Notes on an information model for productuion rules exchange
Peter O. Denno · 2006
Production rules are rules used in production systems, sometimes called production rule engines.Production rule engines are commonly used to implement expert systems.This report describes an information model for the exchange of production rules and for description of the relationship of the rules to a data population.The report is a precursor to a standardization effort in the ISO 10303 suite of standards.The report takes the form of a standards document generally, but departs from that form in places to provide more userfriendly explanation. ScopeThis report provides guidance on two forms of data structure mapping: (1) mapping of production rules to EXPRESS-based data [1], and; (2) mapping of instances in an EXPRESS population to structures typically found in production rule systems.The EXPRESS information model which this report describes is provided in an appendix to this report.The information model provides:• information describing rules for their use with typical production rule software • information identifying the entity data type instances of a given EXPRESS population, and their attributes, that are subject to the rules• information identifying the disposition of the rules with respect to the organization that produced them• information providing logical grouping of rules • information identifying the production rule software, and its version, with which the rules are intended to be used• constraints concerning the form of rules Out of scope for the information model are:• provisions describing the syntax of rules with respect to particular production rule software• provisions describing the execution semantics of rules NISTIR 7363 2006 2 of 20 Definitions• atomic formula -a syntactic structure consisting of a predicate symbol of some arity n, and an n-tuple of terms• condition -an atomic formula, or negated atomic formula, in the premise of a rule Note: conditions serve as patterns used in the pattern matching process of a production rule engine• constant -a symbol that invariantly names a distinct object • function -a term-forming relation that maps from an n-tuple of argument to at most one object• ground fact -an atomic formula that is free of variables • interpretation -the assignment of objects from the domain to the appropriate constructs of a formal language Note: These assignments are made by a human.• object -the thing referred to by a symbol in an interpretation • population mapping -a mapping of data governed by an EXPRESS schema to working memory of a production rule engine• predicate -a sentence-forming relation among objects Note: A predicate is encoded as an atomic formula.A predicate (father-of henry peter) might read "Henry is the father of Peter."• predicate symbol -a name that refers to the form of a predicate • production memory -the internal representation of rules in a production rule system• row value -a sequence of values, none of which are row values • row variable -a variable naming a row value in the context of a substitution • substitution -a mapping from variables to terms • symbol -an atomic lexical structure • term -an expression denoting an object • variable -a symbol that, in the context of a substitution, names an object • working memory -the internal representation of asserted facts in a production rule system