A Formal Representation for Plans in the Programmers Apprentice

A p l a n calculus is presented which is being used to represent p r o g r a m s and a l i b ra ry of standard data and control abstractions in t h e p r o g r a m m e r ' s apprent ice . Important features of this formalism i n c l u d e : p rogramming language independence, additivity, v e r i f i a b i l i t y and mult ip le points of v iew. The logical foundations of t h e r e p r e s e n t a t i o n are specif ied formally using a situational ca l cu lus in wh i ch side ef fects and overlapping mutable data s t r u c t u r e s are accounted tor. The plan calculus is comparedwi th o t h e r fo rma l i sms , such as program schemas, and its advantages p o i n t e d ou t .