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Versions: (draft-lonnfors-simple-prescaps-ext) 00 01 02 03 04 05 06 07 08 09 10 RFC 5196

SIMPLE WG                                                    M. Lonnfors
Internet-Draft                                                   K. Kiss
Intended status: Standards Track                                   Nokia
Expires: November 15, 2008                                  May 14, 2008


  Session Initiation Protocol (SIP) User Agent Capability Extension to
                Presence Information Data Format (PIDF)
                   draft-ietf-simple-prescaps-ext-10

Status of this Memo

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   This Internet-Draft will expire on November 15, 2008.

Abstract

   Presence Information Data Format (PIDF) defines a common presence
   data format for Common Profile for Presence (CPP) compliant Presence
   protocols.  This memo defines an extension to represent SIP User
   Agent capabilities in the Presence Information Document Format (PIDF)
   compliant presence documents.









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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
     1.1.  Motivation . . . . . . . . . . . . . . . . . . . . . . . .  4
     1.2.  Scope  . . . . . . . . . . . . . . . . . . . . . . . . . .  5
   2.  Conventions  . . . . . . . . . . . . . . . . . . . . . . . . .  5
   3.  Extension for "Indicating User Agent Capabilities in the
       Session Initiation Protocol (SIP)" in PIDF documents . . . . .  5
     3.1.  Overview of operation  . . . . . . . . . . . . . . . . . .  5
     3.2.  Service capabilities . . . . . . . . . . . . . . . . . . .  6
       3.2.1.  <servcaps> element . . . . . . . . . . . . . . . . . .  6
       3.2.2.  <audio> element  . . . . . . . . . . . . . . . . . . .  6
       3.2.3.  <application> element  . . . . . . . . . . . . . . . .  6
       3.2.4.  <data> element . . . . . . . . . . . . . . . . . . . .  7
       3.2.5.  <control> element  . . . . . . . . . . . . . . . . . .  7
       3.2.6.  <video> element  . . . . . . . . . . . . . . . . . . .  7
       3.2.7.  <text> element . . . . . . . . . . . . . . . . . . . .  7
       3.2.8.  <message> element  . . . . . . . . . . . . . . . . . .  8
       3.2.9.  <type> element . . . . . . . . . . . . . . . . . . . .  8
       3.2.10. <automata> element . . . . . . . . . . . . . . . . . .  8
       3.2.11. <class> element  . . . . . . . . . . . . . . . . . . .  8
       3.2.12. <duplex> element . . . . . . . . . . . . . . . . . . .  9
       3.2.13. <description> element  . . . . . . . . . . . . . . . .  9
       3.2.14. <event-packages> element . . . . . . . . . . . . . . . 10
       3.2.15. <priority> element . . . . . . . . . . . . . . . . . . 10
       3.2.16. <methods> element  . . . . . . . . . . . . . . . . . . 11
       3.2.17. <extensions> element . . . . . . . . . . . . . . . . . 11
       3.2.18. <schemes> element  . . . . . . . . . . . . . . . . . . 12
       3.2.19. <actor> element  . . . . . . . . . . . . . . . . . . . 12
       3.2.20. <isfocus> element  . . . . . . . . . . . . . . . . . . 13
       3.2.21. <languages> element  . . . . . . . . . . . . . . . . . 13
     3.3.  Device capabilities  . . . . . . . . . . . . . . . . . . . 14
       3.3.1.  <devcaps> element  . . . . . . . . . . . . . . . . . . 14
       3.3.2.  <mobility> element . . . . . . . . . . . . . . . . . . 14
       3.3.3.  <description> element  . . . . . . . . . . . . . . . . 15
   4.  Usage guidelines . . . . . . . . . . . . . . . . . . . . . . . 15
     4.1.  Use of <supported> and <notsupported> elements . . . . . . 16
   5.  Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
   6.  XML schema definitions . . . . . . . . . . . . . . . . . . . . 18
   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 26
     7.1.  URN sub-namespace registration for
           'urn:ietf:params:xml:ns:pidf:caps' . . . . . . . . . . . . 26
   8.  Security Considerations  . . . . . . . . . . . . . . . . . . . 27
   9.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 27
   10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 28
     10.1. Normative references . . . . . . . . . . . . . . . . . . . 28
     10.2. Informative references . . . . . . . . . . . . . . . . . . 28
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 29



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   Intellectual Property and Copyright Statements . . . . . . . . . . 30


















































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1.  Introduction

   Common Profile for Presence (CPP) [RFC3859] and Common Profile for
   Instant Messaging (CPIM) [RFC3860] define common operations and
   formats which all presence and instant messaging services must agree
   upon so that basic interoperability would be possible.  The actual
   base format for the presence is defined in the Presence Information
   Document Format (PIDF) [RFC3863].  The PIDF has been designed to
   reduce the need for gatewaying and to allow end-to-end security of
   presence data.  It has taken a very minimalistic approach to support
   such operations.  In order to make the PIDF usable by different
   presence applications, these applications usually must extend the
   basic PIDF by standard XML mechanisms as defined in PIDF [RFC3863].

   The aim of this memo is to introduce a SIP specific extension
   mechanism to the PIDF that conveys the same SIP media feature tags as
   described in [RFC3840].  With this extension presence applications
   based on SIP can have richer and more usable presence data compared
   to the baseline PIDF.

1.1.  Motivation

   The PIDF [RFC3863] defines a <contact> element which may appear once
   inside every <tuple> element.  The content of the <contact> element
   encodes the CONTACT ADDRESS and CONTACT MEANS as defined in
   [RFC2778].  The <contact> element is defined to be a URI of any
   scheme.  In some implementations the URI scheme can uniquely identify
   the service the tuple intends to describe (e.g. im: URI scheme
   usually represents Instant Messaging service).  However, this may not
   be the case in all implementations.  For example in SIP, a SIP URI
   scheme can represent different kinds of services.  A SIP URI scheme
   can be used to contact voice services, video services, or messaging
   services.  If it is not known by other means, it might be hard for
   applications processing the presence information document containing
   only a SIP URI contact addresses to know what particular service the
   tuple intends to describe.  Also watchers receiving presence
   information would probably benefit for getting more descriptive
   information about what particular communication means or services are
   supported by the presentity.

