One document matched: draft-khartabil-simple-presence-filter-00.txt
SIP Hisham Khartabil
Internet Draft Mikko Lonnfors
Expires: July, 2003 Jose Costa-Requena
Eva Leppanen
Nokia
January, 2002
Event Notification Filtering for Presence
draft-khartabil-simple-presence-filter-00.txt
STATUS OF THIS MEMO
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
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This Internet Draft will expire on xxxx, 2003.
Copyright Notice
Copyright (C) The Internet Society (2002). All Rights Reserved.
Abstract
The Presence event package for the SIP events framework describes
the usage of the Session Initiation Protocol (SIP) for subscriptions
and notifications of user presence. The document details how
watchers can subscribe for notifications of all authorised and
available presence information about the presentity. The document
does not describe a mechanism of how filtering of presence
information can be achieved.
This document defines a presence filter package for the Event
Notification Filtering Architecture. The package provides the
mechanism whereby a watcher can specify the presence event filtering
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rules, using XML, for the presence agent (PA) and how that PA is to
behave when receiving such filter.
Table of Contents
1.0 Terminology.......................................................3
2.0 Introduction......................................................3
2.1 Motivation For Using XML..........................................4
3.0 Presence Package Specific Filters.................................4
3.1 Package ID........................................................4
3.3 Transport mechanism...............................................5
3.4 Structure of XML-Encoded Presence Filter Criteria.................5
3.4.1 The <ev-filter-set> Root Element................................5
3.4.2 The <ev-filter> Element.........................................5
3.4.3 The <what> Element..............................................6
5.0 Client and server operation.......................................6
5.1 Client Operation..................................................6
5.1.1 SUBSCRIBE Bodies................................................6
5.1.2 Subscriber Generating SUBSCRIBE requests........................7
5.1.2.1 To-Header vs. Filter URI......................................7
5.1.2.2 Changing The Filter Criteria Within A Dialog..................8
5.1.2.3 Subscriber Interpreting SIP responses.........................8
5.1.3 Subscriber processing of NOTIFY requests........................9
5.2 Server Operation..................................................9
5.2.1 NOTIFY Bodies...................................................9
5.2.2 Notifier processing of SUBSCRIBE Requests.......................9
5.2.2 Notifier Generation of NOTIFY requests.........................10
5.2.2.1 Generating NOTIFY Contents...................................10
6.0 IANA Considerations..............................................11
7.0 Examples.........................................................11
7.1 Subscriber requests messaging related information................12
7.2 Subscriber fetches information about "open" communication means..13
8.0 Presence Package Specific Filters XML Schema.....................15
9.0 Security Requirements............................................16
10.0 Acknowledgements................................................17
11.0 References......................................................17
AuthorsÆ Addresses...................................................18
Full Copyright Statement.............................................19
Acknowledgement......................................................19
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1.0 Terminology
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 [12].
The document uses the terms as defined in [1], [2] and [3].
2.0 Introduction
User presence is defined as the ability to express willingness and
ability of a user to communicate with other users on the network
[2].
SIP event notification is described in [4]. It defines a general
framework for sending subscriptions and receiving notifications in
SIP based systems. It introduces the concept of event packages,
which are concrete applications of the general event framework to a
specific usage of events. An event package for user presence is
defined in [2].
Filtering is a mechanism for controlling the content of event
notifications [5]. Additionally the subscriber may specify the rules
for when a notification should be sent to it.
The filtering mechanism is expected to be particularly valuable to
users of mobile wireless access devices. The characteristics of the
devices typically include high latency, low bandwidth, low data
processing capabilities, small display, and limited battery power.
Such devices can benefit from the ability to filter the amount of
information generated at the source of the event notification.
It is stated in [2] that the notifier (Presence Agent) may send a
NOTIFY at any time, but typically it is sent when the state of the
presentity changes. It also states that the notifications would
contain the complete and current presence state of the presentity
authorized for a certain subscriber to see. The format of such
presence information is named Presence Information Data Format
(PIDF), as defined in [3].
