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\section{library(increval): Incremental dynamic predicate modification}

\label{sec:increval}

\begin{tags}
    \tag{Compatibility}
XSB
\end{tags}

This module emulates the XSB module \const{increval}. This module serves two
goals: (1) provide alternatives for the dynamic clause manipulation
predicates that propagate into the incremental tables and (2) query the
dynamically maintained \textit{Incremental Depency Graph} (IDG).

The change propagation for incremental dynamic predicates. SWI-Prolog
relies in \predref{prolog_listen}{2} to forward any change to dynamic predicates to
the table IDG and \predref{incr_assert}{1} and friends thus simply call the
corresponding database update.\vspace{0.7cm}

\begin{description}
    \predicate[nondet]{is_incremental_subgoal}{1}{?SubGoal}
This predicate non-deterministically unifies Subgoal with
incrementally tabled subgoals that are currently table entries.

    \predicate[nondet]{incr_directly_depends}{2}{:Goal1, :Goal2}
True if \arg{Goal1} depends on \arg{Goal2} in the IDG.

\begin{tags}
    \tag{Compatibility}
: In XSB, at least one of Goal 1 or Goal 2 must be bound.
This implementation may be used with both arguments unbound.
\end{tags}

    \predicate[nondet]{incr_trans_depends}{2}{:Goal1, Goal2}
True for each pair in the transitive closure of
\verb$incr_directly_depends(G1, G2)$.

    \predicate[det]{incr_invalid_subgoals}{1}{-List}
\arg{List} is a sorted list (set) of the incremental subgoals that are
currently invalid.

    \predicate[semidet]{incr_is_invalid}{1}{:Subgoal}
True when \arg{Subgoal}'s table is marked as invalid.

    \predicate[det]{incr_invalidate_calls}{1}{:Goal}
Invalidate all tables for subgoals of \arg{Goal} as well as tables that
are affected by these.

    \predicate[det]{incr_invalidate_call}{1}{:Goal}
This is the XSB name, but the manual says \predref{incr_invalidate_calls}{1}
and the comment with the code suggests this is misnamed.

\begin{tags}
    \tag{deprecated}
Use \predref{incr_invalidate_calls}{1}.
\end{tags}

    \predicate{incr_table_update}{0}{}
Updated all invalid tables

    \predicate[det]{incr_propagate_calls}{1}{:Answer}
Activate the monotonic answer propagation similarly to when a new
fact is asserted for a monotonic dynamic predicate. The \arg{Answer} term
must match a monotonic dynamic predicate.
\end{description}