
</xs:complexType>
<xs:complexType name="removed_tuple">
<xs:sequence>
<xs:element name="t_id"
type="xs:ID"
maxOccurs="unbounded"/>
</xs:sequence>
</xs:complexType>
</xs:schema>
8. Interoperability Considerations
This specification is not by default compliant with work done in IMPP
working group. This means that other systems compliant with CPP [10]
will not be by default able to use this specification. However, this
will not cause any interoperability problems because all endpoints
and gateways must support the default MIME type (application/
pidf+xml) regardless if they support this specification. Thus if a
gateway or another end point does not understand this specification
it will not be used.
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Other CPP compliant (other than SIP based) systems can also support
this specification if they have a mechanism to indicate support for
it. If they do it is possible to build a gateway which will preserves
the end to end integrity with usage of partial PIDF.
9. Security Considerations
Presence information may contain highly sensitive information about
the presentities. The protocol used to distribute it SHOULD ensure
privacy, message integrity and authentication. Furthermore, the
protocol should provide access controls which restrict who can see
who else's presence information.
10. Acknowledgements
The authors would like to thank Jose Costa-Requena, Jyrki Aarnos,
Jonathan Rosenberg, Dean Willis, Kriztian Kiss for their valuable
comments and contributions.
Normative references
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
[2] Day, M., Rosenberg, J. and H. Sugano, "A Model for Presence and
Instant Messaging", RFC 2778, February 2000.
[3] Rosenberg, J., "SIP Extensions for Presence",
draft-ietf-simple-presence-10 (work in progress), January 2003.
[4] Sugano, H., "CPIM presence information data format",
draft-ietf-impp-cpim-pidf-08 (work in progress), May 2003.
[5] Moats, R., "URN syntax", RFC 2141, May 1997.
[6] Moats, R., "A URN namespace for IETF documents", RFC 2648, Aug.
1999.
Informative references
[7] Mealling, M., "The IETF XML Registry",
draft-mealling-iana-xmlns-registry-05 (work in progress), June
2002.
[8] 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.
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[9] Murata, M., "XML media types", RFC 3023, January 2001.
[10] Crocker, D. and J. Peterson, "Common Profile for Presence
(CPP)", draft-ietf-impp-pres-02.txt (work in progress).
[11] Freed, N., Klensin, J. and J. Postel, "Multipurpose Internet
Mail Extensions (MIME) Part Four: Registration Procedures", RFC
2048, November 1996.
Authors' Addresses
Mikko Lonnfors
Nokia Research Center
Itamerenkatu 11-13 00180
Helsinki
Finland
Phone: +358 71 8008000
EMail: mikko.lonnfors@nokia.com
Eva Leppanen
Nokia
P.O BOX 785
Tampere
Finland
Phone: +358 7180 77066
EMail: eva-maria.leppanen@nokia.com
Hisham Khartabil
Nokia
P.O. Box 321
Helsinki
Finland
Phone: +358 7180 76161
EMail: hisham.khartabil@nokia.com
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