This document presents a mechanism for the filtering of the PIDF
based presence information. The document specifically describes how
the subscriber is able to both limit the content and indicate more
specifically the prefered content of the notifications using XML and
Xpath [15] technologies. It also describes how the presence agent
(PA) functions when generating notifications by taking into account
filters, authorisation rules and default functionality of the
presence service.
The presence specific filtering solution presented here is
compatible with the Presence Event Package [2].
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Requirements for the Presence filter criteria can be found from two
drafts:
The 3GPP Presence requirements document [14] sets the following
requirement: "It must be possible for a watcher to select certain
elements from the presence information that he wants (or does not
want) to receive in notifications for."
The filter requirements draft [5] presents the following case: "A
watcher wishes to get to know presentity's availability and
willingness for messaging (e.g. IM and MMS)."
Events Notification RFC [4] and the SIMPLE working group both
identify filtering work as potential work.
2.1 Motivation For Using XML
When trying to select the schema and protocol for defining the
filter criteria, it can be found that there are several alternatives
available. The best practice is to modularise the problem and work
on smaller modules (the protocol and the filter information schema).
The selection of the schema for defining the filter criteria
requires a readable syntax with enough flexibility to define the
semantics.
Among the multiple possibilities (i.e. XML, Perl, TCL, etc), XML
provides a generic framework where a schema for the filter logic
including a namespace allowing the definition of the filter
criteria. Thus, an XML schema provides an extensible mechanism where
the logic required for the filtering functionality can be built. XML
provides extensibility based on "namespaces" associated with a
globally unique URI.
The XML also enables the use of Xpath [15] for referencing items in
an XML document (which is in the case of Presence in the format of
the PIDF).
In addition, by using XML the need for reliance on the transport
protocol in order to interpret the filter criteria can be
eliminated.
3.0 Presence Package Specific Filters
This section describes the technologies and information needed to
provide a filter specification relevant to presence filtering.
3.1 Package ID
The package ID is æpresenceÆ or ôpresence.listö. This ID is carried
in the event-header of the SUBSCRIBE as well as within the XML
document carrying filter criteria.
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3.3 Transport mechanism
Transportation of the filter criteria to the server is achieved by
inserting the filter XML document in the body of a SIP SUBSCRIBE
request. Alternatively, the document can be uploaded to the server
using a transport specific for data manipulation.
3.4 Structure of XML-Encoded Presence Filter Criteria
Presence Filter Criteria is an XML document [7] that MUST be well-
formed and SHOULD be valid. Presence Filter Criteria XML documents
MUST have the XML declaration and it SHOULD contain an encoding
declaration in the XML declaration e.g. "<?XML version='1.0'
encoding='UTF-8'?>". This specification makes use of XML
namespaces for identifying the XML schema of the Presence Filter
Criteria documents and document fragments.
The namespace identifier for elements defined by this specification
is a URN [8], using the namespace identifier 'ietf' defined by [9]
and extended by [10]. This urn is:
urn:ietf:params:xml:ns:simple-pres-filter+xml.
This namespace declaration indicates the namespace on which the
filter criteria are based on.
3.4.1 The <ev-filter-set> Root Element
The root element of the filter criteria is <ev-filter-set>. The <ev-
filter-set> MAY have a 'pkgdef' attribute that defines the
'Presence' or 'presence.list' as package for the filter criteria.
The <ev-filter-set> root element MUST contain the namespace
mentioned above. This element MUST contain one or more <ev-filter>
elements.
3.4.2 The <ev-filter> Element
The <ev-filter> element is used to specify the content of an
individual filter.
<ev-filter> MUST have an 'id' attribute. The value of the 'id'
attribute MUST be unique within the <ev-filter-set> root element.
<ev-filter> MUST have an 'uri' attribute. The value of the 'uri'
attribute is the URI of the PRESENTITY or URI of the set of
presentities from whom presence information is requested.
The URI of the PRESENTITY is useful in cases where the ælistÆ
template package [6] is used with æpresenceÆ package and different
filter criteria are defined for one or more members of the
presence.list.
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The <ev-filter> element MUST contain a <what> element.
