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Internet Engineering Task Force
Internet Draft                                            H. Schulzrinne
                                                             Columbia U.
                                                              P. Kyzivat
                                                              V. Gurbani
                                                            J. Rosenberg
February 18, 2003
Expires: August 2003

RPIDS -- Rich Presence Information Data Format for Presence Based on the Session
                       Initiation Protocol (SIP)


   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as Internet-

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress".

   The list of current Internet-Drafts can be accessed at

   To view the list Internet-Draft Shadow Directories, see


   The Rich Presence Information Data Format for SIP (RPIDS) adds
   elements to the Presence Information Data Format (PIDF) that provide
   additional information about the presentity and its contacts. This
   information can be translated into call routing behavior and/or be
   delivered to watchers. The information is designed so that much of it
   can be derived automatically, e.g., from calendar files or user

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1 Introduction

   The PIDF definition [1] describes a basic presence infornation data
   format for exchanging presence information in CPIM-compliant systems.
   It consists of a <presence> root element, zero or more <tuple>
   elements carrying presence information, zero or more <note> elements
   and zero or more extension elements from other name spaces.  Each
   tuple defines a basic status of either "open" or "closed".

   This document provides additional status information for presentities
   and defines a Rich Presence Information Data Format for Presence
   Based on the Session Initiation Protocol (SIP) (RPIDS) to convey this

   This extension has two main goals:

        1.   Provide rich presence indication that is at least as
             powerful as common commercial presence systems. Such
             feature-parity simplifies transition to CPIM-compliant
             systems, both in terms of user acceptance and protocol

        2.   Maintain compatibility with PIDF, so that PIDF-only
             watchers and gateways can continue to function properly.

   The document here is complementary to the device capability
   descriptions derived from caller preferences [8]. Both can be used as
   extensions within the same PIDF document.

   We make no assumptions how the information in the RPIDS is generated.
   Experience has shown that users are not always diligent about
   updating their presence status. Thus, we want to make it as easy as
   possible to derive RPIDS information from other information sources,
   such as calendars, the status of communication devices such as
   telephones, typing activity and physical presence detectors as
   commonly found in energy-management systems.

   The information in a presence document can be generated by a single
   entity or can be composed from information published by multiple

   Many of the elements correspond to data commonly found in personal
   calendars. Thus, we attempted to align some of the extensions with
   the usage found in calendar formats such as iCal [9] and xCal [10],
   as noted below.

   Note that PIDF documents and this extension can be used in two
   different contexts, namely by the presentity to publish its presence

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   status and by the presence server to notify some set of watchers. The
   presence server MAY compose, translate or filter the published
   presence state before delivering customized presence information to
   the watcher. For example, it may merge presence information from
   multiple PUAs, remove whole elements, translate values in elements or
   remove information from elements. Mechanisms that filter calls and
   other communications to the presentity can subscribe to this presence
   information just like a regular watcher and in turn generate
   automated rules, such as scripts [11], that govern the actual
   communications behavior of the presentity.

   The flow diagram below illustrates this process.

      --> publish
            --> PA (filter)
                    --> notification 1 to A, B, C
                    --> notification 2 to D, E
                    --> notification 3 to F
                    --> notification 4 to script gen.

2 RPIDS Features

   Below, we summarize and motivate the major additional features that
   RPIDS adds to PIDF.

   The PIDF definition does not clearly describe what a <tuple>
   represents. We add an <class> element (Section 6.3) that labels each
   tupel as being a presentity, a group of presentities or a device.

   While the PIDF definition describes which means of communications are
   available for a presentity, it does not describe the activity that
   the presentity is currently engaged in. The <category> (Section 6.6)
   element adds this information.

   To help the watcher gauge the appropriateness of different types of
   communications, we indicate the type of place the user is currently
   in, via the <placetype> element (Section 6.4).

   PIDF defines a <timestamp> element indicating the date and time of
   the status change of a tuple. RPIDS adds a validity period for status
   values, <from> and <until>, as a hint how long the current status is
   likely to be valid (Section 6.7 and Section 6.8).

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   The <activity> (Section 6.9) and <idlesince> (Section 6.10) provide
   information on when the device has last been used.