   The User Agent Capabilities extension [RFC3840] defines a set of
   extensions which allow user agents to express preferences about
   request handling in SIP servers.  The same information can provide
   value also to presence watchers so that they can make more rational
   decisions on how a presentity should be contacted if a presence
   document contained similar information.





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1.2.  Scope

   This document defines PIDF extensions which enable SIP presence
   implementations to utilize User Agent Capabilities [RFC3840] within
   presence documents.

   This extension does not replace media negotiation mechanisms defined
   for SIP (e.g.  SDP [RFC4566]).  This extension is only aimed for
   presentities to give watchers hints about the presentity's
   preferences, willingness and capabilities to communicate before
   watchers initiate a communication with the presentity.


2.  Conventions

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

   This memo makes use of the vocabulary defined in [RFC2778], and in
   [RFC3863].


3.  Extension for "Indicating User Agent Capabilities in the Session
    Initiation Protocol (SIP)" in PIDF documents

   This section presents all extension documents, their elements, their
   values, and semantics.  This section also describes how this
   extension can be further extended.

   This extension is intended to be used within a PIDF [RFC3863] and
   that particular usage is described here.  This extension may also be
   used with other XML documents if appropriate.

3.1.  Overview of operation

   This document defines how the features presented in [RFC3840] can be
   provided as a part of presence data.  Additionally, this memo
   includes the "type" feature tag [RFC2913], "message" media type
   feature tag [RFC4569] and the "language" feature tag [RFC4646]
   definitions.  Bringing these features in the PIDF means mapping them
   to an XML formatted structure.

   The presence data model [RFC4479] defines presence data consisting of
   three types of data elements: person, service, and device.  This memo
   follows this model so that one XML document is defined to describe
   device capabilities and another one to describe service capabilities.




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   The namespace URIs for elements defined by this document are URNs
   using the namespace identifier 'ietf' defined by [RFC2648] and
   extended by [RFC3688].

   When these extension namespaces are congregated with the PIDF
   document, the combined document MUST follow the same general
   formatting rules as specified in Section 4.1 of [RFC3863].

3.2.  Service capabilities

   Elements belonging to service capabilities are used to describe
   dynamic characteristics of a service.  These capabilities are
   enclosed within the <servcaps> element which SHOULD be located in
   PIDF document as a child element of urn:ietf:params:xml:ns:pidf
   namespace <tuple> [RFC3863] element.

   Namespace identifier for these elements is:

   urn:ietf:params:xml:ns:pidf:caps

3.2.1.  <servcaps> element

   The root element of service capabilities is <servcaps>.  The root
   element has to be always present.  This element can contain following
   elements: <audio>, <application>, <control>, <video>, <text>,
   <message>, <type>, <automata>, <class>, <duplex>, <description>,
   <event-packages>, <priority>, <methods>, <extensions>, <schemes>,
   <actor>, <isfocus>, and <languages> followed by any number of
   optional extension elements from other namespaces.

   A <servcaps> element can contain any number of optional extension
   attributes from other namespaces.

3.2.2.  <audio> element

   The <audio> element indicates that the service supports audio as a
   streaming media type as defined in [RFC3840].

   The <audio> element is a boolean type and does not have any
   attributes.  The value 'true' indicates that service supports audio
   media type and the value 'false' indicates that service does not
   support audio media type.

3.2.3.  <application> element

   The <application> element indicates that the service supports
   application as a streaming media type as defined in [RFC3840].




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   The <application> element is a boolean type and does not have any
   attributes.  The value 'true' indicates that service supports
   application media type and the value 'false' indicates that service
   does not support application media type.

3.2.4.  <data> element

   The <data> element indicates that the service supports data as a
   streaming media type as defined in [RFC3840].

   The <data> element is a boolean type and does not have any
   attributes.  The value 'true' indicates that service supports data
   media type and the value 'false' indicates that service does not
   support data media type.

3.2.5.  <control> element

   The <control> element indicates that the service supports control as
   a streaming media type as defined in [RFC3840].

   The <control> element is a boolean type and does not have any
   attributes.  The value 'true' indicates that service supports control
   media type and the value 'false' indicates that service does not
   support control media type.

3.2.6.  <video> element

   The <video> element indicates that the service supports video as a
   streaming media type as defined in [RFC3840].

   The <video> element is a boolean type and does not have any
   attributes.  The value 'true' indicates that service supports video
   media type and the value 'false' indicates that service does not
   support video media type.

3.2.7.  <text> element

   The <text> element indicates that the service supports text as a
   streaming media type as defined in [RFC3840].

   The <text> element is a boolean type and does not have any
   attributes. the value 'true' indicates that service supports text
   media type and the value 'false' indicates that service does not
   support text media type.







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3.2.8.  <message> element

   The <message> element indicates that the service supports messaging
   as a streaming media type as defined in [RFC4569].

   The <message> element is a boolean type and does not have any
   attributes.  The value 'true' indicates that service supports message
   media type and the value 'false' indicates that service does not
   support message media type.

3.2.9.  <type> element

   The <type> element indicates a MIME media content type (i.e. that
   appears in a 'Content-type:' header of the corresponding MIME-
   formatted data) as defined in [RFC2913].

   The <type> element is a string type and does not have any attributes.
   It MUST be a string of the form "type/subtype", where 'type' and
   'subtype' are defined by the MIME specification [RFC2045].  Only
   lower-case letters SHOULD be used.

3.2.10.  <automata> element

   The <automata> element indicates whether the service represents an
   automaton (such as a voicemail server, conference server, or
   recording device) or a human as defined in [RFC3840].

   The <automata> element is a boolean type and does not have any
   attributes.  The value 'true' indicates that the service represents
   an automaton and the value 'false' indicates that it represents a
   human.

3.2.11.  <class> element

   The <class> element indicates the setting, business or personal, in
   which a communications service is used as defined in [RFC3840].

