SIMPLE WG T. Moran
Internet-Draft
Expires: November 9, 2003 S. Addagatla
E. Leppanen
Nokia
May 11, 2003
Requirements for Presence Specific Event Notification Filtering
draft-ietf-simple-pres-filter-reqs-00
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Copyright Notice
Copyright (C) The Internet Society (2003). All Rights Reserved.
Abstract
This document defines a set of structured requirements whereby a
presence information subscriber may select specific information to be
received in the presence infomation notification sent by the
notifier. The purpose is to limit the content and frequency of
notifications so that only essential information on a need basis is
delivered by the server.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Requirements for Specification of Filters . . . . . . . . . 4
3.1 Common Syntax . . . . . . . . . . . . . . . . . . . . . . . 4
3.2 Package Identification . . . . . . . . . . . . . . . . . . . 4
3.3 Target URI . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.4 Notification Triggering . . . . . . . . . . . . . . . . . . 4
3.5 Notification Content Limiting . . . . . . . . . . . . . . . 5
4. Requirements for Uploading Rules (Operational Rules) . . . . 5
4.1 SUBSCRIBE Method . . . . . . . . . . . . . . . . . . . . . . 5
4.1.1 Retention of Filter Settings . . . . . . . . . . . . . . . . 5
4.1.2 Changing Filter Settings . . . . . . . . . . . . . . . . . . 6
4.2 Server does not Support Filters . . . . . . . . . . . . . . 6
4.3 Server does not Support Filter Settings . . . . . . . . . . 6
4.4 Server can no Longer Support Filter Settings . . . . . . . . 6
5. Security Considerations . . . . . . . . . . . . . . . . . . 6
6. Example Applications for Notification Filtering . . . . . . 6
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7
References . . . . . . . . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 7
Intellectual Property and Copyright Statements . . . . . . . 9
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1. Introduction
SIP event notification is described in [6]. It defines a general
framework for subscriptions and notifications for SIP event packages.
Concrete applications of the general event framework to a specific
group of events are described in [5] (user presence) and [7] (watcher
information).
The presence information refers to a set of presence attributes
describing the availability and willingness of the user (presentity)
for communication. The user makes his presence information available
for other users (watchers).
As the inherent usage of event packages grows, the client needs some
mechanisms for controlling the event notifications at the source.
Evidence of this need is found in [4].
The Internet Draft describing the Presence event package [5] mentions
the possibility for a filtering. Accordingly, the SUBSCRIBE request
may contain a body for filtering the presence information
subscription. However, the definition of the filtering has been left
out of the scope of the Internet Draft. As an example, the body of
the SUBSCRIBE request may include a restriction on the set of data
returned in NOTIFY requests.
These mechanisms are expected to be particularly valuable to users of
wireless devices. The characteristics of these devices typically
include 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.
However, it is expected that the control mechanisms for event
notifications add value for all users irrespectively of their device
or network access characteristics.
Section 3 and Section 4 of this draft propose a set of requirements
whereby a client may specify which notifications it is interested in.
That is, a means to specify filtering rules to be executed by the
server. Section 6 provides a few example applications of notification
filtering.
2. Conventions
In this document, the key words 'MUST', 'MUST NOT', 'REQUIRED',
'SHALL', 'SHALL NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED', 'MAY',
and 'OPTIONAL' are to be interpreted as described in RFC 2119 [1]
and indicate requirement levels for compliant implementations.
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3. Requirements for Specification of Filters
The following requirements relate to the creation of filters (rules).
3.1 Common Syntax
A common set of constructs MUST be defined for the creation of rules.
There MUST be a common set of operations that follow a common syntax.
The user MUST be possible to define different rules for different
purposes using a common filtering mechanism.
3.2 Package Identification
A means is REQUIRED whereby the user may specify the package the
rules apply to.
3.3 Target URI
It MUST be possible for the watcher to indicate the target presentity
or presentity list to which a certain filter criteria is applied.
It MUST be possible to support filtering also in presence list
subscriptions.
Is MUST be possible to specify different filter criteria for
individual presentities than the other presence list members in a
presence list subscription case.
3.4 Notification Triggering
This chapter presents requirements for specifying the desired
conditions for when notifications are to be sent to the client.
The scope of the 'when' part is to allow a possibility for the user
to specify such rules for the notification triggering where the
criteria is based on the presence information, e.g., the value of the
status element.
The notification triggering criteria would override the default
trigger conditions of the server/service as defined in the package
when they are within the server's local policy constraints.
