The Need for Prioritised Alternation in a Programming Language

摘要

A programming language embodies a model for the abstraction of systems behaviour. The domain of software application has changed dramatically since the early days of programming, and continues to evolve. While there has recently been an awakening to the need to express concurrency, little respect has been paid to either prioritisation or pre-emption, despite their increasing relevance to modern applications. Arguments are presented for the incorporation of a prioritised alternation (when) construct, previously proposed by the author, in any programming language intended for the description of embedded systems. (This reflects the operation of hardware prioritised vectored interruption.) It is further argued that prioritisation must apply to events alone and must be declared in advance as the context for an alternation. Comments will be made, and discussion invited, with regard to the semantics of both prioritisation and its composition.