Module org.apache.jena.core
Package org.apache.jena.reasoner.rulesys

Interface Builtin

All Known Implementing Classes:
AddOne, AssertDisjointPairs, BaseBuiltin, Bound, CountLiteralValues, Difference, Drop, Equal, GE, GreaterThan, Hide, IsBNode, IsDType, IsFunctor, IsLiteral, LE, LessThan, ListContains, ListEntry, ListEqual, ListLength, ListMapAsObject, ListMapAsSubject, ListNotContains, ListNotEqual, MakeInstance, MakeSkolem, MakeTemp, Max, Min, NotBNode, NotDType, NotEqual, NotFunctor, NotLiteral, NoValue, Now, Print, Product, Quotient, Regex, Remove, StrConcat, Sum, Table, TableAll, Unbound, UriConcat
public interface Builtin
Rules employ builtins to do all tests and actions other than simple triple matches and triple creation.

Builtins can be invoked in two contexts. In the head of forward rules they perform some action based on the variable bindings generated by the body and additional context (the graph being reasoned over, the set of triples bound by the body). In the body of rules they perform tests, and additional variable bindings.

The mapping from the rule definition (which uses functors to hold the parsed call) to the java implementation of the builtin is done via the BuiltinRegistry which can be user extended.

  • Method Summary

    Modifier and Type
    Method
    Description
    boolean
    bodyCall(Node[] args, int length, RuleContext context)
    This method is invoked when the builtin is called in a rule body.
    int
    getArgLength()
    Return the expected number of arguments for this functor or 0 if the number is flexible.
    String
    getName()
    Return a convenient name for this builtin, normally this will be the name of the functor that will be used to invoke it and will often be the final component of the URI.
    String
    getURI()
    Return the full URI which identifies this built in.
    void
    headAction(Node[] args, int length, RuleContext context)
    This method is invoked when the builtin is called in a rule head.
    boolean
    isMonotonic()
    Returns false if this builtin is non-monotonic.
    boolean
    isSafe()
    Returns false if this builtin has side effects when run in a body clause, other than the binding of environment variables.

  • Method Details

    • getName

      String getName()
      Return a convenient name for this builtin, normally this will be the name of the functor that will be used to invoke it and will often be the final component of the URI.

    • getURI

      String getURI()
      Return the full URI which identifies this built in.

    • getArgLength

      int getArgLength()
      Return the expected number of arguments for this functor or 0 if the number is flexible.

    • bodyCall

      boolean bodyCall(Node[] args, int length, RuleContext context)
      This method is invoked when the builtin is called in a rule body.
      Parameters:
      args - the array of argument values for the builtin, this is an array of Nodes, some of which may be Node_RuleVariables.
      length - the length of the argument list, may be less than the length of the args array for some rule engines
      context - an execution context giving access to other relevant data
      Returns:
      return true if the buildin predicate is deemed to have succeeded in the current environment

    • headAction

      void headAction(Node[] args, int length, RuleContext context)
      This method is invoked when the builtin is called in a rule head. Such a use is only valid in a forward rule.
      Parameters:
      args - the array of argument values for the builtin, this is an array of Nodes.
      length - the length of the argument list, may be less than the length of the args array for some rule engines
      context - an execution context giving access to other relevant data

    • isSafe

      boolean isSafe()
      Returns false if this builtin has side effects when run in a body clause, other than the binding of environment variables.

    • isMonotonic

      boolean isMonotonic()
      Returns false if this builtin is non-monotonic. This includes non-monotonic checks like noValue and non-monotonic actions like remove/drop. A non-monotonic call in a head is assumed to be an action and makes the overall rule and ruleset non-monotonic. Most JenaRules are monotonic deductive closure rules in which this should be false.