   The <class> element can contain two elements: <supported> and
   <notsupported>.  Classes that are supported by the service can be
   listed under <supported> element and classes that are not supported
   by the service can be listed under <notsupported> element.

   <supported> and <notsupported> elements can contain <business> and
   <personal> elements followed by any number of optional extension
   elements from other namespaces.  The semantics of business and
   personal are defined in [RFC3840] as:





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   o  <business>: The service is used for business communications.

   o  <personal>: The service is used for personal communications.

   Any value that is registered with IANA for the SIP Media Feature Tag
   Registration Tree as a sip.class media feature tag can be used as a
   value of an extension element.  If the appropriate value is not
   registered it SHOULD be registered as defined in [RFC3840].

3.2.12.  <duplex> element

   The <duplex> element lists whether a communications service can
   simultaneously send and receive media ("full"), alternate between
   sending and receiving ("half"), only receive ("receive-only") or only
   send ("send-only") as defined in [RFC3840].

   The <duplex> element can contain two elements: <supported> and
   <notsupported>.  Duplex modes that are supported by the service can
   be listed under <supported> element and duplex modes that are not
   supported by the service can be listed under <notsupported> element.

   <supported> and <notsupported> elements can contain <full>, <half>,
   <receive-only> and <send-only> elements followed by any number of
   optional extension elements from other namespaces.  The semantics of
   these elements are defined in [RFC3840] as:

   o  <full>: The service can simultaneously send and receive media.

   o  <half>: The service can alternate between sending and receiving
      media.

   o  <receive-only>: The service can only receive media.

   o  <send-only>: The service can only send media.

   Any value that is registered with IANA for the SIP Media Feature Tag
   Registration Tree as a sip.class media feature tag can be used as a
   value of an extension element.  If the appropriate value is not
   registered it SHOULD be registered as defined in [RFC3840].

3.2.13.  <description> element

   The <description> element provides a textual description of the
   service as defined in [RFC3840].

   The <description> element is of string type and does not have any
   attributes.




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   The <description> element SHOULD be labeled with the 'xml:lang'
   attribute to indicate its language and script.  The specification
   allows multiple occurrences of this elements so that the presentity
   can convey <description> elements in multiple scripts and languages.
   If no 'xml:lang' attribute is provided, the default value is
   "i-default" as defined in [RFC2277].

3.2.14.  <event-packages> element

   The <event-packages> element lists the event packages supported by a
   service.

   The <event-packages> element can contain two elements: <supported>
   and <notsupported>.  Event packages that are supported by the service
   can be listed under <supported> element and event packages that are
   not supported by the service can be listed under <notsupported>
   element.

   The <supported> and <notsupported> elements can contain any values
   from the IANA SIP event types namespace registry followed by any
   number of optional extension elements from other namespaces.  As of
   today the IANA SIP event types namespace registry includes the
   following packages: <conference>, <dialog>, <kpml>, <message-
   summary>, <poc-settings>, <presence>, <reg>, <refer>, <Siemens-RTP-
   Stats>, <spirits-INDPs>, <spirits-user-prof> and <winfo>.

3.2.15.  <priority> element

   The <priority> element indicates the call priorities the service is
   willing to handle as defined in [RFC3840].

   The <priority> element can contain two elements: <supported> and
   <notsupported>.  Priority values that are supported by the service
   can be listed under <supported> element and priority values that are
   not supported by the service can be listed under <notsupported>
   element.

   The <supported> and <notsupported> elements can contain any number of
   <lowerthan>, <higherthan>, <equals> and <range> elements followed by
   any number of optional extension elements from other namespaces.

3.2.15.1.  <lowerthan> element

   The <lowerthan> element has a single attribute called "maxvalue".
   The "maxvalue" attribute is used to give the highest priority value
   that the service is willing to support.  All values equal and below
   that value are supported.




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3.2.15.2.  <higherthan> element

   The <higherthan> element has a single attribute called "minvalue".
   The "minvalue" attribute is used to give the lowest priority value
   that the service is willing to support.  All values equal and above
   that value are supported.

3.2.15.3.  <equals> element

   The <equals> element is used to indicate the exact priority value
   that the service is willing to handle.  The <equals> element has a
   single attribute called "value".  The "value" attribute is used to
   indicate the exact supported priority value.

3.2.15.4.  <range> element

   The <range> element is used to indicate the priority range that the
   service is willing to handle.  The <range> element has two attributes
   called "min" and "max".  Value of the "min" attribute indicates
   lowest priority value supported by the service and the value of the
   "max" attribute indicates the highest priority value supported by the
   service.

3.2.16.  <methods> element

   The <methods> element indicates the SIP methods supported by a
   service.  In this case, "supported" means that the service can
   receive requests with this method.  In that sense, it has the same
   connotation as the Allow header field as defined in [RFC3840].

   The <methods> element can contain two elements: <supported> and
   <notsupported>.  Methods that are supported by the service can be
   listed under <supported> element and methods that are not supported
   by the service can be listed under <notsupported> element.

   The <supported> and <notsupported> elements can contain <ACK>, <BYE>,
   <CANCEL>, <INFO>, <INVITE>, <MESSAGE>, <NOTIFY>, <OPTIONS>, <PRACK>,
   <PUBLISH>, <REFER>, <REGISTER>, <SUBSCRIBE>, and <UPDATE> elements
   followed by any number of optional extension elements from other
   namespaces.

   Any value that is registered with IANA for the SIP methods namespace
   registry can be used as a value of an extension element.

3.2.17.  <extensions> element

   The <extensions> element is a list of SIP extensions (each of which
   is defined by an option-tag registered with IANA) that are understood



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   by the service.  Understood, in this context, means that the option
   tag would be included in a Supported header field in a request as
   defined in [RFC3840].

   The <extensions> element can contain two elements: <supported> and
   <notsupported>.  Extensions that are supported by the service can be
   listed under <supported> element and extensions that are not
   supported by the service can be listed under <notsupported> element.