OPEN ISSUE: The solution for defining conditions when notifications
are triggered is defined in future versions of this document.
3.4.3 The <what> Element
The <what> element is used to specify the content to be delivered to
the WATCHER. It does not specify the exact content but rules that
are used to construct that information.
The <what> element MUST contain the 'report' attribute. The value of
the 'report' is either 'default' or 'list-selected'. The 'default'
value means that also all the values of the selected PIDF XML
attributes and elements are delivered. The 'list-selected' means
that only the selected items are delivered. Note that all the
namespace definitions related to the delivered content are always
delivered.
3.4.3.1 Defining the delivered content
It must be possible in the filter criteria to be able to select
presence attributes and/or tuples of the default presence
information format [3]. It must also be possible to reference
presence information of any extensions as the PIDF allows extensions
to be defined as own namespaces.
A general way to reference any items (PIDF XML elements and
attributes) of the presence information is to be specified. The
referencing mechanism should support hierarchy of the items since
there may be several nested PIDF XML elements and attributes in the
presence information.
The preferred presence information is indicated using the
capabilities of XPath [15]. The XPath clause is stated in the value
of the <What> element. The items addressed with the XPath are
indicated with the expanded name which means that the URI of the
presence information namespace is included in addition to the
reference to the presence information item.
5.0 Client and server operation
5.1 Client Operation
5.1.1 SUBSCRIBE Bodies
SIP entities compliant with this specification MUST support content-
type æapplication/simple-pres-filter+xmlÆ.
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5.1.2 Subscriber Generating SUBSCRIBE requests
This section presents additional functionalities required from the
subscriber when filters are used in SUBSCRIBE requests bodies.
Normal operations as defined in [2] are then followed.
As defined in [2], a SUBSCRIBE for presence MAY contain a body. This
body, as defined in this document, would serve the purpose of
filtering. Honouring of these filters is at the policy discretion of
the PA.
No content in the body of a SUBSCRIBE indicates to the PA that no
filter is being requested; so that the PA is instructed to send all
NOTIFY requests including presence states that its own policy
allows.
If present, the body MUST be of MIME-Type æapplication/simple-pres-
filter+xmlÆ.
5.1.2.1 To-Header vs. Filter URI
The Event package "presence" in Event-header of the SUBSCRIBE
request specifies that the filter rules apply to the presence
information of the URI indicated in filter, or the URI present in
the To-header if no URI is indicated in the filter.
If the template package ôlistö is used with ôpresenceö in the
SUBSCRIBE, and no presentity URI is indicated by the filter, the
filter rules apply to all the URIs that result from a lookup, by the
Presence Agent, on the URI present in the To-header if no presentity
URI is indicated in the filter.
If the template package ôlistö is used with ôpresenceö in the
SUBSCRIBE, and the URI indicated by the filter in a presence list
URI, the filter rules apply to all the URIs that result from a
lookup, by the Presence Agent, on the URI in the filter.
If the template package ôlistö is used with ôpresenceö in the
SUBSCRIBE, and the presentity URI indicated by the filter in for one
presentity whoÆs URI is one of the URIs that result from a lookup,
by the PA, on the URI in the To-header, the filter rules apply to
that particular presentity. All other presence documents sent to the
rest of the presentities are not affected by the filter. For
example, if the To-header in a SUBSCRIBE has the URI
sip:mybuddies@mydomain.com, and the URI in the filter is
sip:bob@otherdomain.com, the filter only applied to
bob@otherdomain.com.
If the template package ôlistö is used with ôpresenceö in the
SUBSCRIBE, and the presentity URI indicated by the filter in for one
presentity whoÆs URI is NOT one of the URIs that result from a
lookup, by the PA, on the URI in the To-header, the filter rules do
not apply to that any particular presentity and are ignored. All
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presence documents sent to the presentities are not affected by the
filter.
Multiple filter criteria MAY be included in one SUBSCRIBE. This is
achieved by including multiple <ev-filter> elements.
