KRSS Reference

Introduction

KRSS is an acronym of Knowledge Representation System Specification. You can find the exact specification at http://www.bell-labs.com/user/pfps/papers/krss-spec.ps. Note that this is an abstract specification and any particular system that utilizes it is not required to accept/recognize all of the specified constructs.

Basic Constructs

KRSS uses Lisp-like syntax. Each top level expression is refered to as 'statement'.
Following is a formal grammar of the krss format recognized by BOR:

krrs-file ::= <tbox-stmt>* end-tbox? <abox-stmt>* end-abox? ;;

tbox-stmt ::= (primitive-concept <concept-name>)
            | (define-primitive-concept <concept-name> <concept-expr>)
            | (define-concept <concept-name> <concept-expr>)
            | (subrole <subrole-name> <super-role-name>)
            | (transitive <role-name>)
            | (enum <enum-datatype-name> <member-name>+)
            | (range <role-name> <datatype-name>)
            ;;

concept-expr ::= <concept-name>
               | (and <concept-expr>+)
               | (or  <concept-expr>+)
               | (not <concept-expr>)
               | (all  <role-name> <concept-expr-or-dataset-transcript>)
               | (some <role-name> <concept-expr-or-dataset-transcript>)
               | (none <role-name> <concept-expr-or-dataset-transcript>)
               | (at-least <integer> <role-name> <concept-expr-or-dataset-transcript>?)
               | (at-most  <integer> <role-name> <concept-expr-or-dataset-transcript>?)
               | (exactly  <integer> <role-name> <concept-expr-or-dataset-transcript>?)
               ;;

concept-expr-or-dataset-transcript ::=  |  ;;

abox-stmt ::= (instance <individual-name> <concept-expr>)
            | (related  <subject-name> <role-name> <object-name>)
            | (equal    <individual-name> <another-individual-name>)
            | (distinct <individual-name> <another-individual-name>)
            ;;

Comments

Note that whenever a krss source contains both a TBox and an ABox the former must preceed the later. In this case the presence of the separating `end-tbox' statement is mandatory.
BOR accepts also the shortcuts `pc', 'def-pc' and `def-c' in place of their longer equivalents primitive-concept, define-primitive-concept and define-concept.
Each concept must have at most one definition. Use of concept without definition causes the concept to be implicitly defined as primitive concept without definition.

Example

(enum SkinColor (white black yellow red albino))
(enum EyeColor  (blue brown green hazel black albino))

(range skin-color SkinColor)
(range eye-color  EyeColor)
(range age Int)

(def-c indian (some skin-color "red"))
(def-c adult (some age "[18,+oo)"))
(def-c mother-of-an-adult-blue-eyed-indian
         (some has-child (and adult indian (some eye-color "blue"))))
(def-c target mother-of-an-adult-indian)

end-tbox