net.sf.tweety.logics.rcl

Class RelationalBruteForceCReasoner

java.lang.Object

net.sf.tweety.commons.Reasoner

net.sf.tweety.logics.rcl.RelationalBruteForceCReasoner

public class RelationalBruteForceCReasoner
extends Reasoner

This class models a relational brute force c-reasoner for relational conditional logic. Reasoning is performed by computing a minimal c-representation for the given knowledge base.
A c-representation for a conditional knowledge base R={r1,...,rn} is a ranking function k such that k accepts every conditional in R (k |= R) and if there are numbers k0,k1+,k1-,...,kn+,kn- with
k(w)=k0 + \sum_{w verifies ri} ki+ + \sum_{w falsifies ri} kj- for every w. A c-representation is minimal if k0+...+kn- is minimal.
The c-representation is computed using a brute force approach.

See Gabriele Kern-Isberner. Conditionals in nonmonotonic reasoning and belief revision. Lecture Notes in Computer Science, Volume 2087. 2001.

See also [Kern-Isberner,Thimm, "A Ranking Semantics for Relational Defaults", in preparation].

Author:

Matthias Thimm

Field Summary

Fields

Modifier and Type	Field and Description
private RelationalRankingFunction	crepresentation The relational c-representation for the given knowledge base.
private java.util.Map<java.lang.Integer,RelationalConditional>	indexToConditional Maps the indices of the kappa vector to their corresponding conditionals.
private java.util.List<java.lang.Integer[]>	kappa The current vectors of kappa values.
private static org.slf4j.Logger	log Logger.
private int	numConditionals The number of conditionals in the given knowledge base.
private FolSignature	signature The signature used for building the c-representation.
private boolean	simple indicates whether the computed c-representation is simple.

Constructor Summary

Constructors

Constructor and Description
RelationalBruteForceCReasoner(BeliefBase beliefBase, FolSignature signature) Creates a new simple c-representation reasoner for the given knowledge base.
RelationalBruteForceCReasoner(BeliefBase beliefBase, FolSignature signature, boolean simple) Creates a new relational c-representation reasoner for the given knowledge base.

Method Summary

Modifier and Type	Method and Description
private RelationalRankingFunction	computeCRepresentation() Computes a minimal c-representation for this reasoner's knowledge base.
private RelationalRankingFunction	constructRankingFunction(java.lang.Integer[] kappa) Constructs a ranking function with the given kappa values [k1+,k1-,...,kn+,kn-], i.e.
RelationalRankingFunction	getCRepresentation() Returns the c-representation this reasoner bases on.
private java.lang.Integer[]	increment(java.lang.Integer[] kappa) This method increments the given array by one value.
private boolean	incrementStep(java.lang.Integer[] kappaRow) This method increments the given vector (which composes of exactly one "1" entry and zeros otherwise), e.g.
Answer	query(Formula query) This method determines the answer of the given query wrt.

Methods inherited from class net.sf.tweety.commons.Reasoner

getKnowledgeBase

Methods inherited from class java.lang.Object

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

Field Detail

log

private static org.slf4j.Logger log

Logger.

crepresentation

private RelationalRankingFunction crepresentation

The relational c-representation for the given knowledge base. Once this ranking function has been computed it is used for subsequent queries in order to avoid unnecessary computations.

kappa

private java.util.List<java.lang.Integer[]> kappa

The current vectors of kappa values.

numConditionals

private int numConditionals

The number of conditionals in the given knowledge base.

signature

private FolSignature signature

The signature used for building the c-representation.

indexToConditional

private java.util.Map<java.lang.Integer,RelationalConditional> indexToConditional

Maps the indices of the kappa vector to their corresponding conditionals.

simple

private boolean simple

indicates whether the computed c-representation is simple.

Constructor Detail

RelationalBruteForceCReasoner

public RelationalBruteForceCReasoner(BeliefBase beliefBase,
                                     FolSignature signature,
                                     boolean simple)

Creates a new relational c-representation reasoner for the given knowledge base.

Parameters:

beliefBase - a knowledge base.

signature - the signature used for building the c-representation.

simple - whether the computed c-representation is simple.

RelationalBruteForceCReasoner

public RelationalBruteForceCReasoner(BeliefBase beliefBase,
                                     FolSignature signature)

Creates a new simple c-representation reasoner for the given knowledge base.

Parameters:

beliefBase - a knowledge base.

signature - the signature used for building the c-representation.

Method Detail

getCRepresentation

public RelationalRankingFunction getCRepresentation()

Returns the c-representation this reasoner bases on.

Returns:

the c-representation this reasoner bases on.

query

public Answer query(Formula query)

Description copied from class: Reasoner

This method determines the answer of the given query wrt. to the given knowledge base.

Specified by:

query in class Reasoner

Parameters:

query - a query.

Returns:

the answer to the query.

computeCRepresentation

private RelationalRankingFunction computeCRepresentation()

Computes a minimal c-representation for this reasoner's knowledge base.

Returns:

a minimal c-representation for this reasoner's knowledge base.

constructRankingFunction

private RelationalRankingFunction constructRankingFunction(java.lang.Integer[] kappa)

Constructs a ranking function with the given kappa values [k1+,k1-,...,kn+,kn-], i.e. for every possible world w set
k(w)=k0 + \sum_{w verifies ri} ki+ + \sum_{w falsifies ri} kj-

Parameters:

kappa -

increment

private java.lang.Integer[] increment(java.lang.Integer[] kappa)

This method increments the given array by one value.

Parameters:

kappa - an array of integers.

Returns:

an array of integers.

incrementStep

private boolean incrementStep(java.lang.Integer[] kappaRow)

This method increments the given vector (which composes of exactly one "1" entry and zeros otherwise), e.g. [0,0,1,0] -> [0,0,0,1] and [0,0,0,1] -> [1,0,0,0]

Parameters:

kappaRow - a vector of zeros and one "1"

Returns:

"true" if there is an overflow, i.e. when [0,0,0,1] -> [1,0,0,0], otherwise "false".