Presence information
In computer and telecommunications networks, presence information conveys availability and willingness of a user (called a presentity) to communicate. A user's client provides presence information to presence service to be stored and distributed to other users (called watchers) to convey its communication state. Presence information has wide application in voice over IP and instant messaging.
Presence state
A user client may publish a presence state to indicate its current communication status. This published state informs others that wish to contact the user of their availability and willingness to communicate. The most common use of presence today is the status indicator displayed on most instant messaging clients. A more simple everyday example is the 'on-hook' or 'off-hook' state of a telephone receiver, resulting in a distinctive ring tone for caller. Some states that offer extended information on the user's availability are "free for chat", "away", "do not disturb", and "out to lunch", which are often seen on many modern instant messaging clients. Rich information such as user mood and location may be also included. Presence is different from traditional 'on-hook' telephone status in that it deals with the user not the device (you want to talk to a person, not to a telephone).
MPOP and presence by observation
Presence becomes interesting for communication systems when it spans a number of different communication channels. The idea that multiple communication devices can combine state, to provide an aggregated view of a user's presence has been termed Multiple Points of Presence (MPOP). MPOP becomes even more powerful when it is automatically inferred from passive observation of a user's actions. This idea is already familiar to instant messaging users who have their status set to "Away" (or equivalent) if their computer keyboard is inactive for some time. Extension to other devices could include whether the user's cell phone is on, whether they are logged into their computer or perhaps checking their electronic calendar to see if they are in a meeting or on vacation. For example, if a user's calendar was marked as out of office and their cell phone was on, they might be considered in a "Roaming" state.
MPOP status can then be used to automatically direct incoming messages across all contributing devices. For example "Out of office" might translate to a system directing all messages and calls to the user's cell phone. The status "Do not disturb" might automatically save all messages for later and send all phone calls to voicemail.
XMPP, discussed below, allows for MPOP by assigning each client a "resource" (a specific identifier) and a priority number for each resource. A message directly to the user's ID would go to the resource with highest priority, although messaging a specific resource is possible by using the form user@domain/resource.
Watchers
Users have the potential to publish different presence states depending on who the communicator (or watcher) is. A worker may only want colleagues to see detailed presence information during office hours, for instance. Some users may want to only publish information to a select few. Basic versions of this idea are already common in instant messaging clients as a 'Block' facility, where users can appear as unavailable to selected watchers.
Commercial products
Presence, particularly MPOP, requires collaboration between a number of electronic devices (for example IM client, home phone, cell phone and electronic calendar). To date, presence has only seen wide scale implementation in closed, SPOP (Single Point of Presence, where a single device publishes state) systems. For presence to work in an MPOP environment, multiple devices must be able to intercommunicate.
2.5G and even more so 3G cell phone networks can support management and access of presence information services for mobile users cell phone handsets.
In the workplace, private messaging servers offer the possibility of MPOP within a company or work team.
Presence Information in the Business Community
Presence information is a growing tool towards more effective and efficient communication within a business setting. Presence information allows you to instantly see who is available in your corporate network, giving more flexibility to set up short term meetings and conference calls. The result is precise communication that all but eliminates the inefficiency of phone tag or email messaging. An example of the time saving aspect of presence information is a driver with a GPS, he/she can be tracked and sent messages on upcoming traffic patterns that in return save time and money. According to IDC surveys, employees “often feel that IM gives their workdays the kind of "flow" that they feel when sitting directly among their colleagues, being able to ask questions of them, and getting kind of quick responses that allow them to drive on to the next task."
With presence information, privacy of the users can become an issue. For example, when an employee is on his/her day off they are still connected to the network and have greater ability to be tracked down. Therefore, a concern of presence information is to determine how far the companies want to go with staying connected.
With all the potential advantages presence information has to offer it will only be a short time until all major corporations fully integrate presence information systems.
References:
“Presence Awareness Indicators - Where Are You Now?” Robin Good. September 23, 2004. http://www.masternewmedia.org/news/2004/09/23/presence_awareness_indicators_where.htm
Haag, Stephen. Cummings, Maeve. McCubbrey J, Donald. Pinsonneault, Alain. Donovan, Richard. Management Information Systems for the Information Age. Third Canadian Edition. Canada. McGraw-Hill, 2006.
XMPP, IMPS and SIMPLE
The implementation of a more complex presence system is limited by the amount of information that various devices exchange with each other.
There was and still is significat work done in several working groups on acheiving a standardization for presence related protocols:
Early activity was the creation of the CPIM spacification as an internet draft in Oct 2001.
This ran in parallel to create core requirements and specifications for managing presence with specific acknowledgement of the properties of mobile devices connected via radio access networks by the 3G Partnership Projects (3GPP, 3GPP2) and the Open Mobile Alliance (OMA).
An early standard was the IMPS-Enabler Release with a respective Suite of Client-Server and Server-to-Server Protocols in November 2002 by the OMA.
The XML-based XMPP or Extensible Messaging and Presence Protocol was designed and currently maintained by the Jabber Software Foundation. It is the base of the Jabber IM protocol, which is a robust and widely extended protocol, it is also the protocol used in the commercial implementation of Google Talk. In October 2004, the XMPP working group at IETF published the RFC documents 3920, 3921, 3922 and 3923, to standardize the core XMPP protocol.
Another standardization effort is based on SIP for Instant Messaging and Presence Leveraging Extensions (SIMPLE). SIMPLE specifies extensions to the SIP protocol which deal with a publish and subscribe mechanism for presence information and sending instant messages.
This proticol is used in the OMA Presence Simple V1.0 Enabler Specification as well as being the core - with proprietary extensions - of the MSN Messenger Instant Messaging Client and Service implementations.
The SIMPLE working group at the IETF is seeking to also standardizing this protocol.
The core effort to embed the concept of presence from ground up in 3G started out in November 2001 with a Technical Report on Presence (3GPP: TR 23.841). The consecutive respective publications were a requirements document (3GPP: TS 22.141), the Architecture and functional description document TS 23.141 and the Technical specification (3GPP: TS 24.141). When new developments occurred with regard to SIMPLE at IETF these were closely monitored and where required followed by update release versions of the technical report TR 23.841.
References
- Day, M., J. Rosenberg, and H. Sugano. "A Model for Presence and Instant Messaging." RFC 2778. February 2000.