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\ ' \ \ \ \ NEW PROGRAMMING LANGUAGES FOR AI RESEARCH BY DANIEL G. BOBROW AND BERTRAM RAPHAEL* New directions in Artificial Intelligence research have led to the need for certain nove~ features to be embedded in programming languages. This paper gives an overview of the nature of these features, and their implementation in four principal families of AI Languages: SAIL; PLANNER/CONNIVER; QLISP/INTERLISP; and POPLER/POP-2. The programming features described include: new ~ types and accessing mechanisms for stored expressions; more flexible control structures, including multiple processes and backtracking; pattern matching to allow comparison of data item with a template, and extraction of labelled subexpressions; and deductive mechanisms which allow the programming system to carry out certain activities including modifying the data base and deciding which subroutines to run next using only constraints and guidelines set up by the programmer. ~ertram Raphael is at the Stanford Research Institute, Menlo Park, California. REPORT NO. CSL-73-2 DATE August 20, 1973 DESCRIPTORS XEROX PALO ALTO RESEARCH CENTER 3180 PORTER DRIVE/PALO ALTO/CALIFORNIA 94304 TABLE OF CONTENTS PAGE CHAPTER I INTRODUCTION 2 CHAPTER II LANGUAGES COVERED 4 CHAPTER III SPECIAL FEATURES COMMON TO THE NEW LANGUAGES 7 A Data Types 7 B Control Structures 9 C Pattern Matching 13 D Deductive Mechanisms 14 CHAPTER IV DIFFERENCES BETWEEN THE NEW LANGUAGES 16 A Data Types and Storage Meohanisms 16 1 SAIL 16 2 PLANNER/CONNIVER 18 3 QLISP/INTERLISP 20 4 POPLER 21 B Control Structures 22 1 SAIL 22 2 PLANNER/CONNIVER 23 3 INTERLISP/QLISP 25 4 POPLER/POP-2 28 C Pattern Matching 29 1 SAIL 29 2 PLANNER/CONNIVER 29 3 QLISP/INTERLISP 31