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SOTAs: The Telephony Code: Page 9 of 12

We found the call-handling, conferencing, call-recording and IM/presence functions more than suitable for most purposes. Moreover, Sphericall is the only Web services offering that has a sufficiently comprehensive interface at this time; none of the other implementations that we looked at were as broadly usable.

Sphere has also implemented the most complete session management model, with support for asynchronous bi-directional communications over the SOAP channel. Sphere uses semi-permanent session identifiers to maintain long-term state across transactions, coupled with a client-side "fetchEvents" function. In this model, the client opens a connection, ask for any new events that are associated with the session, and then enters a timeout condition while waiting for event messages to arrive. If no notifications are received within a specified interval, the client will eventually timeout, and then reconnect with the server to restart the process. Cumulatively, this provides for bi-directional asynchronous session-level event messaging over SOAP, something none of the other implementations we saw offers.

A couple of other interesting features in the Spherical Web services implementation are worth noting. For one, presence and status information can be set through the Web services interface, meaning that you can have your application change the user's call status automatically--for example, changing an operator's status to reflect the fact that she is talking to a customer whenever she releases a call from an incoming queue. Also, the Sphericall IP PBX has a feature called "forwarding profiles," which allow for user-defined call routing, and those features are also partially exposed through the Web services interface.

Finally, Sphere provides a simulation server that can be used for offline development and testing; this will prove extremely useful for most in-house developers. Overall, the Spherical Web services interfaces is pretty comprehensive, and is by far the most com-plete offering we saw.

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