Consider a queue abstract data type. It will have a 1) data structure
for holding tokens and 2) functions for inserting/retrieving tokens
in/from the data structure.
In fact, since a queue is used within a queuing system, we will
expand our definition of operators to include 1) a generator for
tokens, 2) a salvager of tokens, 3) a server, and 4) fork and join
operators.
Thus, our queuing system ADT can be used to create an entire system
of queues, servers, and token generators to model a system (e.g. a
DSP) at an uninterpreted (i.e. non-functional) level.
