001: /*
002: * Copyright (C) 1999-2004 <A href="http://www-ist.massey.ac.nz/JBDietrich" target="_top">Jens Dietrich</a>
003: *
004: * This library is free software; you can redistribute it and/or
005: * modify it under the terms of the GNU Lesser General Public
006: * License as published by the Free Software Foundation; either
007: * version 2 of the License, or (at your option) any later version.
008: *
009: * This library is distributed in the hope that it will be useful,
010: * but WITHOUT ANY WARRANTY; without even the implied warranty of
011: * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
012: * Lesser General Public License for more details.
013: *
014: * You should have received a copy of the GNU Lesser General Public
015: * License along with this library; if not, write to the Free Software
016: * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
017: */
018:
019: package org.mandarax.kernel;
020:
021: /**
022: * Clauses are clauses in the prolog sense, i.e. usually either rules or facts
023: * (= rules without body).
024: * @see org.mandarax.kernel.Fact
025: * @see org.mandarax.kernel.Rule
026: * @author <A href="http://www-ist.massey.ac.nz/JBDietrich" target="_top">Jens Dietrich</A>
027: * @version 3.4 <7 March 05>
028: * @since 1.0
029: * Prova re-integration
030: * @author <A HREF="mailto:a.kozlenkov@city.ac.uk">Alex Kozlenkov</A>
031: * @version 3.4 <7 March 05>
032: */
033: public interface Clause extends ClauseSet, SemanticsSupport {
034:
035: /**
036: * Apply a set of replacements to a clause. Returns a new clause!
037: * @see org.mandarax.kernel.Replacement
038: * @return the resulting clause
039: * @param r the set of replacements
040: */
041: public Clause apply(java.util.Collection r);
042:
043: /**
044: * Apply a single replacement to a clause.
045: * @see org.mandarax.kernel.Fact
046: * @return the resulting clause
047: * @param r the replacement
048: */
049: public Clause apply(Replacement r);
050:
051: /**
052: * Get the clause set containing the clause. This method is in particular useful for analyzing derivations,
053: * since derivations show only the clauses used, not the clause set generating this clauses (e.g., AutoFacts). On the other
054: * hand, knowledge bases contain often clause sets. So it could be hard to find the clause sets in the knowledge base
055: * that caused a certain result. For sme clauses such as facts, the container is just the fact itself.
056: * @return a clause set
057: */
058: ClauseSet getContainer();
059:
060: /**
061: * Get the negative literals.
062: * @return the list of negative literals
063: */
064: java.util.List getNegativeLiterals();
065:
066: /**
067: * Get the positive literals.
068: * @return the list of positive literals
069: */
070: java.util.List getPositiveLiterals();
071:
072: /**
073: * Whether the head contains variables
074: * @return boolean
075: */
076: boolean isBound();
077:
078: /**
079: * Indicates whether the clause is atomic, or is a real clause set containing other clauses.
080: * The main motivation for introducing this method are rules with prerequisites connected by OR.
081: * This rules are clauses, but they can also be seen as clause sets: A or B implies C is a clause set
082: * containing the two rules A implies C and B implies C.
083: * @return a boolean
084: */
085: boolean isAtomic();
086:
087: /**
088: * Indicates whether the clause is the empty clause.
089: * @return true if this is an empty clause, false otherwise
090: */
091: boolean isEmpty();
092:
093: /**
094: * Set a container.
095: * @param aContainerthe new container
096: */
097: void setContainer(ClauseSet aContainer);
098:
099: /**
100: * Indicates whether the clause is ground (= does not have variables).
101: * @return a boolean
102: */
103: boolean isGround();
104: }
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