CCAL: an interpreted language for experimentation in concurrent control

Concurrent Control Abstraction Language, CCAL, is an interpreted language which provides no particular control regime to the user. CCAL instead supports five primitive operations which manipulate an abstract model of inter-procedural control. This model is intrinsically concurrent, and the user is allowed to construct high-level concurrent control operations from the primitives (hence, control abstraction). The primary use of CCAL is as a vehicle by which rapid prototyping of application specific control forms may be done and as a tool for the construction and evaluation of novel control forms, especially control forms for highly concurrent and distributed systems. The CCAL interpreter is implemented as a distributed program on a network of Vaxen and Sun-3 workstations under 4.2bsd and 4.3bsd Unix1. CCAL programs appear as multi-process programs in a shared memory system. Both true and apparent concurrency are possible. This paper describes the control abstraction facilities offered by the CCAL interpreter, its use, and implementation strategies in the distributed environment.