Presence Requirements

This is a high level design for implementing the SIP SIMPLE standards related to presence and presence.winfo event packages into the SIP SIMPLE client that achieves the following goals:

  1. Manages a Contacts List
  2. Controls the presence information published by a SIP account, handles the Subscriptions and Notifications for the Contacts
  3. Manages an Icon (a small size picture of the end user using the client)
  4. Managed the Policy that described who has access to what part of the published PIDF

The design requires a Presence Agent and an XCAP server serving the domain of the SIP account for which this functionality is desired.

Contacts List

Contacts List contains is a list of discrete contacts displayed by the GUI. It must be managed by the SIP client at a global level above the individual SIP account level.

The Contacts List is organized into Groups. The SIP client maintains this central Groups List by merging all found groups on local and remote storage(s) and populates each group with all contacts found for them.

Some contacts are marked to Subscribe to them for Event: presence. Based on received Notify messages for Event: presence, each Contact has a presentity attribute that contains its own published information as pidf xml payload, the GUI can display attributes of it.

The following presence related payloads as used to generate the presentity payload used for publish:

  • Presence Data Model RFC4479
  • Rich Presence Extensions RFC4480
  • Contact Information for the Presence Information Data Format RFC4482
  • User Agent Capability Extension to Presence Information Data Format RFC5196

Same Contact may end up belonging to different Groups if the same SIP address is stored on multiple XCAP servers in different groups.

The SIP client builds the Contacts List by concatenating the individual lists stored locally or on the resource-lists documents stored on the XCAP server corespondent to each SIP account.

When a Contact is added/modified/deleted the corespondent remote XCAP storage documents are also updated. The remote storage is set per Contact in the Add/Edit Contact dialog of the SIP client. This remote server storage is used for initializing the locally cached Contacts List between restarts and to synchronize changes between multiple SIP UAs configured for the same SIP account.


Each SIP Account has settings in the middleware that affect the way it interacts with its correspondent Contacts

  • Subscribes to information related to who has subscribed to its own presence information and generate a policy document that is used for subsequent subscriptions and notifications by the Presence Agent
  • Stores its data into the XCAP server corespondent with the SIP account or locally if no XCAP server is available


If account.xcap is enabled

  • If account.xcap.xcap_root is not set, locate XCAP root by doing a DNS TXT lookup for
  • GET XCAP application xcap-caps
  • GET XCAP application xcap-directory
  • For all supported applications returned by above step, GET their files and cache them locally

If Icon application is enabled

  • GET the previous icon using HTTP request
  • Refresh the location of the XCAP server based on DNS TTL


If account.presence.enabled is True

  • Send Publish with the current pidf if pidf_manipulation is not set, let the user change his state manually if pidf_manipulation is set

If account.xcap is enabled and account.presence.enabled is True

  • Initialize the Contacts List by using the content of the XCAP document resource-lists, filename index. Initialize the Subscriptions List using the Contacts marked for Subscribe to Presence

If account.xcap is enabled and account.presence.use_rls_services is enabled

  • Put the content of Subscription List initialized above to the XCAP document rls-services identified by SIP URI account-buddies@domain.

PIDF manipulation

  1. Add menu item with Offline status that brings up dialog window with Presence Activity and Note to be displayed while offline.
  2. Add a reminder icon on main interface so that we know we have set this offline status


If account.xcap is enabled and account.xcap.use_xcap_diff is enabled

  • Sent Subscribe for Event: xcap-diff to the account own SIP address

If account.presence.enabled is True

  • Send Subscribe for presence.winfo to the account own SIP address

If account.presence.use_rls_services is True

  • Send one Subscribe for Event: presence, and header Supported: eventlist to sip:account-buddies@domain


  • For each contact in the Subscriptions List send individual Subscribe for Event: presence


  • On Notify for Event: xcap-diff that a supported XCAP document has been changed by other SIP UA GET the new document
  • On Notify for Event: presence update the presentity of affected Contacts
  • On Notify for Event: presence.winfo trigger notifications end user to update its policy

Each individual contact list stored in a resource-lists document is indexed by a unique SIP URI, a random SIP URI must be generated for Contacts that do not have a real SIP URI and we must mark the contacts that we want to Subscribe to for presence information. Additional, one can store full names and other attributes related to remote recipient by using extensions to PIDF for contact information (cipid extension).

