The QA4 language applied to robot planning

Abstract

This paper introduces an implemented version of a problem-solving language called QA4 (Question Answerer 4) and illustrates the application of that language to some simple robot problems. This application is especially appropriate, because the QA4 language has features that are recognized as useful for problemsolving programs; these features include built-in backtracking, parallel processing, pattern matching, and set manipulation. Expressions are put into a canonical form and stored uniquely, so that they can have property lists. A context mechanism is provided, so that the same expression can be given different properties in different contexts. The QA4 interpreter is implemented in LISP and can interface with LISP programs. The language is especially intended to be useful for research leading to program verification, modification, and synthesis, to semantically oriented theorem proving, and to various forms of robot planning.