An Overview of KRL. AIM-293

This paper describes KRL, a Knowledge Representation Language designed for
use in understander systems. It outlines both the general concepts which
underlie our research and the details of KRL-0, an experimental
implementation of some of these concepts. KRL is an attempt to integrate
procedural knowledge with a broad base of declarative forms. These forms
provide a variety of ways to express the logical structure of the
knowledge, in order to give flexibility in associating procedures (for
memory and reasoning) with specific pieces of knowledge, and to control
the relative accessibility of different facts and descriptions. The
formalism for declarative knowledge is based on %2structured conceptual
objects%* with associated %2descriptions%*. These objects form a network
of %2memory units%* with several different sorts of linkages, each having
well-specified implications for the retrieval process. Procedures can be
associated directly with the internal structure of a conceptual object.
This %2procedural attachment%* allows the steps for a particular operation
to be determined by characteristics of the specific entities involved.

The control structure of KRL is based on the belief that the next
generation of intelligent programs will integrate data-directed and
goal-directed processing by using multi-processing. It provides for a
priority-ordered multi-process agenda with explicit (user-provided)
strategies for scheduling and resource allocation. It provides
%2procedure directories%* which operate along with %2process frameworks%*
to allow procedural parameterization of the fundamental system processes
for building, comparing, and retrieving memory structures. Future
development of KRL will include integrating procedure definition with the
descriptive formalism.