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sav08:polynomial_algorithm_for_horn_clauses [2008/03/12 14:10]
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sav08:polynomial_algorithm_for_horn_clauses [2008/03/12 15:59] (current)
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Such clause is either of the form $\{p\}$ where $p \in V$ is a variable, or $\{\lnot p\}$ for $p \in V$, or of the form $\{\lnot p_1, \ldots, \lnot p_n, q\}$ for $n \ge 1$, that is $p_1 \land \ldots \land p_n \rightarrow q$. Such clause is either of the form $\{p\}$ where $p \in V$ is a variable, or $\{\lnot p\}$ for $p \in V$, or of the form $\{\lnot p_1, \ldots, \lnot p_n, q\}$ for $n \ge 1$, that is $p_1 \land \ldots \land p_n \rightarrow q$.

-The following algorithm eliminates clauses of the form $\{p\}$, keeping only clauses that have at least one assumption.+The following algorithm eliminates clauses of the form $\{p\}$, keeping only clauses that have at least one negative literal.

To check satisfiability of a set of Horn clauses: To check satisfiability of a set of Horn clauses: