Telecommunication services are often implemented to maintain their state in persistent storage. The application logic program
then has no state variables of its own; it is seeded with a state depending on call context. Superficially, this contradicts
the notion of extended state machines as they are defined by SDL-processes, where the state is part of the state machine.
This paper presents an approach to separate state from program logic that is transparent to the SDL designer. This approach
has been implemented in the SITE SDL runtime system in co-operation with Siemens, Berlin.
We would like to thank our partners at Siemens, in particular Mr. Andreas Vogel, for the numerous ideas and suggestions that
lead to the technology described in this paper.