A SUBSCRIBE request destined to a presence list MAY include multiple
filter criteria specific to individual presentities in that presence
list. This is achieved by including multiple <ev-filter> elements
with differing URIs for presentities in each of those elements. This
presentity specific filter overrides any presence list specific
filter, if any. Presence list specific filter may or may not include
a URI.
5.1.2.2 Changing The Filter Criteria Within A Dialog
The client MAY reset or change the filter criteria by re-issuing a
new SUBSCRIBE request within the existing dialog. The SUBSCRIBE
provides the "replace" semantics. This means that all filters are
replaced. A SUBSCRIBE within the exiting dialogs that does not
contain a filter is assumed to be removing all filter criteria.
As mentioend earlier, If the template package ôlistö is used with
ôpresenceö in the SUBSCRIBE, the rules apply to all the URIs that
result from a lookup, by the Presence Agent, on the URI in the
filter criteria. A watcher may override a filter for an individual
presentity, that is part of the presence list subscribed to earlier,
by issuing a new SUBSCRIBE within the existing dialog. The new
filter includes 2 <ev-filter> elemets, one for that presentity who
filter criteria needs changing, and the other for the presence list
(to avoid the replacement of the original filter criteria).
5.1.2.3 Subscriber Interpreting SIP responses
The SUBSCRIBE request will be confirmed with a final response. 200-
class responses indicate that the subscription has been accepted,
and that a NOTIFY will be sent immediately. A 200 response indicates
that the subscription has been accepted, the user is authorized to
subscribe to presence and that the filter is accepted. A 202
response merely indicates that the subscription has been understood,
the content type has been accepted, and that authorization may or
may not have been granted. A 202 response also indicates that the
filter has not been accepted yet. The acceptation of the filter MAY
arrive in a subsequent NOTIFY.
Non-200 class final responses indicate that no subscription or
dialog has been created, and no subsequent NOTIFY message will be
sent. All non-200 class responses have the same meanings and
handling as described in RFC 3261 [11] and RFC 3265[4].
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Specifically, a 415 response indicates that the MIME-type
æapplication/simple-pres-filter+xmlÆ is not understood by the
server. A 488 response indicates that the content (filter) is
understood but some aspects of it were either not understood or not
accepted.
5.1.3 Subscriber processing of NOTIFY requests
If a 2xx response was returned for the SUBSCRIBE, the NOTIFY that
follows MAY contain a body that describes the presence state of the
resource after the filter has been applied.
If the NOTIFY indicates that a subscription has been terminated [4],
the subscription is assumed to be terminated. Behaviour in such
events is also described in [4].
If the subscription is indicated as active, NOTIFY requests are
handled as described in [2] and [4].
5.2 Server Operation
5.2.1 NOTIFY Bodies
SIP entities compliant with this specification MUST support content-
type æapplication/simple-pres-filter+xmlÆ.
5.2.2 Notifier processing of SUBSCRIBE Requests
This section present addition functionalities required from the
notifier when filters are used in SUBSCRIBE requests bodies. Normal
operations as defined in [2] are then followed.
If 2 <ev-filter> elements address the same presentity, 488 error
response is returned.
The presence agent will examine the content-type header and will
return a 415 response if it does not understand content-type
æapplication/simple-pres-filter+xmlÆ.
If the presence agent accepts the content-type, it then starts
parsing the body. It returns a 488 response if the body is
understood but some aspects of the contents (filter) were not
understood and accepted. A warning header in the response may give a
better indication why the filters are not supported.
A 200-class responses indicate that the subscription has been
accepted, and that a NOTIFY will be sent immediately. A 200 response
indicates that the subscription has been accepted, the user is
authorized to subscribe to presence and that the filter is accepted.
A 202 response merely indicates that the subscription has been
understood, and that authorization may or may not have been granted.
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A 202 response also indicates that the filter has not been accepted
yet. The acceptation of the filter MAY arrive in a subsequent
NOTIFY.
5.2.2 Notifier Generation of NOTIFY requests
Upon receiving the SUBSCRIBE with the filtering rules, the Presence
Agent SHOULD retain the filter as long as the subscription persists.
