"Buddy lists" - a way of letting others know you're online and whether or not you're available for communication - are popular adjuncts to the instant messaging services offered by providers such as Yahoo, AOL, and Microsoft, among others. But instant messaging (IM) isn't the only medium that can profit from what's coming to be called 'presence': the ability to access realtime information about a person's status, communications capabilities, and preferences.
Presence is relevant to virtually every means of communication: not just instant messaging, but landline telephone numbers, mobile phones, VoIP phones, pagers, e-mail, home phones, and work phones. Capabilities include information such as "video is supported on my VoIP phone" and "voicemail is available on my cell phone." Preferences include things like "contact me at my mobile first, then try home." Characteristics include things like the GPS location of a cell phone, or the company providing an e-mail service. Taken together, this rich (and expandable) information-base enables powerful communications services. Services that really deliver the (as yet largely hypothetical) benefits of convergence: increased convenience; time- and money-savings; richer, more fluent, and more agreeable interactions.
When all is said and done, telecommunications is about connecting people. Unfortunately, the modern phone system doesn't do such a great job at this. According to industry estimates, only ten percent of calls actually end in productive conversation with the desired party; most calls hit voicemail, reach the called party at an inconvenient time, or go unanswered. Multiple phone numbers make the problem worse. Many phone services, such as "find-me" and "follow-me," are aimed at improving this situation.
The fundamental challenge lies in the fact that the caller is always guessing when, where, and how to reach the desired party. Think of how much better the experience of calling would be if you could know how, when, and where to reach the person. Instead of wasting time on calls that don't succeed, you could know ahead of time whether the call will be successful. This is exactly what presence enables and is the reason why it is the best thing to happen to voice communications. While presence capabilities can be enabled by several technologies, session initiation protocol (SIP) - the IETF standard for managing sessions over IP networks - is well-suited to support presence because of its Internet focus, its compact format, and its extensibility.
Let me illustrate by describing some examples of the services that could be enabled by presence. Consider conference calling. Getting five busy people together for a conference call, even a short one, is extremely difficult. Coordinating a conference call involves calls to secretaries, e-mails, checking with calendar tools, and so on. Of course, just planning a conference doesn't mean it will happen, since last minute issues often arise, meetings go later than expected, etc.
Now consider a service that can determine the best time for the conference simply by checking the presence status of the people in the conference. It might work like this: you go to a web page and fill out a form with the names of the participants in the call. The service itself then will subscribe to the presence of those users. As a result, it will receive updates as those participants come and go, turn on and off their cell phones, and log in and out of their computers. When the service detects that all are available in one form or another, it launches a call to each, prompts them about the beginning of the conference, and then connects them to a conference bridge. The result is an automated conference setup that creates a conference at the first possible opportunity - all without human intervention.
Another potential new service relies on a cell phone's location as an attribute of presence. Imagine a service that automatically informs you of traffic jams as you drive home. The service subscribes to your cell phone's location. As you drive, the service checks local traffic information from the web. If it detects you are approaching traffic; the service calls your cell phone and informs you of an alternate route.
Another example of location-based presence: sales-force tracking. Large sales teams are constantly on the road, making it difficult for their managers to know where they are. Imagine an application that automatically listed the salespeople on the team, their location, and their availability at any given moment.
Another example of a new service presence could support is a modernized "attendant console." Attendant consoles are common on PBX systems; they let the operator (also called the attendant) see the phone status of every extension connected to the PBX. Unfortunately, these consoles are limited. They can only monitor phones connected to the PBX and the console itself must be attached to the PBX. Interestingly, you can view an attendant console as a simple form of presence as well. Consider the possibilities for this simple application when real presence is used. The console can be a PC application. It can monitor people, rather than devices (therefore including cell phone, work phone, and VoIP phone in the status), and can manage anyone in the world willing to publish their presence information. The console itself can be run from anywhere, and more than one console can run on the same body of people, or on a subset or superset, without coordination. Consider the mobility benefits - the console attendants can now work from home and still manage the phone system in the enterprise, even monitoring the status of company employees who are telecommuting.
As with any new technology, there are trade-offs involved. While presence information can be used to enable useful services like those described above, it can also be used for nuisance or even criminal purposes. Just as a sales manager can track the presence of a sales team, so can a stalker track their victim. Just as a traffic jam service can call you when you near an accident, so can a restaurant call you when you walk nearby, asking if you'd like to stop in for a sandwich.
As a result of these concerns, it becomes absolutely critical to build privacy into the system. The privacy requirements of a presence system grow exponentially with the scope of the information propagated by that system. In simpler terms, the more personal data available the more important it is to protect it. The way privacy is managed represents, in itself, a rich space for services. Simple privacy systems might require you to accept or reject every individual or system that wishes to subscribe to your presence. More complex ones might allow you to pre-grant or pre-deny certain people or groups, or even delegate your decisions. For example, a company may have a "default" accept and deny list. You can override this list by specifying a certain individual to explicitly allow or deny, but in the absence of any information, your presence service would use the information defined by your company.
