Design representation structural domain

A model of design representation with three domains of description (Behavioral, Structural, and Physical) and multiple levels of abstraction. 

ThBR87] D.E. Thomas, R.L. Blackburn, J.V. Rajan, Linking the Behavioral and Structural Domains of Representation for Digital System Design, IEEE Trans. CAD, January 1987. 

The continuous-time representation has the same ambition events are allowed to take place at any point in the continuous domain of time. This is carried out by introducing the concept of variable event time that can be defined either globally or for each unit. For this purpose, additional variables are necessary to determine the timings of events. Since a major fraetion of the inactive event-time interval assignments is eliminated with the continuoustime approach, the resulting mathematical models require less computational effort for their solution of the associated scheduling task involved in design/retrofit problems. However, the mathematical models involved in the continuous-time approach may embed more complicated structures compared with their discrete-time counterparts. 

Language Usage. Following the conventions described in our model of representation, the ISPS behavioral domain description is maintained as a pure behavior, represented separately from the structure or physical information. That is, the use of a "+", or operator in ISPS only specifies that the operation must take place on the named values. It does not specify the actual functional units to be used for each of the operations, the memory units in which the values are to be stored, nor does it specify the order in which the operations will take place. Thus, the Workbench has the freedom to design any hardware and control sequence implementation with the proviso that the final implementation s behavior match that specified by the lexical data-flow ordering and the required (NEXT) ordering of the original behavior. 

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