It MUST be possible to specify logical expressions based on the value
of elements defined in the package for the purpose of when to send
notifications. This covers expressions (tests) related to the change
of an element's value, and reaching a certain value of an element.
It MUST be possible to construct expressions that combine multiple
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tests.
3.5 Notification Content Limiting
This chapter presents requirements for specifying the content to be
sent in the notifications.
It MUST be possible for the watcher to specify the presence
information elements [2] (XML elements and/or attributes) to be
delivered in the notification. The specified elements MUST be able to
cover also extensions to PIDF formated presence information, see for
example [3].
E.g. the following two cases must be possible:
o The watcher MUST be able to define a criteria which allows the
complete tuple and all information within a tuple to be
transmitted.
o The watcher MUST be able to define a criteria which result
notifies to contain values only for defined attributes.
It MUST be possible to specify logical expressions based on the value
of elements defined in the package for the purpose of determining
what to send in the notification. The existence of an element SHOULD
be considered as a criterion.
It MUST be possible to construct expressions that combine multiple
tests.
4. Requirements for Uploading Rules (Operational Rules)
It MUST be possible for the watcher to upload the rules to the server
(notifier) and know the status - accepted or rejected.
4.1 SUBSCRIBE Method
Placing filtering rules in the body of the subscription MUST be
supported. Other means of delivering the filtering rules to the event
server MAY be supported. E.g. it should be possible for the rules to
be (permanently) stored in the server, as in a presence list case.
4.1.1 Retention of Filter Settings
The server MUST retain the uploaded filter setting for the duration
of the subscription.
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4.1.2 Changing Filter Settings
It MUST be possible to change the filter settings during a
subscription.
It MUST be possible for the watcher to reset the filter settings to
the service (server) defined default.
4.2 Server does not Support Filters
If the server does not support filters (the content type) then it
MUST be able to indicate so in a response.
4.3 Server does not Support Filter Settings
It MUST be possible for the server to explicitly indicate that it
does not support or understand the filter settings. This indication
MAY include a reason about the refusal of the filter settings.
4.4 Server can no Longer Support Filter Settings
The server MUST be able to terminate the subscription if the active
filter is no longer applicable due to a policy in the server.
5. Security Considerations
Further security requirements over [5] have not yet been identified.
6. Example Applications for Notification Filtering
1. A watcher wishes to get to know presentity's availability and
willingness for messaging (e.g. IM and MMS).
2. A watcher is interested in getting information about the
communication means and contact addresses the presentity is
currently available for communication.
3. A watcher requires a notification if the state of a buddy has
changed to 'open'.
4. A Subscriber only wants to be notified when the presentity's
location is Dallas or Fort Worth. The notification should include
the vehicle license, driver name, and city.
5. A Basic location tracking service requires notification when the
presentity's cell id changes. The notification should include the
cell id.
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7. Acknowledgements
The authors would like to thank Hisham Khartabil, Mikko Lonnfors,
Juha Kalliokulju, Aki Niemi, Jose Costa-Requena and Markus Isomaki
for their valuable input.
References
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
[2] Sugano, H., "CPIM Presence Information Data Format",
draft-ietf-impp-cpim-pidf-07.txt, December 2002.
[3] Schulzrinne, H., "RPIDS -- Rich Presence Information Data Format
for Presence Based on the Session Initiation Protocol (SIP)",
draft-schulzrinne-simple-rpids-01.txt, February 2003.
[4] Kiss, K., "Requirements for Presence Service based on 3GPP
specifications and wireless environment characteristics",
draft-kiss-simple-presence-wireless-reqs-02, February 2003.
[5] Rosenberg, J., "Session Initiation Protocol (SIP) Extensions for
Presence", draft-ietf-simple-presence-10.txt, January 2003.
[6] Roach, A., "Session Initiation Protocol (SIP)-Specific Event
Notification", RFC 3265, June 2002.
[7] Rosenberg, J., "A Watcher Information Event Template-Package for
the Session Initiation Protocol (SIP)",
draft-ietf-simple-winfo-package-05.txt, January 2003.
Authors' Addresses
Tim Moran
2800 Britt Drive
Argyle, Texas 76226
USA
Phone: +1 972 849 8821
EMail: tl_moran@att.net
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Sreenivas Addagatla
Nokia
6000 Connection Drive
Irving, Texas 75039
USA
Phone: +1 972 374 1917
EMail: sreenivas.addagatla@nokia.com
Eva Leppanen
Nokia
P.O BOX 785
Tampere
Finland
Phone: +358 7180 77066
EMail: eva-maria.leppanen@nokia.com
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