   The <supported> and <notsupported> elements can contain any values
   from the IANA SIP parameters registry option tags table followed by
   any number of optional extension elements from other namespaces.  As
   of today the IANA SIP parameters registry includes the following
   option tags: <rel100>, <early-session>, <eventlist>, <from-change>,
   <gruu>, <histinfo>, <join>, <norefersub>, <path>, <precondition>,
   <pref>, <privacy>, <replaces>, <resource-priority>, <sdp-anat>, <sec-
   agree>, <tdialog> and <timer>.

3.2.18.  <schemes> element

   The <schemes> element provides the set of URI schemes that are
   supported by a service.  Supported implies, for example, that the
   service would know how to handle a URI of that scheme in the Contact
   header field of a redirect response as defined in [RFC3840].

   The <schemes> element can contain two elements: <supported> and
   <notsupported>.  Schemes that are supported by the service can be
   listed under <supported> element and schemes that are not supported
   by the service can be listed under <notsupported> element.

   <supported> and <notsupported> elements can contain any number of <s>
   elements which can be used to describe individual schemes supported
   by the service.

3.2.18.1.  <s> element

   The <s> element is of string type and it is used to describe
   individual scheme supported by the service.  Values that can be used
   here are scheme names that are registered to IANA URI scheme
   registry.

3.2.19.  <actor> element

   The <actor> element indicates the type of entity that is available at
   this URI as defined in [RFC3840].

   The <actor> element can contain two elements: <supported> and
   <notsupported>.  Actor types that are supported by the service can be



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   listed under <supported> element and actor types that are not
   supported by the service can be listed under <notsupported> element.

   The <supported> and <notsupported> elements can contain <principal>,
   <attendant>, <msg-taker>, and <information> elements followed by any
   number of optional extension elements from other namespaces.

   The semantics of these elements are defined in [RFC3840] as:

   o  <principal>: The service provides communication with the principal
      that is associated with the service.  Often this will be a
      specific human being, but it can be an automata (for example, when
      calling a voice portal).

   o  <attendant>: The service provides communication with an automata
      or person that will act as an intermediary in contacting the
      principal associated with the service, or a substitute.

   o  <msg-taker>: The service provides communication with an automata
      or person that will take messages and deliver them to the
      principal.

   o  <information>: The service provides communication with an automata
      or person that will provide information about the principal.

   Any value that is registered with IANA for the SIP Media Feature Tag
   Registration Tree as a sip.class media feature tag can be used as a
   value of an extension element.  If the appropriate value is not
   registered it SHOULD be registered as defined in [RFC3840].

3.2.20.  <isfocus> element

   The <isfocus> element indicates that the service is a conference
   server, also known as a focus as defined in [RFC3840].

   The <isfocus> element is of boolean type and does not have any
   attributes.  The value 'true' indicates that service is a conference
   server and the value 'false' indicates that service does not support
   conferencing.

3.2.21.  <languages> element

   The <languages> element indicates the ability to display particular
   human languages as defined in [RFC4646].

   The <languages> element can contain two elements: <supported> and
   <notsupported>.  Languages that are supported by the service can be
   listed under <supported> element and languages that are not supported



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   by the service can be listed under <notsupported> element.

   <supported> and <notsupported> elements can contain any number of <l>
   elements which can be used to describe individual languages supported
   by the service.

3.2.21.1.  <l> element

   The <l> element is of string type and it is used to describe
   individual language supported by the service.  Values that can be
   used here are language names that are registered to IANA as per
   [RFC4646].

3.3.  Device capabilities

   Elements belonging to device capabilities are used to describe
   dynamic characteristics of a device.  These capabilities are enclosed
   within the <devcaps> element which SHOULD be located in the PIDF
   document as a child element of urn:ietf:params:xml:ns:pidf:data-model
   namespace <device> element [RFC4479].

   Namespace identifier for these elements is urn:

   ietf:params:xml:ns:pidf:caps

3.3.1.  <devcaps> element

   The root element of device capabilities is <devcaps>.  The root
   element has to be always present.  This element can contain following
   elements: <mobility> and <description> followed by any number of
   optional extension elements from other namespaces.

   A <devcaps> element can contain any number of optional extension
   attributes from other namespaces.

3.3.2.  <mobility> element

   The <mobility> element indicates whether the device is fixed (meaning
   that it is associated with a fixed point of contact with the
   network), or mobile (meaning that it is not associated with a fixed
   point of contact).  Note that cordless phones are fixed, not mobile,
   based on this definition as defined in [RFC3840].

   The <mobility> element can contain two elements: <supported> and
   <notsupported>.  Mobility modes that are supported by the device can
   be listed under <supported> element and all mobility modes that are
   not supported by the device can be listed under <notsupported>
   element.



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   The <supported> and <notsupported> elements can contain <fixed> and
   <mobile> elements followed by any number of optional extension
   elements from other namespaces.

   The semantics of these elements are defined in [RFC3840] as:

   o  <fixed>: The device is stationary.

   o  <mobile>: The device can move around with the user.

   Any value that is register to IANA to SIP Media Feature Tag
   Registration Tree as sip.mobility media feature tag can be used as a
   value of an extension element.  If the appropriate value is not
   registered it SHOULD be registered as defined in [RFC3840].

3.3.3.  <description> element

   The <description> element provides a textual description of the
   device as defined in [RFC3840].

   The <description> element is of string type and does not have any
   attributes.

   The <description> element SHOULD be labeled with the 'xml:lang'
   attribute to indicate its language and script.  The specification
   allows multiple occurrences of this elements so that the presentity
   can convey <description> elements in multiple scripts and languages.
   If no 'xml:lang' attribute is provided, the default value is
   "i-default" as defined in [RFC2277].


4.  Usage guidelines

   The User Agent Capabilities extension [RFC3840] recommends that a UA
   provides complete information in its contact predicate.  However, it
   may be that presentity is not willing to publish presence information
   which would be consistent with actual device or service capabilities
   (e.g. presentity may not want to indicate that he/she supports voice
   when the service actually is able to support it).  Authorization
   rules or policies in presence server may limit or modify the
   published presence information in a way that all published presence
   information may not end up to all possible watchers.  Also combining
   presence document from multiple sources may result in lose or
   mismatch of information.

