SIMPLE WG K. Kiss
Internet-Draft E. Leppanen
Expires: November 4, 2003 H. Khartabil
Nokia
May 6, 2003
Requirements for Filtering of Watcher Information
draft-ietf-simple-winfo-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
watcher information subscriber (client) may select specific
information to be received in the watcher infomation notification
sent by the notifier (server). The purpose is to limit the content so
that only essential information 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 Content Limiting . . . . . . . . . . . . . . . 4
3.4.1 Status . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.4.2 Event Causing the Transition . . . . . . . . . . . . . . . . 4
3.4.3 Expiration . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.4.4 Duration of Subscription . . . . . . . . . . . . . . . . . . 5
3.4.5 Selected Watchers . . . . . . . . . . . . . . . . . . . . . 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 . . . . . . . . . . . . . . . . . . 5
4.2 Server does not Support Filters . . . . . . . . . . . . . . 5
4.3 Server does not Support Filter Settings . . . . . . . . . . 5
4.4 Server can no Longer Support Filter Settings . . . . . . . . 6
5. Security Considerations . . . . . . . . . . . . . . . . . . 6
6. Example Applications for Notification Filtering . . . . . . 6
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6
References . . . . . . . . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 7
Intellectual Property and Copyright Statements . . . . . . . 8
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1. Introduction
SIP event notification is described in [4]. 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 [3] (user presence) and [5] (watcher
information).
The watcher information refers to the set of users subscribed to a
particular resource within a particular event package. Watcher
information changes dynamically as users subscribe, unsubscribe, are
approved, or rejected. A client can subscribe to this information.
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 [2].
The Internet Draft describing the watcher information template
package [5] mentions the possibility for filtering. Accordingly, the
SUBSCRIBE request may contain a body for filtering the watcher
information subscription. However, the definition of filtering has
been left out of the scope of the Internet Draft.
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 client 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 client may specify the package the
rules apply to.
3.3 Target URI
It MUST be possible for the client to indicate the target user to
which a certain filter criteria is applied.
3.4 Notification Content Limiting
This chapter presents requirements for specifying the content to be
sent in the notifications.
It MUST be possible for the client to specify the watcher XML
elements [6] to be delivered in the notification.
It MUST be possible to specify logical expressions based on the value
of elements defined in the template-package for the purpose of
determining what to send in the notification.
It MUST be possible to construct expressions that combine multiple
tests.
3.4.1 Status
The client MUST be able to indicate to the server to include only
those watchers in the notifications which are in a specific status.
3.4.2 Event Causing the Transition
The client MUST be able to indicate to the server to include only
those watchers in the notifications which are transitioned in their
current status because of a specific event.
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3.4.3 Expiration
The client MUST be able to indicate to the server to include only
those watchers in the notifications which have subscription lifetime
higher than (less than) a specific amount of seconds.
3.4.4 Duration of Subscription
The client MUST be able to indicate to the server to include only
those watchers in the notifications which are subscribed for a
duration higher than (less than) a specific amount of seconds.
3.4.5 Selected Watchers
The client MUST be able to indicate to the server to include only
certain watchers (e.g. watchers from a particular domain, specific
watchers defined by the filters) in the notifications.
4. Requirements for Uploading Rules (Operational Rules)
It MUST be possible for the client to upload the rules to the server
and know the status - accepted or rejected.
4.1 SUBSCRIBE Method
Placing filtering rules in the body of the subscription MUST be
supported.
4.1.1 Retention of Filter Settings
The server MUST retain the uploaded filter setting for the duration
of the subscription.
4.1.2 Changing Filter Settings
It MUST be possible to change the filter settings during a
subscription.
It MUST be possible for the client 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
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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 [3] have not yet been identified.
6. Example Applications for Notification Filtering
1. A presentity wishes to see who has subscribed to their presence.
The presentity only wishes to see information for subscribers who
are co-workers.
2. A presentity makes subscription to get information about active
watchers.
3. A presentity makes subscription to get information about defined,
new or unauthorised watchers.
4. A presentity requests history information of watchers.
7. Acknowledgements
The authors would like to thank Jonathan Rosenberg, Tim Moran and
Juha Kalliokulju 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] Kiss, K., "Requirements for Presence Service based on 3GPP
specifications and wireless environment characteristics",
draft-kiss-simple-presence-wireless-reqs-02, February 2003.
[3] Rosenberg, J., "Session Initiation Protocol (SIP) Extensions for
Presence", draft-ietf-simple-presence-10.txt, January 2003.
[4] Roach, A., "Session Initiation Protocol (SIP)-Specific Event
Notification", RFC 3265, June 2002.
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[5] Rosenberg, J., "A Watcher Information Event Template-Package for
the Session Initiation Protocol (SIP)",
draft-ietf-simple-winfo-package-05.txt, January 2003.
[6] Rosenberg, J., "An Extensible Markup Language (XML) Based Format
for Watcher Information",
draft-ietf-simple-winfo-format-04.txt, January 2003.
Authors' Addresses
Krisztian Kiss
Nokia
P.O. Box 100
33721 Tampere
Finland
Phone: + 358 50 4835363
EMail: krisztian.kiss@nokia.com
Eva Leppanen
Nokia
P.O BOX 785
Tampere
Finland
Phone: +358 7180 77066
EMail: eva-maria.leppanen@nokia.com
Hisham Khartabil
Nokia
P.O. Box 321
Helsinki
Finland
Phone: +358 7180 76161
EMail: hisham.khartabil@nokia.com
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