   Presence information can provide hints as to how interruptible the
   presentity is, thus aiding in finding a time and manner of
   communications that is mutually convenient for both watcher and
   presentity. The "priority" callee capability described in [12] and,
   by reference, included in [8] offers this capability.  This appears
   to be more expressive than the simple "do-not-disturb" indication
   found in some IM and presence systems.

   An important sub-case is that a presentity is interruptible only
   under unusual circumstances, after mediation by some, typically
   human, authority such as a secretary or supervisor. We allow the
   presentity to convey that certain contact addresses actually belong
   to a different person, presumably one that can either interrupt the
   presentity or otherwise assist. The <relationship> (Section 6.11)
   element allows to indicate that a particular tuple refers to a
   different principal or presentity.

   PIDF only defines tuples for one presentity. In many cases, it is
   useful to allow presentities to refer to groups of other
   presentities.  For example, a presentity all@example.com might
   consist of

   marketing@example.com ,
   engineering@example.com , finance@example.com

   engineering@example.com might in turn have presentities

   alice@example.com ,
   bob@example.org (an intern), carol@example.com ,

   We add multiple layer to PIDF by defining an extension (Section 6.13)
   that can in turn contain multiple PIDF presence elements, thus
   allowing recursion.

   We establish the convention that a tuple that has no contact address
   indicates face-to-face communications. PIDF already notes that "there
   might be tuples not related to any communications means".

   We generally assume that the presence element describes a single
   human being or a group of humans. However, this is not required. A
   presentity can also be a "bot" or "avatar", for example.

   Note that this document does not defined a new content type. Rather,
   it inherits the content type from [1], namely application/cpim-

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   Other useful information about tuples is defined in [8]. In
   particular, that document allows to describe the media types
   supported by a contact address, whether it supports recording and the
   minimum priority of calls admitted.

3 Terminology and Conventions

   This memo makes use of the vocabulary defined in the IMPP Model
   document [2]. Terms such as CLOSED, INSTANT MESSAGE, OPEN, PRESENCE
   used in the same meaning as defined therein. The key words MUST,
   in this document are to be interpreted as described in BCP XX, RFC
   2119 [3].

4 The Meaning of "open" and "closed"

   PIDF describes the basic status values of "open" or "closed" only as
   "have meanings of general availability for other communications
   means". We define "closed" in our context as meaning that
   communication to the contact address will in all likelihood not
   succeed, is undesired or will not reach the intended party. (For
   example, a presentity may include a hotel phone number as a contact.
   After check-out, the phone number will still ring, but reach the
   chambermaid or the next guest. Thus, it would be declared "closed".)
   For "pres" contacts, "closed" means that no presence status
   information is available.

        The interpretation of "closed" was chosen since there is no
        other status value to indicate that a communications
        address is not reachable. Omitting the <contact> element
        does not work since it would confuse watchers that have not
        previously seen an "open" status for the same contact

5 Groups of Presentities

   In many practical applications, a watcher wants to subscribe to
   groups of presentities rather than individuals. For example, the
   group membership may change over time and it may thus be difficult to
   subscribe to all members. If the group is large, the effort of
   subscription and their renewals may add significant burden to the

   There are several different approaches to group subscriptions:

        Group only: The watcher subscribes to a group and only cares

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             about the status of the group as a whole. There is no
             protocol difference to subscribing to an individual and
             thus no need for extensions.

        Subscription only: The watcher subscribes to a group, but
             receives individual notifications. This does not require an
             extensions to PIDF. However, it is useful to indicate in
             the presence document which presentity caused the
             notification to be sent, as the watcher otherwise has no
             idea why he received a particular notification. We add a
             <parent> element to describe this relationship.

        Subscription with redirection: The watcher subscribes to a
             group.  The presence document identifies the group members
             and allows the watcher to subscribe to each member
             individually. In PIDF, this is expressed by a "pres" URI in
             the <contact> element. Each such presentity can in turn be
             a group, recursively. TBD: How does the watcher find out if
             group membership has changed? We don't want to list all
             members in each PIDF notification. This basically becomes

        Subscription with full status: A single notification contains
             tuples from all presentities that have changed status since
             the last notification. We allow "recursive" presence
             definitions, where a <presence> element contains other
             <presence> elements, encapsulated as <members> (Section

6 RPIDS Elements

6.1 Introduction

   Below, we describe the RPIDS elements in detail.  <activity>,
   <category>, <class>, <from>, <idlesince> <label>, <placetype>,
   <privacy>, <relationship>, <until> extend <status>.  <members>
   extends the <presence> element.