   It is RECOMMENDED that Presence User Agents (PUAs) using this
   extension provide as complete presence information as they can.  If
   the PUA is publishing sensitive information using this extension, it



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   SHOULD obtain a permission from a user.  PUAs can indicate all the
   explicitly supported capabilities using the <supported> element and
   all the explicitly not supported capabilities using the
   <notsupported> element, where appropriate.

   It is not mandated that presence information should be consistent
   with actual service or device capabilities.  However, it is the
   presentity's best interest to avoid publishing false presence
   information and provide accurate information to help to minimize
   unsuccessful communication invitations.  Otherwise, watchers may
   conclude that communication cannot be established with the presentity
   but in reality it would be possible, or certain communication
   capabilities are available but in reality a communication
   establishment attempt would fail using those capabilities.  In any
   case, watchers should not expect the presence information represented
   by this extension to be fully aligned with the actual presentity's
   service or device capabilities.  As explained in section Section 1.2
   presence of this extension does not replace the use of SIP signaling
   for capability negotiation.

4.1.  Use of <supported> and <notsupported> elements

   PUAs should add information under <supported> and <notsupported>
   elements only when they believe it may affect the decision making in
   the watcher's end, i.e. information should be relevant and valuable
   for the watcher.  Listing all possible information under <supported>
   and <notsupported> is rarely needed.

   For example, if the PUA wants to advertise a message service that
   supports MESSAGE method it should add it under <supported> in
   <methods> element.  Even if the service does not support other
   methods it is unlikely that listing all the not supported methods
   under <notsupported> would provide any value to the watcher.

   In case of conflicting information, i.e. same child element appears
   under <supported> and <notsupported> elements with same value, the
   watcher can safely assume that the listed capability is supported
   regardless of the inclusion of the capability under the
   <notsupported> element.


5.  Examples

   <?xml version="1.0" encoding="UTF-8"?>
   <presence xmlns="urn:ietf:params:xml:ns:pidf"
         xmlns:caps="urn:ietf:params:xml:ns:pidf:caps"
         xmlns:mod="urn:ietf:params:xml:ns:pidf:data-model"
         entity="pres:someone@example.com">



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     <tuple id="joi9877866786ua9">
       <status>
         <basic>open</basic>
       </status>
       <caps:servcaps>
         <caps:audio>true</caps:audio>
         <caps:description xml:lang="en">
            Example service
         </caps:description>
         <caps:description xml:lang="hu">
            Pe'lda szolga'ltata's
         </caps:description>
         <caps:duplex>
           <caps:supported>
             <caps:full/>
           </caps:supported>
         </caps:duplex>
         <caps:message>true</caps:message>
         <caps:methods>
           <caps:supported>
             <caps:ACK/>
             <caps:BYE/>
             <caps:INVITE/>
           </caps:supported>
         </caps:methods>
         <caps:priority>
           <caps:supported>
             <caps:lowerthan maxvalue="10"/>
           </caps:supported>
         </caps:priority>
         <caps:schemes>
           <caps:supported>
             <caps:s>sip</caps:s>
           </caps:supported>
         </caps:schemes>
         <caps:video>false</caps:video>
       </caps:servcaps>
       <contact>sip:someone@example.com</contact>
     </tuple>
     <mod:device id="hgt67">
       <caps:devcaps>
         <caps:mobility>
           <caps:supported>
             <caps:mobile/>
           </caps:supported>
         </caps:mobility>
       </caps:devcaps>
       <mod:deviceID



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        >urn:uuid:d27459b7-8213-4395-aa77-ed859a3e5b3a</mod:deviceID>
     </mod:device>
   </presence>


6.  XML schema definitions

   This section gives the XML schema definitions for the extensions
   defined in this document.  Namespace identifier for this schema is
   urn:ietf:params:xml:ns:pidf:caps.

<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:tns="urn:ietf:params:xml:ns:pidf:caps"
  xmlns:xs="http://www.w3.org/2001/XMLSchema"
  targetNamespace="urn:ietf:params:xml:ns:pidf:caps"
  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"/>

<!-- ROOT -->
 <xs:element name="servcaps" type="tns:servcapstype"/>
 <xs:complexType name="servcapstype">
  <xs:sequence>
   <xs:element name="actor" type="tns:actortype"
    minOccurs="0"/>
   <xs:element name="application" type="tns:applicationtype"
    minOccurs="0"/>
   <xs:element name="audio" type="tns:audiotype" minOccurs="0"/>
   <xs:element name="automata" type="tns:automatatype"
    minOccurs="0"/>
   <xs:element name="class" type="tns:classtype"
    minOccurs="0"/>
   <xs:element name="control" type="tns:controltype"
    minOccurs="0"/>
   <xs:element name="data" type="tns:datatype"
    minOccurs="0"/>
   <xs:element name="description" type="tns:descriptiontype"
    minOccurs="0" maxOccurs="unbounded"/>
   <xs:element name="duplex" type="tns:duplextype"
    minOccurs="0"/>
   <xs:element name="event-packages" type="tns:event-packagestype"
    minOccurs="0"/>
   <xs:element name="extensions" type="tns:extensionstype"



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    minOccurs="0"/>
   <xs:element name="isfocus" type="tns:isfocustype"
    minOccurs="0"/>
   <xs:element name="message" type="tns:messagetype"
    minOccurs="0"/>
   <xs:element name="methods" type="tns:methodstype"
    minOccurs="0"/>
   <xs:element name="languages" type="tns:languagestype"
    minOccurs="0"/>
   <xs:element name="priority" type="tns:prioritytype"
    minOccurs="0"/>
   <xs:element name="schemes" type="tns:schemestype"
    minOccurs="0"/>
   <xs:element name="text" type="tns:texttype"
    minOccurs="0"/>
   <xs:element name="type" type="tns:typetype"
    minOccurs="0" maxOccurs="unbounded"/>
   <xs:element name="video" type="tns:videotype"
    minOccurs="0"/>
   <xs:any namespace="##other" processContents="lax"
    minOccurs="0" maxOccurs="unbounded"/>
  </xs:sequence>
 <xs:anyAttribute namespace="##any" processContents="lax"/>
 </xs:complexType>

