net.sf.tweety.lp.asp.syntax

Class Rule

java.lang.Object

net.sf.tweety.logics.commons.syntax.ComplexLogicalFormulaAdapter

net.sf.tweety.lp.asp.syntax.DLPElementAdapter

net.sf.tweety.lp.asp.syntax.Rule

All Implemented Interfaces:

java.lang.Comparable<Rule>, Formula, Rule<DLPHead,DLPElement>, ComplexLogicalFormula, LogicStructure, SimpleLogicalFormula, DLPElement

public class Rule
extends DLPElementAdapter
implements java.lang.Comparable<Rule>, DLPElement, Rule<DLPHead,DLPElement>

This class models a rule for a disjunctive logic program. A rule is a collection of literals and more sophisticated rule elements like Aggregate or Arithmetic. It uses separate lists for the head and the body. It also implements the Comparable interface to allow for ordering in collections.

Author:

Tim Janus, Thomas Vengels

Field Summary

Fields

Modifier and Type	Field and Description
(package private) java.util.List<DLPElement>	body
(package private) DLPHead	head

Constructor Summary

Constructors

Constructor and Description
Rule() Default-Ctor: Creates an empty rule withouts any head literals or body elements
Rule(DLPHead head) Ctor: Create a rule with the given head.
Rule(DLPLiteral head) Ctor: Create a rule with the given head.
Rule(DLPLiteral head, DLPElement body)
Rule(DLPLiteral head, java.util.List<DLPElement> litsBody)
Rule(java.util.List<DLPLiteral> litsHead, java.util.List<DLPElement> litsBody)
Rule(Rule other) Copy-Ctor: Makes a deep copy of the given rule
Rule(java.lang.String ruleexpr)

Method Summary

Modifier and Type	Method and Description
void	addPremise(DLPElement premise)
void	addPremises(java.util.Collection<? extends DLPElement> premises)
Rule	clone() Creates a deep copy of this formula
int	compareTo(Rule arg0)
boolean	equals(java.lang.Object other)
java.util.Set<DLPAtom>	getAtoms() Processes the set of all atoms which appear in this formula
DLPHead	getConclusion() Returns the conclusion of this rule.
java.util.SortedSet<DLPLiteral>	getLiterals()
java.util.Set<DLPPredicate>	getPredicates() Processes the set of all predicates which appear in this formula
java.util.Collection<DLPElement>	getPremise() Returns the premise of this rule.
FolSignature	getSignature() Returns the signature of the language of this formula.
java.util.Set<Term<?>>	getTerms()
int	hashCode()
boolean	isConstraint()
boolean	isFact()
boolean	isSafe() Checks if the given rule is safe for use in a solver.
void	setConclusion(DLPHead conclusion)
void	setConclusion(DLPLiteral literal)
Rule	substitute(Term<?> v, Term<?> t) Substitutes all occurrences of term "v" in this formula by term "t" and returns the new formula.
java.lang.String	toString()

Methods inherited from class net.sf.tweety.lp.asp.syntax.DLPElementAdapter

getPredicateCls

Methods inherited from class net.sf.tweety.logics.commons.syntax.ComplexLogicalFormulaAdapter

containsTermsOfType, exchange, getTerms, isGround, isLiteral, isWellFormed, substitute

Methods inherited from class java.lang.Object

finalize, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface net.sf.tweety.logics.commons.syntax.interfaces.ComplexLogicalFormula

exchange, isGround, isWellFormed, substitute

Methods inherited from interface net.sf.tweety.logics.commons.syntax.interfaces.SimpleLogicalFormula

getPredicateCls, isLiteral

Methods inherited from interface net.sf.tweety.logics.commons.syntax.interfaces.LogicStructure

containsTermsOfType, getTerms

Field Detail

head

DLPHead head

body

java.util.List<DLPElement> body

Constructor Detail

Rule

public Rule()

Default-Ctor: Creates an empty rule withouts any head literals or body elements

Rule

public Rule(Rule other)

Copy-Ctor: Makes a deep copy of the given rule

Rule

public Rule(DLPHead head)

Ctor: Create a rule with the given head. Because there are no body elements, the created rule is a fact.

Parameters:

head - The head of the rule as ELPHead

Rule

public Rule(DLPLiteral head)

Ctor: Create a rule with the given head. Because there are no body elements, the created rule is a fact.

