Proposed Enhancements

It was agreed that any enhancement should be properly justified by stating reasons for enhancements and should meet requirements for E according to work item definition. It was decided that each extension should have a clearly defined notion of upward compatibility with respect to standard and should justify it. A list of proposed enhancements was discussed:

• time

• priorities

• compound events

• real parallelism

• typed gates

• generalized termination

• generalized enabling

• probabilities

• suspend/resume (interrupt)

• loop statement

• ifthenelse and default

• Dynamic configuration

• processes as values

• parallel operator on values

• binary synchronisation

The following conclusions were reached on these enhancements:

• Time enhancements were discussed and considered necessary. The two existing proposals will be evaluated during the next period.

• Priorities may be a desirable feature for E. Feasible solutions have to be investigated. At least one proposal exists.

• Some type of compound event or typed interaction is considered to be desirable. A proposal for behaviour-based compound events exists but similar results may be obtainable on the basis of typed tagged gates.

• Real parallelism is left for further study.

• Modularity. Two proposals exist. The necessity of modularity is unanimously recognised.

• Typed gates. General support for gate typing exists, however there was considerable discussion of detail, especially on the following question: polymorphic gates, names versus structural gate equality, compatibility with untyped gates.

• Generalized termination. There was considerable support for the concept of generalized termination and enabling. A proposal exists, however improvements are being considered.

• Probabilities. These are left for further study.

• Suspend/resume operator. It was felt that the operator could be useful, and the Committee is waiting for further evidence of its need and use, especially in the form of additional examples.

• Loop, ifthenelse, dynamic configuration, processes as values, PAR-operator on values, binary synchronisation. These all appear to be useful enhancements.