jade.semantics.kbase.filters.std

Class HornClauseFilter

java.lang.Object

jade.semantics.kbase.filters.KBFilter

jade.semantics.kbase.filters.KBAssertFilter

jade.semantics.kbase.filters.std.HornClauseFilter

public class HornClauseFilter
extends KBAssertFilter

The HornClauseFilter makes it possible to process the assertion of Horn clauses (like in Prolog). Horn clauses are disjunction of exactly one positive literal (the "head") and one or more negative literals (the "body"). In other words, they are material implications, the right hand-side of which (i.e. its consequent) is a single positive literal (and not a disjunction). For example:

 (B ??myself (implies (and p1 p2 ... pn)
                      q))
 

Which is logically equivalent to:

 (B ??myself (or (not p1) (not p2) ... (not pn))
                 q)
 

The application of this filter consists in installing a proper query filter for each asserted Horn clause. The installed query filter simply replaces queries on the head of the asserted Horn clause (i.e. the only positive literal of the clause) with queries on the conjunction of its body literals (i.e. the negative literals of the clause).

The HornClauseFilter is automatically loaded by the DefaultFilterKBaseLoader, so that default semantics agents benefit from it.

Since:

JSA 2

Author:

Thierry Martinez - France Telecom, Vincent Louis - France Telecom

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
(package private) class	HornClauseFilter.HornClauseQueryFilter Private class, which implements the query filter installed for each asserted Horn clause.

Field Summary

Fields

Modifier and Type	Field and Description
(package private) static int	count

Fields inherited from class jade.semantics.kbase.filters.KBFilter

myKBase

Constructor Summary

Constructors

Constructor and Description
HornClauseFilter()

Method Summary

Modifier and Type	Method and Description
Formula	apply(Formula formula) The apply(Formula) method applies on asserted Horn clauses.

Methods inherited from class jade.semantics.kbase.filters.KBAssertFilter

afterAssert, beforeAssert

Methods inherited from class jade.semantics.kbase.filters.KBFilter

getMyKBase, setMyKBase

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

count

static int count

Constructor Detail

HornClauseFilter

public HornClauseFilter()

Method Detail

apply

public Formula apply(Formula formula)

The apply(Formula) method applies on asserted Horn clauses. It consists in intalling dynamically a query filter that deals with queries on the head of the asserted Horn clause. Applies the filter before asserting the formula into the KBase. This method may modify the formula to assert by returning another formula. By default, it returns the same formula. The boolean mustApplyAfter is set to true.
Should be overridden.

Overrides:

apply in class KBAssertFilter

Parameters:

formula - the formula to assert

Returns:

the formula to assert into the KBase