org.aksw.sparqlify.core.cast

Class EffectiveViewGenerator

java.lang.Object

org.aksw.sparqlify.core.cast.EffectiveViewGenerator

public class EffectiveViewGenerator
extends Object

Create { ?s rdfs:label ?n . ?s ex:age ?a . } With ?s = ?n = plainLiteral(?name) ?a = typedLiteral(?age, xsd:int) From Student --> SELECT ... WHERE id | name | age 1 | Foo | 20 2 | Bar | null 3 | Baz | 40 We can't just do "WHERE NOT NULL" ... A simple refactoring would be Create { ?s rdfs:label ?n . } With ?s = ?n = plainLiteral(?name) From [[SELECT * FROM Student WHERE name IS NOT NULL]] --> if we joined that, we could do JOIN(FILTER(r, a), FILTER(s, b)) -> FILTER(JOIN(a, b), rxs) Take care to rename column references as needed. Create { ?s rdfs:label ?n . } With ?s = ?n = plainLiteral(?name) From [[SELECT * FROM Student WHERE name IS NOT NULL]] Note: coalesce wouldn't work: The arguments could be NULL so the condidition would be COALESCE(a, b, c) IS NOT NULL... this could be further transformed to a IS NOT NULL OR b IS NOT NULL OR c IS NOT NULL

Author:

raven TODO Combine view ViewRefactor class

Constructor Summary

Constructors

Constructor and Description
EffectiveViewGenerator()

Method Summary

Methods

Modifier and Type	Method and Description
List<ViewDefinition>	addNullConstraints(ViewDefinition viewDef)
static SqlOp	createMinimalSchema(SqlOp sqlOp, VarDefinition varDef)
static List<ViewDefinition>	createQuadMaps(ViewDefinition viewDef)
static boolean	isNullable(com.hp.hpl.jena.sparql.expr.Expr expr, Schema schema) FIXME Improve this method A simple nullable check for expressions.
List<ViewDefinition>	transform(ViewDefinition viewDef) Adds "columnName" IS NOT NULL constraints to the view definitions according to the schema.
List<ViewDefinition>	transformDummy(ViewDefinition viewDef)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

EffectiveViewGenerator

public EffectiveViewGenerator()

Method Detail

isNullable

public static boolean isNullable(com.hp.hpl.jena.sparql.expr.Expr expr,
                 Schema schema)

FIXME Improve this method A simple nullable check for expressions. It returns true if any of the referenced columns is nullable

Parameters:

expr -

schema -

Returns:

transformDummy

public List<ViewDefinition> transformDummy(ViewDefinition viewDef)

createQuadMaps

public static List<ViewDefinition> createQuadMaps(ViewDefinition viewDef)

createMinimalSchema

public static SqlOp createMinimalSchema(SqlOp sqlOp,
                        VarDefinition varDef)

transform

public List<ViewDefinition> transform(ViewDefinition viewDef)

Adds "columnName" IS NOT NULL constraints to the view definitions according to the schema. Note: Optimization of expressions such as (?x IS NOT NULL) AND (?x = 1) -> (?x = 1) have to happen at a later stage.

Parameters:

viewDef -

Returns:

addNullConstraints

public List<ViewDefinition> addNullConstraints(ViewDefinition viewDef)