TELOS, A Language for Building Well-Structured AI Models

TELOS is an attempt to provide powerful abstraction mechanisms and other structuring facilities within a language that provides the special capabilities needed for AI research. TELOS includes PASCAL as a subset and also is implemented in PASCAL. A full description is available in [1] and [2], Like most other AI languages, TELOS includes facilities needed for experimentation with large stores of general knowledge, tentatively modifi-able and associatively referenceable, and with various planning and reasoning strategies. However , in contrast to other AI languages whose design has focused on building in certain powerful high-level constructs, the design of TELOS has focused on building in powerful abstraction mechanisms with which these particular high-level constructs, as well as numerous others, can be defined and implemented with reasonable ease. The usefulness of abstraction in all kinds of human intellectual activity has long been observed , and programming is certainly no exception. Only recently, however, have programming languages begun to appear with features specifically designed to facilitate abstraction of the several different kinds needed in the programming process, in particular, data abstraction and control abstraction as well as procedural abstraction. TELOS implements a set of data, control, and procedural abstraction mechanisms specifically tailored to AI requirements. An AI programmer might use TELOS capsules to define data types ranging from low-level lists (of the kind built into most other AI languages) to theoretically significant data structures. Such high-level abstract type definitions might implement , for example, case-slotted prototypes (frames), concept-dependency graphs, or production "conditionals". By emphasizing abstraction mechanisms rather than high-level constructs (e.g., frames as a basic data type, as in KRL), it has been possible to minimize theoretical bias in the language. Consequently TELOS should be usable for investigation of numerous competing theories, for example, in the area of knowledge representation. The control abstraction capabilities provided in TELOS enable convenient user definition of the novel kinds of control regimes which are investigated in AI research, that is, those which realize alternative problem-solving strategies. Just as TELOS capsules localize data representation details , TELOS "overseers" localize interprocess control-transfer and communication details needed to realize a desired control regime. An AT programmer might use TELOS overseers to define control regimes ranging from blind, depth-first backtracking (of the kind built into many recent AI languages) to quasi-parallel processing to sophisticated planning strategies. Features are provided which enable the procedures and processes controlled by an overseer to be identified …