Macro control languages and decision procedures for COCOLOG

Abstract

The control of a discrete event system is handled in the COCOLOG logic control system by use of an extra-logical representation of the control laws in terms of conditional control rules (CCRs); these are condition-action pairs in which the conditions are mutually exclusive and exhaustive formulas in the language (/spl Lscr//sub k/) at the instant k. Such formulas are tested for deducibility from Th/sub k/, the current control theory, and once the unique deducible formula is found, the associated control action is applied to the system. The simplicity of /spl Lscr//sub k/ leads to even the most basic concepts having a complex expression as well formed formulas in /spl Lscr//sub k/. Furthermore, the triggering of elementary control actions often depends upon complex nested sets of conditional control formulas (CCFs) expressed in /spl Lscr//sub k/. In response to this set of problems, this article presents the foundations for (i) a theory of the expression of complex predicates and functions in terms of simple macro language symbols which can be defined in an extended language /spl Lscr//sub k//sup +/, and (ii) the construction of recursive systems of simple macro actions to express complex control actions.