 <xs:element name="devcaps" type="tns:devcaps"/>
 <xs:complexType name="devcaps">
  <xs:sequence>
   <xs:element name="description" type="tns:descriptiontype"
    minOccurs="0" maxOccurs="unbounded"/>
   <xs:element name="mobility" type="tns:mobilitytype"
    minOccurs="0"/>
   <xs:any namespace="##other" processContents="lax"
    minOccurs="0" maxOccurs="unbounded"/>
  </xs:sequence>
 <xs:anyAttribute namespace="##any" processContents="lax"/>
 </xs:complexType>

 <!-- AUDIO -->
 <xs:simpleType name="audiotype">
  <xs:restriction base="xs:boolean"/>
 </xs:simpleType>

 <!-- APPLICATION -->
 <xs:simpleType name="applicationtype">
  <xs:restriction base="xs:boolean"/>
 </xs:simpleType>




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 <!-- DATA -->
 <xs:simpleType name="datatype">
  <xs:restriction base="xs:boolean"/>
 </xs:simpleType>

 <!-- CONTROL -->
 <xs:simpleType name="controltype">
  <xs:restriction base="xs:boolean"/>
 </xs:simpleType>

 <!-- VIDEO -->
 <xs:simpleType name="videotype">
  <xs:restriction base="xs:boolean"/>
 </xs:simpleType>

 <!-- TEXT -->
 <xs:simpleType name="texttype">
  <xs:restriction base="xs:boolean"/>
 </xs:simpleType>

 <!-- MESSAGE -->
 <xs:simpleType name="messagetype">
  <xs:restriction base="xs:boolean"/>
 </xs:simpleType>

 <!-- TYPE -->
 <xs:simpleType name="typetype">
  <xs:restriction base="xs:string"/>
 </xs:simpleType>

 <!-- AUTOMATA -->
 <xs:simpleType name="automatatype">
  <xs:restriction base="xs:boolean"/>
 </xs:simpleType>

 <!-- CLASS -->
 <xs:complexType name="classtype">
  <xs:sequence>
   <xs:element name="supported" type="tns:classtypes"
    minOccurs="0"/>
   <xs:element name="notsupported" type="tns:classtypes"
    minOccurs="0"/>
  </xs:sequence>
 </xs:complexType>
 <xs:complexType name="classtypes">
  <xs:sequence>
   <xs:element name="business" type="xs:string"
    minOccurs="0"/>



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   <xs:element name="personal" type="xs:string"
    minOccurs="0"/>
   <xs:any namespace="##other" processContents="lax"
    minOccurs="0"
    maxOccurs="unbounded"/>
  </xs:sequence>
 </xs:complexType>

 <!-- DUPLEX -->
 <xs:complexType name="duplextype">
  <xs:sequence>
   <xs:element name="supported" type="tns:duplextypes"
    minOccurs="0"/>
   <xs:element name="notsupported" type="tns:duplextypes"
    minOccurs="0"/>
  </xs:sequence>
 </xs:complexType>
 <xs:complexType name="duplextypes">
  <xs:sequence>
   <xs:element name="full" type="xs:string"
    minOccurs="0"/>
   <xs:element name="half" type="xs:string"
    minOccurs="0"/>
   <xs:element name="receive-only" type="xs:string"
    minOccurs="0"/>
   <xs:element name="send-only" type="xs:string"
    minOccurs="0"/>
   <xs:any namespace="##other" processContents="lax"
    minOccurs="0" maxOccurs="unbounded"/>
  </xs:sequence>
 </xs:complexType>

 <!-- DESCRIPTION -->
 <xs:complexType name="descriptiontype">
  <xs:simpleContent>
   <xs:extension base="xs:string">
    <xs:attribute ref="xml:lang"/>
   </xs:extension>
  </xs:simpleContent>
 </xs:complexType>

 <!-- EVENT-PACKAGES -->
 <xs:complexType name="event-packagestype">
  <xs:sequence>
   <xs:element name="supported" type="tns:eventtypes"
    minOccurs="0"/>
   <xs:element name="notsupported" type="tns:eventtypes"
    minOccurs="0"/>



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  </xs:sequence>
 </xs:complexType>
 <xs:complexType name="eventtypes">
  <xs:sequence>
   <xs:element name="conference" type="xs:string"
    minOccurs="0"/>
   <xs:element name="dialog" type="xs:string"
    minOccurs="0"/>
   <xs:element name="kpml" type="xs:string"
    minOccurs="0"/>
   <xs:element name="message-summary" type="xs:string"
    minOccurs="0"/>
   <xs:element name="poc-settings" type="xs:string"
    minOccurs="0"/>
   <xs:element name="presence" type="xs:string"
    minOccurs="0"/>
   <xs:element name="reg" type="xs:string"
    minOccurs="0"/>
   <xs:element name="refer" type="xs:string"
    minOccurs="0"/>
   <xs:element name="Siemens-RTP-Stats"
    type="xs:string" minOccurs="0"/>
   <xs:element name="spirits-INDPs"
    type="xs:string" minOccurs="0"/>
   <xs:element name="spirits-user-prof"
    type="xs:string" minOccurs="0"/>
   <xs:element name="winfo" type="xs:string"
    minOccurs="0"/>
   <xs:any namespace="##other" processContents="lax"
    minOccurs="0" maxOccurs="unbounded"/>
  </xs:sequence>
 </xs:complexType>

 <!-- PRIORITY -->
 <xs:complexType name="prioritytype">
  <xs:sequence>
   <xs:element name="supported" type="tns:prioritytypes"
    minOccurs="0"/>
   <xs:element name="notsupported" type="tns:prioritytypes"
    minOccurs="0"/>
  </xs:sequence>
 </xs:complexType>
 <xs:complexType name="prioritytypes">
  <xs:sequence>
   <xs:element name="equals" type="tns:equalstype"
    minOccurs="0" maxOccurs="unbounded"/>
   <xs:element name="higherhan" type="tns:higherthantype"
    minOccurs="0" maxOccurs="unbounded"/>



