\subsection{Control Predicates}

This section describes predicates to control the forward chaining
search strategy and truth maintenance operations.

\gloss{pfcSearch(P)}

This predicate is used to set the search strategy that \pfc\ uses in
doing forward chaing.  The argument should be one of
{direct,depth,breadth}.

\gloss{pfcTmsMode(Mode)}

This predicate controls the method used for truth maintenaance.  The
three options are {none,local,cycles}. Calling pfcTmsMode with an
instantiated argument will set the mode to that argument. 
\begin{itemize}

\item {\bf none} means that no truth maintenance will be done.

\item {\bf local} means that limited truth maintenance will be done. Specifically, no cycles will be checked.

\item {\bf cycles} means that full truth maintenance will be done,
including a check that all facts are well grounded.

\end{itemize}


\gloss{pfcHalt}

Immediately stop the forward chainging process.

\gloss{pfcRun}

Continue the forward chainging process.

\gloss{pfcStep}

Do one iteration of the forward chainging process.

\gloss{pfcSelect(P)}

Select next fact for forward chaining (user defined)

\gloss{pfcWarnings\\pfcNoWarnings}