   In general, it is highly unlikely that a presentity will publish or
   announce all of these elements at the same time. Rather, these
   elements were chosen to give the presentity maximum flexibility in
   deriving this information from existing sources, such as calendaring
   tools, device activity sensors or location trackers, as well as to
   manually configure this information.

   The namespace URI for elements defined by this specification is a URN
   [4], using the namespace identifier 'ietf' defined by [5] and
   extended by [6]:

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6.2 Label

   The <label> attribute is used by the presentity to label tuples. The
   value is chosen arbitrarily and MUST NOT be modified by a composing
   server or PA. There is no requirement that all tuples within a
   presence document differ in their label or have a label at all.
   Typically, the label remains the same across subscriptions and across

        The <label> makes it easier for policies to operate on
        presence documents. The 'id' <tuple> attribute is not
        guaranteed to remain constant across subscriptions. The
        PIDF specification does not prevent a PA from modifying the
        'id' attribute.  An element, rather than an attribute, was
        chosen since it appears less likely to cause
        interoperability problems with plain PIDF parsers.

6.3 Contact-Type

   The <contact-type> element describes the type of the tuple.  A tuple
   can represent a communication facility ("device"), a single
   presentity ("individual") or a group of presentities ("group").
   Additional classes can be registered with IANA.

        URI schema are insufficient to distinguish the different
        types of tuples. For example, a SIP URI can designate a
        single device, a presentity, or a group of presentities.

6.4 Type of Place

   The <placetype> element describes the type of place the presentity is
   currently at. This offers the watcher an indication what kind of
   communication is likely to be appropriate. We define an initial set
   of values below:

        home: The presentity is in a private or residential setting, not
             necessarily the personal residence of the presentity, e.g.,
             including hotel or a friend's home.

        office: The presentity is in a business setting, such as an

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        public: The presentity is in a public area such as a shopping
             mall, street, park, public building, train station, airport
             or in public conveyance such as a bus, train, plane or

   This list can be augmented by free-text values or additional IANA-
   registered values (Section 10).

6.5 Privacy

        public: Others may be able to see or hear the communications.

        private: Inappropriate individuals are not likely to see or hear
             the communications.

        quiet: The presentity is in a place such as a library,
             restaurant, place-of-worship, or theater that discourages
             noise, conversation and other distractions.

   This indication is not limited to voice communications. For example,
   a presentity might label her privacy as "quiet" when giving a talk,
   since it would be inappropriate if an instant message popped up on
   the laptop screen that is being projected for the audience.

6.6 Category Indications

   The <category> indication describes what the presentity is currently
   doing. This can be quite helpful to the watcher in judging how
   appropriate a communication attempt is and which means of
   communications is most likely to succeed and not annoy the
   presentity.  The activity indications correspond roughly to the
   category field in calendar entries, such as Section of RFC
   2445 [9].

        Use of an enumerated, but extensible, set of activity
        categories simplifies automated generation and processing
        of presence information. The categories can be readily
        selected from a drop-down list by the user or translated
        from the corresponding category field in calendars.
        Recipients of this information can render at least a subset
        as icons, automatically translate them into different
        languages or convert them to sound "jingles" and speech, or
        use them to generate call processing rules.

   A category indication consists of one or more values drawn from the
   list below, any other token string or IANA-registered values (Section
   10). Communities of interest such as a profession or an organization

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   may define additional activity labels for their internal use.

        On-the-phone: The presentity is talking on the telephone. This
             category is included since it can often be derived

        Away: The presentity is physically away from the device
             location. This category was included since it can often be
             derived automatically from security systems, energy
             management systems or entry badge systems.

        Appointment: The presentity has a calendar appointment.

        Holiday: This is a scheduled national or local holiday. This
             information can typically be derived automatically from

        Meal: The presentity is scheduled for a meal. This category can
             often be generated automatically from a calendar.

        Meeting: This category can often be generated automatically from
             a calendar.

        Steering: The presentity is controlling a vehicle, ship or

        In-transit: The presentity is riding in a vehicle, such as a
             car, but not steering.

        Travel: The presentity is on a business or personal trip, but
             not necessarily in-transit. This category can often be
             generated automatically from a calendar.

