org.aksw.sparqlify.core.datatypes

Interface SparqlFunction

All Known Implementing Classes:

SparqlFunctionImpl

public interface SparqlFunction

Method Summary

Methods

Modifier and Type	Method and Description
SqlExprEvaluator	getEvaluator() An object that may evaluate the result of a SPARQL function based on its (raw) arguments (Expr objects) Used for reusing Jena's Expr.eval(...) methods.
String	getName()
MethodSignature<TypeToken>	getSignature() Sparql Functions can have a signature: object -> http://sparqlify.org/vocab/type/Object (anything) plainLiteral -> http://sparqlify.org/vocab/type/PlainLitera Note this signature refers to RDF types!!! - NOT SQL ONES! nonRdfTermObject -> http://sparqlify.org/vocab/type/NrtObject (excludes URIs, blanknodes and literals)
Collection<XMethod>	getSqlMethods() Deprecated.
ExprSubstitutor	getSubstitutor() A substitutor may yield a new, rewritten, expression based on the given argument types.
SqlMethodCandidate	lookup(List<TypeToken> argTypes) Deprecated.

Method Detail

getName

String getName()

Returns:

The name of the function

getSignature

MethodSignature<TypeToken> getSignature()

Sparql Functions can have a signature: object -> http://sparqlify.org/vocab/type/Object (anything) plainLiteral -> http://sparqlify.org/vocab/type/PlainLitera Note this signature refers to RDF types!!! - NOT SQL ONES! nonRdfTermObject -> http://sparqlify.org/vocab/type/NrtObject (excludes URIs, blanknodes and literals)

Returns:

getEvaluator

SqlExprEvaluator getEvaluator()

An object that may evaluate the result of a SPARQL function based on its (raw) arguments (Expr objects) Used for reusing Jena's Expr.eval(...) methods.

Returns:

An object that can evaluate the function for given arguments. NULL if no evaluator exists.

getSubstitutor

ExprSubstitutor getSubstitutor()

A substitutor may yield a new, rewritten, expression based on the given argument types. Used to specify transformation to SQL functions. E.g. ogc:intersects(ogc:geometry a, ogc:geometry b, dist) -> plainLiteral(ST_INTERSECTS(a, b 1000 * dist)) . If both arguments to ogc:intersects are constants, we could compute the result on the Java level (provided we registered such evaluator). . We could also register a transformation that eventually uses ST_INTERSECTS to archieve this goal. . ISSUE What is the role of the signature then? Essentially I want to be able to state, that some (SPARQL?) function is capable of converting between e.g. integer and double. This could be done with typeSystem.registerCoercion("src", "dst", new CoercionSparqlFunction(typeSystem, "myFunc")); If a function invocation (e.g. using E_Function or E_Call) cannot be evaluated, nor rewritten, it is assumed that the arguments are invalid, and a type error is raised.

Returns:

getSqlMethods

@Deprecated
Collection<XMethod> getSqlMethods()

Deprecated.

Returns:

The set of SQL methods registered for this Sparql Function. Should be consistent with an evaluator.

lookup

@Deprecated
SqlMethodCandidate lookup(List<TypeToken> argTypes)

Deprecated.

Parameters:

argTypes -

Returns:

The SQL function registered with this SPARQL function that matches the given arguments best.