Parameters:

head - The head of the rule as ELPLiteral

Rule

public Rule(DLPLiteral head,
            DLPElement body)

Rule

public Rule(DLPLiteral head,
            java.util.List<DLPElement> litsBody)

Rule

public Rule(java.util.List<DLPLiteral> litsHead,
            java.util.List<DLPElement> litsBody)

Rule

public Rule(java.lang.String ruleexpr)

Method Detail

getLiterals

public java.util.SortedSet<DLPLiteral> getLiterals()

Specified by:

getLiterals in interface DLPElement

Returns:

all the literals used in the rule element

isFact

public boolean isFact()

Specified by:

isFact in interface Rule<DLPHead,DLPElement>

isConstraint

public boolean isConstraint()

Specified by:

isConstraint in interface Rule<DLPHead,DLPElement>

isSafe

public boolean isSafe()

Checks if the given rule is safe for use in a solver. The following excerpt from the DLV documentation explains when a rule is safe:

A variable X in an aggregate-free rule is safe if at least one of the following conditions is satisfied:
X occurs in a positive standard predicate in the body of the rule; X occurs in a true negated standard predicate in the body of the rule; X occurs in the last argument of an arithmetic predicate A and all other arguments of A are safe. (TODO: not supported yet). A rule is safe if all its variables are safe. However, cyclic dependencies are disallowed, e.g., :- #succ(X,Y), #succ(Y,X) is not safe.

Returns:

true if the rule is safe considering the above conditions, false otherwise.

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object

equals

public boolean equals(java.lang.Object other)

Specified by:

equals in interface SimpleLogicalFormula

Overrides:

equals in class java.lang.Object

hashCode

public int hashCode()

Specified by:

hashCode in interface SimpleLogicalFormula

Overrides:

hashCode in class java.lang.Object

compareTo

public int compareTo(Rule arg0)

Specified by:

compareTo in interface java.lang.Comparable<Rule>

clone

public Rule clone()

Description copied from interface: SimpleLogicalFormula

Creates a deep copy of this formula

Specified by:

clone in interface ComplexLogicalFormula

Specified by:

clone in interface SimpleLogicalFormula

Specified by:

clone in interface DLPElement

Specified by:

clone in class DLPElementAdapter

getSignature

public FolSignature getSignature()

Description copied from interface: Formula

Returns the signature of the language of this formula.

Specified by:

getSignature in interface Formula

Specified by:

getSignature in interface Rule<DLPHead,DLPElement>

Specified by:

getSignature in interface DLPElement

Returns:

the signature of the language of this formula.

getPremise

public java.util.Collection<DLPElement> getPremise()

Description copied from interface: Rule

Returns the premise of this rule.

Specified by:

getPremise in interface Rule<DLPHead,DLPElement>

Returns:

the premise of this rule.

getConclusion

public DLPHead getConclusion()

Description copied from interface: Rule

Returns the conclusion of this rule.

Specified by:

getConclusion in interface Rule<DLPHead,DLPElement>

Returns:

the conclusion of this rule.

substitute

public Rule substitute(Term<?> v,
                       Term<?> t)
                throws java.lang.IllegalArgumentException

Description copied from interface: ComplexLogicalFormula

Substitutes all occurrences of term "v" in this formula by term "t" and returns the new formula.

Specified by:

substitute in interface ComplexLogicalFormula

Specified by:

substitute in interface DLPElement

Parameters:

v - the term to be substituted.

t - the term to substitute.

Returns:

a formula where every occurrence of "v" is replaced by "t".

Throws:

java.lang.IllegalArgumentException - if "v" and "t" are of different sorts

getAtoms

public java.util.Set<DLPAtom> getAtoms()

Description copied from interface: SimpleLogicalFormula

Processes the set of all atoms which appear in this formula

Specified by:

getAtoms in interface SimpleLogicalFormula

Specified by:

getAtoms in interface DLPElement

Returns:

The set of all atoms

getPredicates

public java.util.Set<DLPPredicate> getPredicates()

Description copied from interface: SimpleLogicalFormula

Processes the set of all predicates which appear in this formula

Specified by:

getPredicates in interface SimpleLogicalFormula

Specified by:

getPredicates in interface DLPElement

Returns:

all predicates that appear in this formula

getTerms

public java.util.Set<Term<?>> getTerms()

Specified by:

getTerms in interface LogicStructure

Returns:

a set containing all terms of this logical structure

setConclusion

public void setConclusion(DLPHead conclusion)

Specified by:

setConclusion in interface Rule<DLPHead,DLPElement>

setConclusion

public void setConclusion(DLPLiteral literal)

addPremise

public void addPremise(DLPElement premise)

Specified by:

addPremise in interface Rule<DLPHead,DLPElement>

addPremises

public void addPremises(java.util.Collection<? extends DLPElement> premises)

Specified by:

addPremises in interface Rule<DLPHead,DLPElement>