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   <xs:element name="lowerthan" type="tns:lowerthantype"
    minOccurs="0" maxOccurs="unbounded"/>
   <xs:element name="range" type="tns:rangetype"
    minOccurs="0" maxOccurs="unbounded"/>
   <xs:any namespace="##other" processContents="lax"
    minOccurs="0" maxOccurs="unbounded"/>
  </xs:sequence>
 </xs:complexType>
 <xs:complexType name="lowerthantype">
  <xs:attribute name="maxvalue" type="xs:integer"
   use="required"/>
 </xs:complexType>
 <xs:complexType name="higherthantype">
  <xs:attribute name="minvalue" type="xs:integer"
   use="required"/>
 </xs:complexType>
 <xs:complexType name="equalstype">
  <xs:attribute name="value" type="xs:integer"
   use="required"/>
 </xs:complexType>
 <xs:complexType name="rangetype">
  <xs:attribute name="minvalue" type="xs:integer"
   use="required"/>
  <xs:attribute name="maxvalue" type="xs:integer"
   use="required"/>
 </xs:complexType>

 <!-- METHODS -->
 <xs:complexType name="methodstype">
  <xs:sequence>
   <xs:element name="supported" type="tns:methodtypes"
    minOccurs="0"/>
   <xs:element name="notsupported" type="tns:methodtypes"
    minOccurs="0"/>
  </xs:sequence>
 </xs:complexType>
 <xs:complexType name="methodtypes">
  <xs:sequence>
   <xs:element name="ACK" type="xs:string" minOccurs="0"/>
   <xs:element name="BYE" type="xs:string" minOccurs="0"/>
   <xs:element name="CANCEL" type="xs:string" minOccurs="0"/>
   <xs:element name="INFO" type="xs:string" minOccurs="0"/>
   <xs:element name="INVITE" type="xs:string" minOccurs="0"/>
   <xs:element name="MESSAGE" type="xs:string" minOccurs="0"/>
   <xs:element name="NOTIFY" type="xs:string" minOccurs="0"/>
   <xs:element name="OPTIONS" type="xs:string" minOccurs="0"/>
   <xs:element name="PRACK" type="xs:string" minOccurs="0"/>
   <xs:element name="PUBLISH" type="xs:string" minOccurs="0"/>



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   <xs:element name="REFER" type="xs:string" minOccurs="0"/>
   <xs:element name="REGISTER" type="xs:string" minOccurs="0"/>
   <xs:element name="SUBSCRIBE" type="xs:string" minOccurs="0"/>
   <xs:element name="UPDATE" type="xs:string" minOccurs="0"/>
   <xs:any namespace="##other" processContents="lax" minOccurs="0"
    maxOccurs="unbounded"/>
  </xs:sequence>
 </xs:complexType>

 <!-- EXTENSIONS -->
 <xs:complexType name="extensionstype">
  <xs:sequence>
   <xs:element name="supported" type="tns:extensiontypes"
    minOccurs="0"/>
   <xs:element name="notsupported" type="tns:extensiontypes"
    minOccurs="0"/>
  </xs:sequence>
 </xs:complexType>
 <xs:complexType name="extensiontypes">
  <xs:sequence>
   <xs:element name="rel100" type="xs:string" minOccurs="0"/>
   <xs:element name="early-session" type="xs:string" minOccurs="0"/>
   <xs:element name="eventlist" type="xs:string" minOccurs="0"/>
   <xs:element name="from-change" type="xs:string" minOccurs="0"/>
   <xs:element name="gruu" type="xs:string" minOccurs="0"/>
   <xs:element name="hist-info" type="xs:string" minOccurs="0"/>
   <xs:element name="join" type="xs:string" minOccurs="0"/>
   <xs:element name="norefersub" type="xs:string" minOccurs="0"/>
   <xs:element name="path" type="xs:string" minOccurs="0"/>
   <xs:element name="precondition" type="xs:string" minOccurs="0"/>
   <xs:element name="pref" type="xs:string" minOccurs="0"/>
   <xs:element name="privacy" type="xs:string" minOccurs="0"/>
   <xs:element name="replaces" type="xs:string" minOccurs="0"/>
   <xs:element name="resource-priority" type="xs:string" minOccurs="0"/>
   <xs:element name="sdp-anat" type="xs:string" minOccurs="0"/>
   <xs:element name="sec-agree" type="xs:string" minOccurs="0"/>
   <xs:element name="tdialog" type="xs:string" minOccurs="0"/>
   <xs:element name="timer" type="xs:string" minOccurs="0"/>
   <xs:any namespace="##other" processContents="lax"
    minOccurs="0" maxOccurs="unbounded"/>
  </xs:sequence>
 </xs:complexType>

 <!-- SCHEMES -->
 <xs:complexType name="schemestype">
  <xs:sequence>
   <xs:element name="supported" minOccurs="0">
    <xs:complexType>



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     <xs:sequence>
      <xs:element name="s" type="xs:string" maxOccurs="unbounded"/>
     </xs:sequence>
    </xs:complexType>
   </xs:element>
   <xs:element name="notsupported" minOccurs="0">
    <xs:complexType>
     <xs:sequence>
      <xs:element name="s" type="xs:string" maxOccurs="unbounded"/>
     </xs:sequence>
    </xs:complexType>
   </xs:element>
  </xs:sequence>
 </xs:complexType>