The filter SHOULD persist as long as the subscription is active. The
filter MAY be incorporated within an existing subscription (an
active dialog) by sending a re-SUBSCRIBE that includes the filter in
the body.
If the response sent to the SUBSCRIBE was a 202, and the 202 was
chosen because the filter could not be accepted in time, the NOTIFY
MAY be used to terminate the subscription if the filter was not
found acceptable.
As described in [2], the NOTIFY message MAY contain a body that
describes the presence state of the resource. This body is in a
format listed in the Accept header of the SUBSCRIBE, or the presence
specific default æapplication/cpim-pidf+xmlÆ if the Accept header is
omitted.
5.2.2.1 Generating NOTIFY Contents
The input to the filter is a PIDF document [3] derived according to
the normal functionality defined in [2].
The content is filtered according to the XPath expression. The XPath
expression indicates the delivered PIDF XML elements and/or
attributes. Prefixes of the namespaces of the items of the PIDF XML
document to be filtered must be expanded before applying the filter
to the items.
The 'report' attribute indicates whether the values of the selected
items are delivered or not. If the value of the æreportÆ is "only-
selected" the XPath expression directly states the delivered
content. In case the value of the 'report' is "default" all the
values and attributes of the selected elements are delivered. In
addition to the selected contents also the namespaces of all the
selected presence information items are conveyed.
5.2.3 Handling of abnormal cases
In case of an unvalid filter definition û the filter XML document is
not aligned with the filter XML schema, the presence agent rejects
the SUBSCRIBE request with a 488. If the subscription was accepted
with a 202 response and the filter is being evaluated after that, a
NOTIFY with a subscription-state of terminated is sent. An event-
reason-value of ôbadfilterö MAY be included.
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The above paragraph introduces an extension to the event-reason-
value of subexp-params. The value, as shown above, is ôbadfilterö.
In case of an errorneous XPath clause in the filter definition the
presence agent either ignores the filter definition or terminates
the subscription.
In case of indication of empty content by the XPath clause the
presence agent functions according to the normal procedure for the
content filtering described in this document.
6.0 IANA Considerations
A new content type "application/simple-pres-filter+xml" is defined
to represent an XML MIME for the filter criteria of Presence.
A new event-reason-value ôbadfilterö is defined to represent a the
event where a filter is not well formed and not accpeted.
This specification follows the guidelines of RFC3023 [12].
OPEN ISSUE: IANA registration template must be added later.
(Note/Reminder: We must add IANA registration template for this)
7.0 Examples
This chapter describes two use cases where the presence information
filtering solution is utilised. In the first use case the watcher is
intrested in getting messaging specific information of a certain
presentity. In the second use case the watcher is intrested in
getting information about the communication means and contact
addresses the presentity is currently available for communication
on.
Below is the Presentity's presence information in PIDF. It includes
two tuples: one for the instant messaging and another for the voice
related information.
<?xml version="1.0" encoding="UTF-8"?>
<presence xmlns="urn:ietf:params:xml:ns:cpim-pidf"
xmlns:cpref="urn:example-com:pidf-prefscaps"
entity="sip:presentity@domain.com">
<tuple id="432sd">
<status>
<basic>closed</basic>
</status>
<cpref:prefscaps>
<cpref:Media>message</cpref:Media>
<cpref:Description>IM</cpref:Description>
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</cpref:prefscaps>
<contact>im:presentity@domain.com</contact>
</tuple>
<tuple id="thr76jk">
<status>
<basic>open</basic>
</status>
<cpref:prefscaps>
<cpref:Description>voice</cpref:Description>
</cpref:prefscaps>
<contact>tel:2224055555@domain.com</contact>
</tuple>
</presence>
7.1 Subscriber requests messaging related information
The subscriber initiates a subscription to the presentity's
messaging (MMS, IM and SMS) related presence information. The
subscription includes the content limiting filter.
The filtered content is indicated with the Xpath expression. This
Xpath expression selects all the upper, lower and paraller level
PIDF XML elements that match the criteria. That criteria are:
Description elements whoÆs value begins with "MMS", "SMS" or "IM".
