Introducing the Preference Control Primitive: Experience with Controlling Nondeterminism in Ada

This paper suggests the addition of "preference control" to Ada. The expressive power of Ada can be increased by the use of control primitives within the nondeterministic construct, the select statement which we have classified as: private control, consensus control and hybrid control. This paper demonstrates the need for what we have classified as preference control. Examples in Ada requiring preference control will be described; then their solutions with and without the use of preference control primitives will ve described and analyzed with respect to original Ada design specifications and software engineering principles.