The ADA tasking model was intended to support the management of concurrency in a priority-driven scheduling environment. In this paper, we review some important results of a priority-based scheduling theory, illustrate its applications with examples, discuss its implications for the ADA tasking model, and suggest workarounds that permit us to implement analytical scheduling algorithms within the existing framework of ADA. This paper is a revision of CMU/SEI-88-TR-033. The most important revisions affect our discussion of aperiodic tasks and our analysis of how to support the priority ceiling protocol. A shortened version is also being presented at the 1989 ADA-Europe Conference.

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