        Vacation: This category can often be generated automatically
             from a calendar.

        Busy: User is busy, without further details. This category would
             typically be indicated manually.

        Permant-absence: Presentity will not return for the foreseeable
             future, e.g., because it is no longer working for the

6.7 From

   The <from> element indicates how long the current status has been
   valid, expressed as an absolute time.

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6.8 Until

   The <until> element indicates how long the current basic status (open
   or closed) is likely to be valid, expressed as an absolute time.

   This indication allows the watcher to make better decisions. For
   example, if a presentity indicates that it is likely to be
   unreachable for an extended period of time, the watcher may decide to
   request assistance from somebody else, rather than waiting for the
   presentity to return.

   Often, the duration of the status information is not known precisely.
   Thus, it is helpful to indicate the precision, here expressed in
   seconds. For example, an absence of "a few hours" can easily be
   expressed as a time some hours into the future, with a precision of
   7200 seconds.

        An absolute time was chosen to simplify integration with
        calendaring applications. This combination appears to be
        sematically cleaner than enumerating various measurement
        units such as "months", "weeks", "days" or "hours".

   Both the <from> and <until> information might be derived from
   calendar information, reflecting the start and end time of an
   activity. (Examples include the Date Time Start and Date Time End
   properties of RFC 2445. For simplicity, RPIDS only supports single
   events, without repetition.)

   Any statements such as anticipated validity are not historical facts
   and are forward-looking statements that involve risks and
   uncertainties; actual results may differ from the forward-looking

6.9 Activity

   The <activity> element describes whether the owner of the device has
   recently been actively using the device or not. It can take the
   values "active" and "inactive". For example, for a PC, the value
   "inactive" may be inferred from the lack of keyboard and mouse
   activity. For a telephone, an ongoing call translates into "active".

        The idle indication has been available in many "finger"
        implementations for several decades.

        The <activity> indication provides a qualitative indication

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        that reveals less information to watchers than the
        <idlesince> element

6.10 Idlesince

   The <idlesince> records the time and date the communication device
   was last used. This provides an indication as to how likely a user is
   to answer the device. Depending on the device, this element can be
   used together with <activity>, either "active" or "inactive". For
   example, a keyboard activity detector may still declare a PC that has
   not seen keyboard activity in two minutes as "active". For session-
   based devices such as telephones and video conferencing systems,
   <idlesince> would only be used with an activity value of "inactive".

6.11 Relationship

   The <relationship> element designates the type of relationship an
   alternate contact has with the presentity. This element is provided
   only if the tuple refers to somebody other than the presentity.
   Relationship values include "family", "associate" (e.g., for a
   colleague), "assistant", "supervisor". Other free-text values and
   additional IANA-registered values (Section 10) can be used as well.

   The <contact> element can contain either a communication URI such as
   "im", "sip"/"sips", "h323", "tel" or "mailto", or a presence URI,
   such as "pres" or "sip". The method value in the <prescaps> element
   [8] allows the watcher to determine whether a "sip" URI is meant to
   indicate a presence or communications URI.

6.12 Timed Status

   The <timed-status> describes status information that is either no
   longer valid or covers some future timeperiod.

        Timed status cannot be expressed with <tuples> elements
        where the period between <status> since PIDF parsers would
        not be able to distinguish current from future or past
        information. It is 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.

6.13 Members

   The <members> element contains zero or more <presence> elements, each

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   describing a member of the group.  It is not necessary to provide the
   <basic> status for each member.

        Since the extension namespace for <presence> is restricted
        to ##other, we cannot include the PIDF <presence> directly.

7 Examples

7.1 Single presentity

   <?xml version="1.0" encoding="UTF-8"?>
      <presence xmlns="urn:ietf:params:xml:ns:cpim-pidf"

        <note>I'm in a boring meeting</note>

        <tuple id="7c8dqui">
          <note>My secretary</note>

        <tuple id="18x765">
          <contact priority="0.8">sip:someone@example.com</contact>


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        <tuple id="35bs9r">
          <contact priority="0.8">im:someone@mobilecarrier.net</contact>

        <tuple id="8eg92n">
          <contact priority="1.0">mailto:someone@example.com</contact>

7.2 Multiple Presentities

   <?xml version="1.0" encoding="UTF-8"?>
      <presence xmlns="urn:ietf:params:xml:ns:cpim-pidf"

