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A Java API for Meta-CSP based reasoning
/*******************************************************************************
* Copyright (c) 2010-2013 Federico Pecora
*
* Permission is hereby granted, free of charge, to any person obtaining
* a copy of this software and associated documentation files (the
* "Software"), to deal in the Software without restriction, including
* without limitation the rights to use, copy, modify, merge, publish,
* distribute, sublicense, and/or sell copies of the Software, and to
* permit persons to whom the Software is furnished to do so, subject to
* the following conditions:
*
* The above copyright notice and this permission notice shall be
* included in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
* LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
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* WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
******************************************************************************/
package org.metacsp.framework.meta;
import java.util.Arrays;
import java.util.logging.Logger;
import org.metacsp.framework.Constraint;
import org.metacsp.framework.ConstraintNetwork;
import org.metacsp.framework.ConstraintSolver;
import org.metacsp.framework.ValueOrderingH;
import org.metacsp.framework.VariableOrderingH;
import org.metacsp.utility.logging.MetaCSPLogging;
/**
* A {@link MetaConstraint} is a generalization of the concept of constraint in classical CSPs. Like variables in a metaCSP,
* constraints are often implicit - e.g., a resource in scheduling, whose principal feature is a capacity; or an operator in planning,
* whose principal features are expressed as preconditions and effects. All {@link MetaConstraint}s have in common a number of
* features:
*
* - They represent a set of requirements which must be upheld in the particular application domain (e.g., no over-consumption of
* resources in scheduling).
* - They subsume one or more concrete constraints that are relevant for the ground solvers - e.g., n-ary
* nogoods in resource scheduling.
* - They can be used to synthesize values for the {@link MetaVariable}s in the meta-CSP - e.g., ordering constraints
* for the activities in a scheduling problem.
*
* Often it is also the case that value and variable ordering heuristics for meta-CSP search are related to the meta-CSP's {@link MetaConstraint}s.
* For instance, in scheduling, a variable ordering heuristic may use the capacity of a resource to assess how critical a particular
* conflict set is.
*
* @author Federico Pecora
*
*/
public abstract class MetaConstraint extends Constraint {
private static final long serialVersionUID = 3972541057627681253L;
protected VariableOrderingH varOH;
protected ValueOrderingH valOH;
protected MetaConstraintSolver metaCS = null;
protected boolean independentMC = false;
/**
* Creates a {@link MetaConstraint} with given variable and value ordering heuristics (one or both of these can be null).
* This constructor must be called by the implementing class.
* @param varOH The variable ordering heuristic to be used by the meta-CSP search when dealing with this {@link MetaConstraint}.
* @param valOH The value ordering heuristic to be used by the meta-CSP search when dealing with this {@link MetaConstraint}.
*/
public MetaConstraint(VariableOrderingH varOH, ValueOrderingH valOH) {
this.varOH = varOH;
this.valOH = valOH;
}
/**
* Set the {@link MetaConstraintSolver} of this {@link MetaConstraint}.
* @param metaCS The {@link MetaConstraintSolver} of this {@link MetaConstraint}.
*/
public void setMetaSolver(MetaConstraintSolver metaCS) {
this.metaCS = metaCS;
logger.finest("Set MetaConstraintSolver to " + metaCS.getDescription());
}
/**
* Get one {@link MetaVariable} according to this {@link MetaConstraint}. This returns the
* highest-priority {@link MetaVariable} according to this {@link MetaConstraint}'s variable ordering heuristic.
* @return A {@link MetaVariable} according to this {@link MetaConstraint}.
*/
public ConstraintNetwork getMetaVariable() {
ConstraintNetwork[] vars = this.getMetaVariables();
if (vars != null && vars.length > 0) {
if (varOH != null) {
varOH.collectData(vars);
Arrays.sort(vars, varOH);
}
return vars[0];
}
return null;
}
/**
* Get all {@link MetaVariable}s according to this {@link MetaConstraint}. This method must be implemented by the
* designer of the implementing {@link MetaConstraint} class.
* @return All {@link MetaVariable}s according to this {@link MetaConstraint}.
*/
public abstract ConstraintNetwork[] getMetaVariables();
//public abstract boolean metaPropagation(ConstraintNetwork metaValue);
/**
* Get one meta value for a given {@link MetaVariable}. Note that this calls
* the getMetaValues method (which must be implemented in the specific
* {@link MetaConstraint}) and returns the value with highest score as determined
* by this {@link MetaConstraint}'s {@link ValueOrderingH}.
* @param metaVariable The {@link MetaVariable} for which we seek a meta value.
* @return The best meta value for the given {@link MetaVariable}.
*/
public ConstraintNetwork getMetaValue(MetaVariable metaVariable) {
ConstraintNetwork[] vals = this.getMetaValues(metaVariable);
if (valOH != null) Arrays.sort(vals, valOH);
return vals[0];
}
/**
* Get all meta values for a given {@link MetaVariable}. This method must be
* implemented in the specific {@link MetaConstraint}.
* @param metaVariable The {@link MetaVariable} for which we seek meta values.
* @return All meta values for the given {@link MetaVariable}.
*/
public abstract ConstraintNetwork[] getMetaValues(MetaVariable metaVariable);
/**
* Method to mark a {@link MetaVariable} as solved. This method is called by the
* {@link MetaConstraintSolver} and must be implemented by the developer of the
* {@link MetaConstraint}.
* @param metaVariable The {@link MetaVariable} that is to be considered solved by
* the given meta value.
* @param metaValue The solving meta value.
*/
public abstract void markResolvedSub(MetaVariable metaVariable, ConstraintNetwork metaValue);
/**
* Method to draw the metaCSP's constraint network according to the rationale of
* this {@link MetaConstraint} (e.g., for a resource, this could be the resource usage profile
* as it is determined by the given constraint network). This method must be implemented by the
* developer of the {@link MetaConstraint}.
* @param network The constraint network to draw.
*/
public abstract void draw(final ConstraintNetwork network);
@Override
public String getDescription() {
String ret = "[";
ret += this.getClass().getSimpleName() + " varOH: " + (this.varOH != null ? this.varOH.getClass().getSimpleName() : "null") + " valOH: " + (this.valOH != null ? this.varOH.getClass().getSimpleName() : "null") + "]";
return ret;
}
/**
* Method to get the Variable Ordering heuristic used by this {@link MetaConstraint}.
* @return the Variable Ordering heuristic used by this {@link MetaConstraint}.
*/
public VariableOrderingH getVarOH() {
return varOH;
}
/**
* Method to set the Variable Ordering heuristic of this {@link MetaConstraint}.
* @param varOH the Variable Ordering heuristic of this {@link MetaConstraint}
*/
public void setVarOH(VariableOrderingH varOH) {
this.varOH = varOH;
}
/**
* Method to get the Value Ordering heuristic used by this {@link MetaConstraint}.
* @return the Value Ordering heuristic used by this {@link MetaConstraint}.
*/
public ValueOrderingH getValOH() {
return valOH;
}
/**
* Method to set the Value Ordering heuristic of this {@link MetaConstraint}.
* @param valOH the Value Ordering heuristic of this {@link MetaConstraint}
*/
public void setValOH(ValueOrderingH valOH) {
this.valOH = valOH;
}
/**
* Provides the definition of how to get the/a groundSolver for this {@link MetaConstraint}.
* @return The/a groundSolver for this {@link MetaConstraint}.
*/
public abstract ConstraintSolver getGroundSolver();
}