The 'default' value of the report attribute states that also the
PIDF XML attributes related to the selected PIDF XML elements and
values of the selected PIDF XML elements are requested to be
included.
In this case, the notification includes the contents of the tuple
that has the value "IM" in its callerprefs element's description
sub-element.
SUBSCRIBE request from the subscriber including filtering:
SUBSCRIBE sip:presentity@domain.com
Via: SIP/2.0/TCP 10.0.0.1:5060;branch=xjfdsjfk
To: <sip:presentity@domain.com>
From: <sip:watcher@domain.com>;tag:12341111
Call-ID: 121212@10.0.0.1
Cseq: 1 SUBSCRIBE
Expires: 3600
Event: Presence
Contact: <sip:watcher@domain.com>
Content-Type: application/simple-pres-filter+xml
Content-Length: à
<?xml version="1.0" encoding="UTF-8"?>
<ev-filter-set xmlns="urn:ietf:params:xml:ns:simple-pres-filter"
>
<ev-filter id = "mess" uri="sip:presentity@domain.com">
<what report="default">
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//*[starts-with(urn:example-com:pidf-
prefscaps/Description,"IM") or starts-with(urn:example-com:pidf-
prefscaps/Description,"SMS") or starts-with(urn:example-com:pidf-
prefscaps/Description,"MMS")]/descendant-or-self::*/ancestor-or-
self::*
</what>
</ev-filter>
</ev-filter-set>
Notification to the subscriber:
NOTIFY sip:presentity@domain.com SIP/2.0
Via: SIP/2.0/TCP presence.domain.com:5060;branch=xjfder
To: <sip:watcher@domain.com>;tag:12341111
From: <sip:presentity@domain.com>;tag:232321
Call-ID: 121212@10.0.0.1
Cseq: 1 NOTIFY
Event: Presence
Subscription-State: active; expires=3599
Content-Type: application/cpim-pidf+xml
Content-Length: à
<?xml version="1.0" encoding="UTF-8"?>
<presence xmlns="urn:ietf:params:xml:ns:cpim-pidf"
xmlns:cpref="urn:example-com:pidf-prefscaps"
entity="sip:presentity@domain.com">
<tuple id="432sd">
<status>
<basic>closed</basic>
</status>
<cpref:calleeprefs>
<cpref:Media>message</cpref:Media>
<cpref:Description>IM</cpref:Description>
</cpref:calleeprefs>
<contact>im:presentity@domain.com</contact>
</tuple>
</presence>
7.2 Subscriber fetches information about "open" communication means
The subscriber makes a subscription to the presentity's available
communication means. The subscription includes the content limiting
filter.
The filtered content is indicated with the Xpath expression. This
Xpath expression selects all the upper, lower and paraller level
PIDF XML elements that match the criteria. That criteria are: the
<basic> element's value is "Open". There is also need to indicate
that only the tuples which have contact address information are
selected. The 'default' value of the report attribute states that
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also the PIDF XML attributes related to the selected PIDF XML
elements and values of the selected PIDF XML elements are requested
to be included.
In this case the notification returns the contents of the tuple that
has value is "open" û the voice related information in its status
element's basic sub-element.
