54,333 research outputs found
Emulating Digital Logic using Transputer Networks (Very High Parallelism = Simplicity = Performance)
Modern VLSI technology has changed the economic rules by which the balance between processing
power, memory and communications is decided in computing systems. This will have a profound
impact on the design rules for the controlling software. In particular, the criteria for judging efficiency
of the algorithms will be somewhat different. This paper explores some of these implications through
the development of highly parallel and highly distributable algorithms based on occam and transputer
networks. The major results reported are a new simplicity for software designs, a corresponding ability
to reason (formally and informally) about their properties, the reusability of their components and some
real performance figures which demonstrate their practicality. Some guidelines to assist in these designs
are also given. As a vehicle for discussion, an interactive simulator is developed for checking the
functional and timing characteristics of digital logic circuits of arbitrary complexity
Rewriting Logic Semantics of a Plan Execution Language
The Plan Execution Interchange Language (PLEXIL) is a synchronous language
developed by NASA to support autonomous spacecraft operations. In this paper,
we propose a rewriting logic semantics of PLEXIL in Maude, a high-performance
logical engine. The rewriting logic semantics is by itself a formal interpreter
of the language and can be used as a semantic benchmark for the implementation
of PLEXIL executives. The implementation in Maude has the additional benefit of
making available to PLEXIL designers and developers all the formal analysis and
verification tools provided by Maude. The formalization of the PLEXIL semantics
in rewriting logic poses an interesting challenge due to the synchronous nature
of the language and the prioritized rules defining its semantics. To overcome
this difficulty, we propose a general procedure for simulating synchronous set
relations in rewriting logic that is sound and, for deterministic relations,
complete. We also report on two issues at the design level of the original
PLEXIL semantics that were identified with the help of the executable
specification in Maude
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