it.unibz.inf.ontop.model.term.impl

Class DBConstantImpl

java.lang.Object

it.unibz.inf.ontop.model.term.impl.AbstractNonFunctionalTerm

it.unibz.inf.ontop.model.term.impl.AbstractNonNullConstant

it.unibz.inf.ontop.model.term.impl.DBConstantImpl

All Implemented Interfaces:

Constant, DBConstant, GroundTerm, ImmutableTerm, NonFunctionalTerm, NonNullConstant, NonVariableTerm, Term, VariableOrGroundTerm, Serializable

public class DBConstantImpl
extends AbstractNonNullConstant
implements DBConstant

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
DBConstantImpl(String value, DBTermType termType)

Method Summary

Modifier and Type	Method and Description
Term	clone()
boolean	equals(Object other) This method directly refers to the notion of strict-equality.
IncrementalEvaluation	evaluateStrictEq(ImmutableTerm otherTerm, VariableNullability variableNullability)
DBTermType	getType()
String	getValue()
Stream<Variable>	getVariableStream()
int	hashCode()
boolean	isGround()
String	toString() TODO: should we print differently?

Methods inherited from class it.unibz.inf.ontop.model.term.impl.AbstractNonNullConstant

evaluateIsNotNull, isNullable

Methods inherited from class it.unibz.inf.ontop.model.term.impl.AbstractNonFunctionalTerm

simplify, simplify

Methods inherited from class java.lang.Object

finalize, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface it.unibz.inf.ontop.model.term.NonNullConstant

getOptionalType, inferType, isNull

Methods inherited from interface it.unibz.inf.ontop.model.term.Constant

isDeterministic

Methods inherited from interface it.unibz.inf.ontop.model.term.ImmutableTerm

evaluateIsNotNull, isNullable, simplify, simplify

Constructor Detail

DBConstantImpl

public DBConstantImpl(String value,
                      DBTermType termType)

Method Detail

getType

public DBTermType getType()

Specified by:

getType in interface DBConstant

Specified by:

getType in interface NonNullConstant

getValue

public String getValue()

Specified by:

getValue in interface Constant

isGround

public boolean isGround()

Specified by:

isGround in interface ImmutableTerm

getVariableStream

public Stream<Variable> getVariableStream()

Specified by:

getVariableStream in interface ImmutableTerm

toString

public String toString()

TODO: should we print differently?

Overrides:

toString in class Object

hashCode

public int hashCode()

Overrides:

hashCode in class Object

equals

public boolean equals(Object other)

This method directly refers to the notion of strict-equality. Is under 2VL and treats the NULLs of strict-equalities as false. For DBConstants, term types are NOT CONSIDERED for this test. Only the lexical string matters. This tolerance initially comes from the fact that DBs like PostgreSQL offer almost-identical datatypes such as SERIAL and INT4 over which one would like to join and over which foreign keys may hold. For the sake of simplicity, Ontop treats these types as equivalent in strict-equality, which enables FK-based optimization to be applied. Observes that the tiny technical difference between SERIAL and INT4 is irrelevant for the scope of Ontop. Also observe that users CANNOT specify directly a strict-equality over DB terms. Equalities in the user-provided mapping are first treated as "not yet typed" and are later transformed based on their types. And for what regards SPARQL, it deals with RDF terms, not DB terms. This means that strict-equalities between DB terms are produced internally, in situations where Ontop should be able to use them in a meaningful manner.

Overrides:

equals in class Object

evaluateStrictEq

public IncrementalEvaluation evaluateStrictEq(ImmutableTerm otherTerm,
                                              VariableNullability variableNullability)

Specified by:

evaluateStrictEq in interface ImmutableTerm

clone

public Term clone()

Specified by:

clone in interface Term

Overrides:

clone in class Object