SUBSCRIBE request from the subscriber including filtering:
SUBSCRIBE sip:presentity@domain.com SIP/2.0
Via: SIP/2.0/TCP 10.0.0.1:5060;branch=xjfdsjfk
To: <sip:presentity@domain.com>
From: <sip:watcher@domain.com>;tag:12341111
Call-ID: 121212@10.0.0.1
Cseq: 1 SUBSCRIBE
Expires: 3600
Event: Presence
Contact: <sip:watcher@domain.com>
Content-Type: application/simple-pres-filter+xml
Content-Length: à
<?xml version="1.0" encoding="UTF-8"?>
<ev-filter-set xmlns="urn:ietf:params:xml:ns:simple-pres-filter">
<ev-filter id = "open_mean" uri="sip:presentity@domain.com">
<what report="default">
//*[urn:ietf:params:xml:ns:cpim-pidf/basic="Open" and
urn:ietf:params:xml:ns:cpim-pidf/contact]/descendant-or-
self::*/ancestor-or-self::*
</what>
</ev-filter>
</ev-filter-set>
Notification to the subscriber:
NOTIFY sip:presentity@domain.com SIP/2.0
Via: SIP/2.0/TCP presence.domain.com:5060;branch=xjfder
To: <sip:watcher@domain.com>;tag:12341111
From: <sip:presentity@domain.com>;tag:232321
Call-ID: 121212@10.0.0.1
Cseq: 1 NOTIFY
Event: Presence
Subscription-State: active; expires=3599
Content-Type: application/cpim-pidf+xml
Content-Length: à
<?xml version="1.0" encoding="UTF-8"?>
<presence xmlns="urn:ietf:params:xml:ns:cpim-pidf"
xmlns:cpref="urn:example-com:pidf-prefscaps"
entity="sip:presentity@domain.com">
<tuple id="thr76jk">
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Internet Draft Congestion Safety and C-I July 2002
<status>
<basic>open</basic>
</status>
<cpref:prefscaps>
<cpref:Description>voice</cpref:Description>
</cpref:prefscaps>
<contact>tel:2224055555@domain.com</contact>
</tuple>
</presence>
8.0 Presence Package Specific Filters XML Schema
*******************
XML Schema Implementation (Normative)
<?xml version="1.0" encoding="UTF-8"?>
<!-- *********************************************************** -->
<xsd:schema targetNamespace="urn:ietf:params:xml:ns:simple-pres-
filter"
xmlns:xsd=http://www.w3.org/2001/XMLSchema/>
<xsd:import namespace="http://www.w3.org/XML/1998/namespace"
schemaLocation="http://www.w3.org/2001/xml.xsd"> <!ùlang -->
<xsd:annotation>
<xsd:documentation xml:lang="en">
XML Schema Definition for SIP Event Filtering for Presence.
Copyright 2002. Nokia. All rights reserved.
</xsd:documentation>
</xsd:annotation>
<!-- *********************************************************** -->
<xsd:element name="ev-filter-set" type="EventFilterSetType"/>
<!--
The "pkgdef" attribute is useful to identify the event package
explicitly within the filter document (e.g. when the filtering
is decoupled from the transport
-->
<xsd:complexType name="EventFilterSetType">
<xsd:sequence>
<xsd:element name="ev-filter" type="EventFilterType"
minOccurs="1" maxOccurs="unbounded"/>
</xsd:sequence>
<xsd:attribute name="pkgdef" type="xsd:string" use="optional"/>
</xsd:complexType>
<!--
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Internet Draft Congestion Safety and C-I July 2002
An event filter corresponds to the SIP URI indicated by its "uri"
attribute. The URI defines of the presentity. -->
<xsd:complexType name="EventFilterType">
<xsd:sequence>
<xsd:element name="what" type="WhatType" use="required"/>
</xsd:sequence>
<xsd:attribute name="id" type="xsd:string" use="required"/>
<!-- <xsd:attribute name="uri" type="xsd:string" use="required"/> -
->
<xsd:attribute name="uri" type="xsd:anyURI" use="optional/>
</xsd:complexType>
<xsd:complexType name="WhatType">
<xsd:simpleContent>
<xsd:extension base="xsd:string">
<xsd:attribute name="report" type="ReportType" use="required"/>
</xsd:extension base>
</simpleContent>
</xsd:complexType>
<xsd:simpleType name="ReportType">
<xsd:restriction base="xsd:string">
<xsd:enumeration value="default"/>
<xsd:enumeration value="only-selected"/>
</xsd:restriction>
</xsd:simpleType>
<!-- *********************************************************** -->
</xsd:schema>
<!-- *
9.0 Security Requirements
The presence of filters in the body in a SIP message has a
significant effect on the ways in which the request is handled at a
server. As a result, it is especially important that messages
containing this extension be authenticated and authorized.
