The Core Language

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The Core Language

Following the conventions of Prolog, variables begin in upper case. Constants, functors and predicates begin in lower case. Anonymous variables are denoted by underscores.

Definition 1578

A term is defined inductively as follows:
$\begin{smallenum} \item a variable is a term \item a constant is a term \item i... ...For convenience, we use f/n to denote a functor f with arity n.\end{smallenum}$

Definition 1579

A formula is defined inductively as follows:
$\begin{smallenum} \item if p is an n-ary predicate symbol and $T_{1}, T_{2}, ...... ... p with arity n. \item if F is a formula, so is ({\bf not} F). \end{smallenum}$

Definition 1580

A literal is an atom or the negation of an atom. A positive literal is an atom. A negative literal is the negation of an atom.

Definition 1587

If q is a positive literal, p₁, p₂, ..., p_n are literals, $n\geq0$ , then

q :- p₁, p₂, ..., p_n.

is a rule. Atom q is called the head, and p₁, p₂, ..., p_n combined is called the body of this rule.

Du Li
8/25/1999