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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 | |
---|---|
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 Detail |
---|
String getName()
String getURI()
int getArgLength()
boolean bodyCall(Node[] args, int length, RuleContext context)
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 enginescontext
- an execution context giving access to other relevant data
void headAction(Node[] args, int length, RuleContext context)
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 enginescontext
- an execution context giving access to other relevant databoolean isSafe()
boolean isMonotonic()
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