Processing of requests and looking up filter criteria requires set
operations and searches, which can require some amount of
computation. This enables a DOS attack whereby a user can send
Khartabil, et. al. [Page 16]
Internet Draft Congestion Safety and C-I July 2002
requests with substantial numbers messages with large contents, in
the hopes of overloading the server. To counter this, the server
SHOULD only allow filters with no more than about 20 rules.
Requests can reveal sensitive information about a UAÆs capabilities.
If this information is sensitive, it SHOULD be encrypted using SIP
S/MIME capabilities.
All presence related security measures discussed in [2] MUST be
followed.
10.0 Acknowledgements
The authors would like to thank Tim Moran and Sreenivas Addagatla
for their valuable input.
11.0 References
[1] M. Day, J. Rosenberg, H. Sugano, "A Model for Presence and
Instant Messaging", RFC 2778, Internet Engineering Task Force,
February 2000.
[2] Rosenberg, J., et al, "SIP Extensions for Presence", draft-ietf-
simple-presence-07.txt. Internet Draft, May 2002, Work in progress.
[3] H. Sugano, S. Fujimoto, et al, "CPIM presence information data
format," draft-ietf-impp-cpim-pidf-05.txt. Internet Draft, May 2002.
Work in progress.
[4] Roach, A., "SIP-Specific Event Notification", RFC 3265, Internet
Engineering Task Force, June 2002.
[5] Moran, T., " Requirements for Presence specific Event
Notification Filters ", draft-moran-simple-pres-filter-reqs-00.txt.
Internet Draft, October 2002, Work in progress.
[6] Roach, A., " SIP Event Template Package for Collections", draft-
roach-sip-list-template-00. Internet Draft, October 2002. Work in
progress.
[7] W. W. W. C. (W3C), "Extensible markup language (xml) 1.0." The
XML 1.0 spec can be found at http://www.w3.org/TR/1998/REC-xml-
19980210.
[8] R. Moats, "URN syntax," RFC 2141, Internet Engineering Task
Force, May 1997.
[9] R. Moats, "A URN namespace for IETF documents," RFC 2648,
Internet Engineering Task Force, Aug. 1999.
Khartabil, et. al. [Page 17]
Internet Draft Congestion Safety and C-I July 2002
[10] M. Mealling, "The IETF XML registry", draft-mealling-iana-
xmlns-registry-04.txt. Internet Draft. November 2001. Work in
progress.
[11] J. Rosenberg, et al. ôSIP: Session Initiation Protocolö. RFC
3261, Internet Engineering Task Force, June 2002.
[12] M. Murata, S. S. Laurent, and D. Kohn, "XML media types," RFC
3023, Internet Engineering Task Force, Jan. 2001.
[13] S. Bradner, "Key words for use in RFCs to indicate requirement
levels," RFC 2119, Internet Engineering Task Force, Mar. 1997.
[14] K.Kiss, ôRequirements for Presence Service based on 3GPP
specifications and wireless environment characheristicsö draft-kiss-
simple-presence-wireless-reqs-01.txt. Internet Draft, October 2002.
Work in progress.
[15] W. W. W. C. (W3C), "XML Path Language (Xpath)". W3C
Recommendation. <link - http://www.w3.org/TR/xpath >
AuthorsÆ Addresses
Hisham Khartabil
Nokia
P.O. Box 321
FIN-00045
NOKIA GROUP
FINLAND
Email: hisham.khartabil@nokia.com
Tel: + 358 7180 76161
Jose Costa-Requena
Nokia
P.O. Box 321
FIN-00045
NOKIA GROUP
FINLAND
Email: jose.costa-requena@nokia.com
Tel: +358 71800 8000
Mikko Lonnfors
Nokia Research Center
P.O. Box 407
FIN-00045 NOKIA GROUP
Khartabil, et. al. [Page 18]
Internet Draft Congestion Safety and C-I July 2002
Finland
Tel: +358 50 4836402
Email: mikko.lonnfors@nokia.com
Eva Leppanen
Nokia
P.O Box 785
FIN-33101 Tampere
FINLAND
Tel: +358 7180 77066
Email: eva-maria.leppanen@nokia.com
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Khartabil, et. al. [Page 19]
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