      <tuple id="478">

        <presence ... entity="pres:alice@example.com">
          <tuple id="1">

        <presence ... entity="pres:bob@example.com">
          <tuple id="2">

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        <presence ... entity="pres:widget-engineering@example.com">
          <tuple id="3">



8 XML Schema Definition

   <?xml version="1.0" encoding="UTF-8"?>
      <xs:schema targetNamespace="urn:ietf:params:xml:ns:sip-rpids"

     <!-- This import brings in the XML language attribute xml:lang-->
         <xs:import namespace="http://www.w3.org/XML/1998/namespace"

     <xs:element name="contact-type" type="tns:contact-type"/>
     <xs:element name="placetype" type="xs:token"/>
     <xs:element name="privacy" type="tns:privacy"/>
     <xs:element name="category" type="xs:token"/>
     <xs:element name="relationship" type="xs:token"/>
     <xs:element name="from" type="tns:fromuntil">
     <xs:element name="until" type="tns:fromuntil">
     <xs:element name="idlesince" type="xs:dateTime">

     <xs:element name="timed-status" type="tns:timed-status">

     <xs:simpleType name="contact-type">
       <xs:restriction base="xs:string">
          <xs:enumeration value="individual"/>
          <xs:enumeration value="device"/>

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          <xs:enumeration value="group"/>

     <xs:simpleType name="privacy">
       <xs:restriction base="xs:string">
          <xs:enumeration value="private"/>
          <xs:enumeration value="public"/>
          <xs:enumeration value="quiet"/>

     <xs:complexType name="fromuntil">
         <xs:extension base="xs:dateTime">

     <xs:complexType name="timed-status">
         <xs:element name="basic" type="pidf:basic" minOccurs="0"/>
         <xs:element name="from" type="tns:fromuntil">
         <xs:element name="until" type="tns:fromuntil">
         <xs:element name="note" type="pidf:note">
         <xs:any namespace="##other" processContents="lax" minOccurs="0"

     <xs:complexType name="members">
         <xs:any namespace="pidf" processContents="lax" minOccurs="0"

9 Security Considerations

   The security considerations in [1] apply, as well as [7]. Compared to
   PIDF, this presence document format reveals additional information
   that can be highly sensitive. Beyond traditional security measures to
   protect confidentiality and integrity, systems should offer a means
   to selectively reveal information to particular watchers and to
   inspect the information that is being published, particularly if it
   is generated automatically from other sources, such as calendars or

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10 IANA Considerations

   This document calls for IANA to:

        o register a new XML namespace URN per [6];

        o establish registry for categories (Section 6.6), place types
          (Section 6.4), and relationships (Section 6.11).

   Note that this document does not need a new content type. It inherits
   the content type from [1], namely application/cpim-pidf+xml

10.1 URN Sub-Namespace Registration for

        URI: urn:ietf:params:xml:ns:sip-rpids

        Description: This is the XML namespace for XML elements defined
             by RFCXXXX to describe a rich presence information
             extension for the CPIM-PIDF presence document format in the


        content type.

        Registrant Contact:  IETF, SIMPLE working group,
             Henning Schulzrinne, <hgs@cs.columbia.edu>


                <?xml version="1.0"?>
                <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML Basic 1.0//EN"
                <html xmlns="http://www.w3.org/1999/xhtml
                     <meta http-equiv="content-type"
                     <title>RPIDS -- Rich Presence Information Data Format
               for Presence Based on the Session
               Initiation Protocol (SIP)</title>
                    <h1>Namespace for SIMPLE rich presence extension</h1>
                    <p>See <a href="[[[URL of published RFC]]]">RFCXXXX</a>.</p>

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10.2 Place Type, Device Type, Categories, Relationships

   This document creates new IANA registries for categories, device
   types, place types and relationships. All are XML tokens. Registered
   tokens must be documented at the time of registration, as most
   descriptions are expected to be brief.

   The SIMPLE working group, or, if no longer available, the SIP working
   group should be consulted prior to registration.

11 Acknowledgements

   The document reflects the discussion on the SIMPLE mailing list, with
   contributions from many individuals. Hisham Khartabil, Jon Peterson
   and Brian Rosen provided detailed comments and suggestions.

12 Normative References

   [1] H. Sugano, S. Fujimoto, et al., "Common presence and instant
   messaging (cpim)presence information data format," internet draft,
   Internet Engineering Task Force, Jan. 2003.  Work in progress.

   [2] M. Day, J. Rosenberg, and H. Sugano, "A model for presence and
   instant messaging," RFC 2778, Internet Engineering Task Force, Feb.

   [3] S. Bradner, "Key words for use in rfcs to indicate requirement
   levels," RFC 2119, Internet Engineering Task Force, Mar. 1997.

   [4] R. Moats, "URN syntax," RFC 2141, Internet Engineering Task
   Force, May 1997.

   [5] R. Moats, "A URN namespace for IETF documents," RFC 2648,
   Internet Engineering Task Force, Aug. 1999.

   [6] M. Mealling, "The IETF XML registry," internet draft, Internet
   Engineering Task Force, July 2002.  Work in progress.

   [7] J. Rosenberg, "A presence event package for the session
   initiation protocol (SIP)," internet draft, Internet Engineering Task
   Force, Dec. 2002.  Work in progress.

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13 Informative References

   [8] M. Lonnfors and K. Kiss, "SIMPLE PIDF presence capabilities
   extension," internet draft, Internet Engineering Task Force, Oct.
   2002.  Work in progress.

   [9] F. Dawson and D. Stenerson, "Internet calendaring and scheduling
   core object specification (icalendar)," RFC 2445, Internet
   Engineering Task Force, Nov. 1998.

   [10] F. D. Jr., S. M. Reddy, D. Royer, and E. Plamondon, "icalendar
   DTD document (xcal)," internet draft, Internet Engineering Task
   Force, July 2002.  Work in progress.

   [11] J. Lennox and H. Schulzrinne, "CPL: a language for user control
   of Internet telephony services," internet draft, Internet Engineering
   Task Force, Nov. 2001.  Work in progress.

   [12] H. Schulzrinne and J. Rosenberg, "Session initiation protocol
   (SIP) caller preferences and callee capabilities," internet draft,
   Internet Engineering Task Force, Nov. 2002.  Work in progress.

14 Authors' Addresses

   Henning Schulzrinne
   Dept. of Computer Science
   Columbia University
   1214 Amsterdam Avenue
   New York, NY 10027
   Email: schulzrinne@cs.columbia.edu

   Paul Kyzivat
   Cisco Systems
   Mail Stop LWL3/12/2
   900 Chelmsford St.
   Lowell, MA 01851
   Email: pkzivat@cisco.com

   Vijay Gurbani
   2000 Naperville Rd., Room 6G-440
   Naperville, IL 60566-7033
   Email: vkg@lucent.com

   Jonathan Rosenberg

H. Schulzrinne et. al.                                       [Page 18]

Internet Draft                   RPIDS                 February 18, 2003

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H. Schulzrinne et. al.                                       [Page 19]

                           Table of Contents

   1          Introduction ........................................    2
   2          RPIDS Features ......................................    3
   3          Terminology and Conventions .........................    5
   4          The Meaning of "open" and "closed" ..................    5
   5          Groups of Presentities ..............................    5
   6          RPIDS Elements ......................................    6
   6.1        Introduction ........................................    6
   6.2        Label ...............................................    7
   6.3        Contact-Type ........................................    7
   6.4        Type of Place .......................................    7
   6.5        Privacy .............................................    8
   6.6        Category Indications ................................    8
   6.7        From ................................................    9
   6.8        Until ...............................................   10
   6.9        Activity ............................................   10
   6.10       Idlesince ...........................................   11
   6.11       Relationship ........................................   11
   6.12       Timed Status ........................................   11
   6.13       Members .............................................   11
   7          Examples ............................................   12
   7.1        Single presentity ...................................   12
   7.2        Multiple Presentities ...............................   13
   8          XML Schema Definition ...............................   14
   9          Security Considerations .............................   15
   10         IANA Considerations .................................   16
   10.1       URN Sub-Namespace Registration for ..................   16
   10.2       Place Type, Device Type, Categories, Relationships
   ................................................................   17
   11         Acknowledgements ....................................   17
   12         Normative References ................................   17
   13         Informative References ..............................   18
   14         Authors' Addresses ..................................   18

H. Schulzrinne et. al.                                        [Page 1]

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