Policy change

  • Based on Notify for Event: presence.winfo alert the user about new watchers
  • If account.xcap is enabled PUT pres-rules document on the XCAP server

Transformations are required to support the following functionality:

  1. First degree watchers - access to entire PIDF
  2. Second degree watchers - access to subset of PIDF
  3. Third degree watchers - access to basic presence online/offline


The SIP client must be notified by the middleware when a network event related to Presence occurs:

  1. Watcher list has changed
  2. Account has activated/deactivated to update the Contacts List
  3. Presence information of a Contact has changed
  4. A conflict exists between the server version and the local version of an XCAP document

Each Contact can publish properties related to his device capabilities (e.g. chat, audio, video). This is conveyed via caps extension to pidf and can be used to drive the contextual menu presented for each Contact related to what kind of action can be initiated to it.


  1. Display and manages the Contacts List
  2. Display attributes of the Presence information of each Contact
  3. Manage the content of the Policy document
  4. Update the Icon of the SIP account


Publishing end-point:

  1. Generate a new random filename: XYZ
  2. Build URL
  3. PUT the new icon document to XCAP server
  4. Update <icon> element of pidf and PUBLISH new pidf
  5. DELETE any previously uploaded icon file

Subscribing end-point:

  1. Parse <icon> element of pidf cipid extension received in Notify
  3. Cache picture until next Notify with diferent <icon> element is received

The icon is common across all accounts, it must be put on all XCAP servers for all active accounts.


All PIDF attributes that can be published must register themselves with the Policy manager. This Policy Manager renders these PIDF attributes in a Window where the user can associate the attributes with Contacts that subscribe to his presentity.

Presence Design

  1. Contact management
    1. local vs xcap (resourcelist) storage
  2. Incoming presence
    1. Subscribe to presence
    2. Subscribe to dialog-event
    3. RLS Services document management
  3. Outgoing presence
    1. Publish presence, dialog-event
    2. PIDF-manipulation
    3. Subscribe .winfo
    4. Pres-rules, dialog-rules
    5. Icon

Published items

  1. presence activity
  2. presence note
  3. icon
  4. location URL
  5. display name
  6. idle status (keyboard idle)
  7. privacy information
  8. time offset from UTC
  9. device capabilities

Design notes

  • XCAPManager (DONE)
    • offers high-level API for accessing different types of resources (resource-lists, rls-services, pres-rules, dialog-rules, pidf)
    • keeps cached copies of XCAP-stored files in case there is lack of connectivity
    • keeps journal with high-level described changes made to files (in case of lack of connectivity, these will be retried later)
    • subscribes to xcap-diff so it can be informed of changes to xcap files
  • Contacts Manager (DONE except subscriptions which are work in progress)
    • per-account
    • communicates with XCAPManager to find out information about the contacts
    • integrate with contact list: contacts should have attributes with various information that can be retrieved by subscribing to presence and dialog events (tree structure most likely, rather than having all attributes at the same level)
    • solve conflicts and aggregate information from multiple publishing agents
  • Presence Manager
    • offer API for fine-grained control of published info (pres-rules and dialog-rules)
    • be able to understand any valid policy because it can be changed by another client and notify the application when the policy is changed
    • subscribe to .winfo of presence and dialog events and manage information about active, pending and blocked subscriptions (integrate with contact list)
    • notify user of new subscription requests
    • information published via presence and dialog events
    • accounts should have attributes which can store information to be published (probably similar to contacts)
    • accounts should publish this information automatically if configured to
    • manage persistent presence information via xcap pidf-manipulation
    • publish icon via xcap
    • estimated time of development: 1 weeks

contact-details.jpg (45.6 kB) Adrian Georgescu, 02/01/2010 12:56 am

BuddyList-Aggregation.png (109.4 kB) Adrian Georgescu, 02/01/2010 01:16 am

PresencePolicy.png (38.8 kB) Adrian Georgescu, 02/12/2010 10:26 am