Package net.sf.tweety.lp.asp.syntax

Class DefaultNegation

  • All Implemented Interfaces:
    Formula, ComplexLogicalFormula, LogicStructure, SimpleLogicalFormula
    public class DefaultNegation
extends ASPBodyElement
    This class represents a default negated literal, i.e. "not a", where a is a classical atom or an aggregate atom.

    In answer set programming, the body of a rule is usually composed of a set of positive and negative literals, where this valuation refers to default negation or negation as failure. When implementing a rule, there are two opportunities:

    • implement the rule with two distinct lists, representing the sets of positive and negative literals
    • implement the rule with one set containing super literals, where a super literal can be positive or strictly negated, with or without default negation.

    This library takes the second approach, which allows more flexibility, but comes at the cost that malformed constructs like "not not a" are not intercepted by the library.

    Author:
    Tim Janus, Thomas Vengels, Anna Gessler

    • Constructor Detail

      • DefaultNegation

        public DefaultNegation​(ASPBodyElement at)
        Creates new default negation with the given literal.
        Parameters:
        at - a classical atom or an aggregate atom

    • Method Detail

      • toString

        public java.lang.String toString()
        Overrides:
        toString in class java.lang.Object

      • getLiterals

        public java.util.SortedSet<ASPLiteral> getLiterals()
        Description copied from class: ASPBodyElement
        Returns all literals in this element in form of a SortedSet. Literals are atoms or strict negations of atoms.
        Specified by:
        getLiterals in class ASPBodyElement
        Returns:
        all the literals used in the rule element

      • 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 class ASPElement
        Returns:
        the signature of the language of this formula.

      • isWellFormed

        public boolean isWellFormed()
        Description copied from interface: ComplexLogicalFormula
        Checks if this formula is well formed in the logical langauge. What well- formed means is highly language dependent and the documentation of implementing sub classes shall describe the well formed term for the language they model.
        Specified by:
        isWellFormed in interface ComplexLogicalFormula
        Overrides:
        isWellFormed in class ASPElement
        Returns:
        true if the formula is well-formed, false otherwise

      • isLiteral

        public boolean isLiteral()
        Returns:
        true if the formula represents a literal in the language or false otherwise

      • getTerms

        public java.util.Set<Term<?>> getTerms()
        Returns:
        a set containing all terms of this logical structure

      • getTerms

        public <C extends Term<?>> java.util.Set<C> getTerms​(java.lang.Class<C> cls)
        Description copied from interface: LogicStructure
        Processes the set containing all terms of type C. This method uses the equals method of the given Class and therefore does not add terms which are sub classes of type C to the set.
        Type Parameters:
        C - the type of terms
        Parameters:
        cls - The Class structure containing type information about the searched term
        Returns:
        A set containing all terms of type C of this logical structure

      • hashCode

        public int hashCode()
        Specified by:
        hashCode in interface SimpleLogicalFormula
        Overrides:
        hashCode in class java.lang.Object

      • equals

        public boolean equals​(java.lang.Object obj)
        Specified by:
        equals in interface SimpleLogicalFormula
        Overrides:
        equals in class java.lang.Object