 <!-- ACTOR -->
 <xs:complexType name="actortype">
  <xs:sequence>
   <xs:element name="supported" type="tns:actortypes"
    minOccurs="0"/>
   <xs:element name="notsupported" type="tns:actortypes"
    minOccurs="0"/>
  </xs:sequence>
 </xs:complexType>
 <xs:complexType name="actortypes">
  <xs:sequence>
   <xs:element name="attendant" type="xs:string" minOccurs="0"/>
   <xs:element name="information" type="xs:string" minOccurs="0"/>
   <xs:element name="msg-taker" type="xs:string" minOccurs="0"/>
   <xs:element name="principal" type="xs:string" minOccurs="0"/>
   <xs:any namespace="##other" processContents="lax" minOccurs="0"
    maxOccurs="unbounded"/>
  </xs:sequence>
 </xs:complexType>

 <!-- ISFOCUS -->
 <xs:simpleType name="isfocustype">
  <xs:restriction base="xs:boolean"/>
 </xs:simpleType>

 <!-- LANGUAGES -->
 <xs:complexType name="languagestype">
  <xs:sequence>
   <xs:element name="supported" minOccurs="0">
    <xs:complexType>
     <xs:sequence>
      <xs:element name="l" type="xs:string" maxOccurs="unbounded"/>
     </xs:sequence>



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    </xs:complexType>
   </xs:element>
   <xs:element name="notsupported" minOccurs="0">
    <xs:complexType>
     <xs:sequence>
      <xs:element name="l" type="xs:string" maxOccurs="unbounded"/>
     </xs:sequence>
    </xs:complexType>
   </xs:element>
  </xs:sequence>
 </xs:complexType>

 <!-- MOBILITY -->
 <xs:complexType name="mobilitytype">
  <xs:sequence>
   <xs:element name="supported" type="tns:mobilitytypes"
    minOccurs="0"/>
   <xs:element name="notsupported" type="tns:mobilitytypes"
    minOccurs="0"/>
  </xs:sequence>
 </xs:complexType>
 <xs:complexType name="mobilitytypes">
  <xs:sequence>
   <xs:element name="fixed" type="xs:string"
    minOccurs="0"/>
   <xs:element name="mobile" type="xs:string"
    minOccurs="0"/>
   <xs:any namespace="##other" processContents="lax" minOccurs="0"
    maxOccurs="unbounded"/>
  </xs:sequence>
 </xs:complexType>
</xs:schema>

                                 Figure 1


7.  IANA Considerations

   This memo calls for IANA to register one new XML namespace URNs as
   defined in [RFC3688].

7.1.   URN sub-namespace registration for
      'urn:ietf:params:xml:ns:pidf:caps'

   URI:
   urn:ietf:params:xml:ns:pidf:caps

   Description:



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   This is the XML namespace for XML elements defined by [[[RFCXXXX]]]
   to describe service and device capabilities in application/pidf+xml
   content type.

   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>Namespace for PIDF user agent capability
               extension</title>
   </head>
   <body>
       <h1>Namespace for PIDF service capability extension</h1>
       <h2>urn:ietf:params:xml:ns:pidf:caps</h2>
       <p>See <a href="[[[URL of published RFC]]]">RFCXXXX</a>.</p>
    </body>
    </html>
   END


8.  Security Considerations

   All security considerations specified in [RFC3859] and [RFC3863]
   apply to this document.  Compared to PIDF [RFC3863] this presence
   document format may reveal additional information about user's
   service and device capabilities.  Thus, the PUA SHOULD always obtain
   permission from the user when publishing sensitive information using
   this extension.


9.  Acknowledgments

   Authors of this document would like to thank following people for
   their contributions and valuable comments: Paul Kyzivat, Jonathan
   Rosenberg, Markus Isomaki, Eva Leppanen, Miguel Garcia, Jari
   Urpalainen, and Hisham Khartabil.





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10.  References

10.1.  Normative references

   [RFC3859]  Peterson, J., "Common Profile for Presence (CPP)",
              RFC 3859, August 2004.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC3863]  Sugano, H., Fujimoto, S., Klyne, G., Bateman, A., Carr,
              W., and J. Peterson, "Presence Information Data Format
              (PIDF)", RFC 3863, August 2004.

   [RFC3840]  Schulzrinne, H., Rosenberg, J., and P. Kyzivat,
              "Indicating User Agent Capabilities in the Session
              Initiation Protocol (SIP)", RFC 3840, August 2004.

   [RFC2913]  Klyne, G., "MIME Content Types in Media Feature
              Expressions", RFC 2913, September 2000.

   [RFC4646]  Phillips, A. and M. Davis, "Tags for Identifying
              Languages", RFC 4646, September 2006.

   [RFC3688]  Mealling, M., "The IETF XML Registry", RFC 3688, BCP 81,
              January 2004.

   [RFC4479]  Rosenberg, J., "A Data Model for Presence", RFC 4479,
              July 2006.

   [RFC2045]  Freed, N. and N. Borenstein, "Multipurpose Internet Mail
              Extensions (MIME) part one: Format of Internet Message
              Bodies", RFC 2045, November 1996.

   [RFC2277]  Alvestrand, H., "IETF Policy on Character Sets and
              Languages", RFC 2277, January 1998.

10.2.  Informative references

   [RFC4569]  Camarillo, G., "Internet Assigned Numbers Authority (IANA)
              Registration of the Message Media Feature Tag", RFC 4569,
              July 2006.

   [RFC3860]  Peterson, J., "Common Profile for Instant Messaging
              (CPIM)", RFC 3860, August 2004.

   [RFC4566]  Handley, M., Jacobson, V., and C. Perkins, "SDP: Session
              Description Protocol", RFC 4566, July 2006.



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   [RFC2778]  Day, M., Rosenberg, J., and H. Sugano, "A Model for
              Presence and Instant Messaging", RFC 2778, February 2000.

   [RFC2648]  Moats, R., "A URN namespace for IETF documents", RFC 2648,
              Aug. 1999.


Authors' Addresses

   Mikko Lonnfors
   Nokia
   P.O. Box 321
   Helsinki
   Finland

   Phone: +358 71 8008000
   Email: mikko.lonnfors@nokia.com


   Krisztian Kiss
   Nokia
   313 Fairchild Dr
   Mountain View, CA 94043
   US

   Phone: +1 650 391 5969
   Email: krisztian.kiss@nokia.com
























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