The SIP Servlet API is similar in nature to the HTTP Servlet API, but there are some important differences. HTTP servlets run only on origin servers. In SIP, proxy servers play a much bigger role, as do application servers which initiate requests. As such, SIP servlets must be able to run on these other server types. This requires the ability to respond to requests, proxy requests, and initiate new requests.
Emphasis is on simplicitly and minimality rather than completeness.
This list of requirements is not necessarily complete and neither will all items be addressed by version 1.0. In particular we do not expect to define SIP servlet mappings, deployment descriptors, and file formats in version 1.0. We intend to define the API in a progression of specifications which address the requirements in an incremental fashion. This is done to ensure timely delivery of the API as well as in order to gain experience with some of the more advanced features prior to standardization. Please note that while the ability to proxy is central to SIP services, we make no assumption about whether this functionality is provided for servlets generally or for SIP servlets specifically.