it.unibz.inf.ontop.iq.node.impl

Class EmptyNodeImpl

java.lang.Object

it.unibz.inf.ontop.iq.node.impl.QueryNodeImpl

it.unibz.inf.ontop.iq.node.impl.LeafIQTreeImpl

it.unibz.inf.ontop.iq.node.impl.EmptyNodeImpl

All Implemented Interfaces:

IQTree, LeafIQTree, EmptyNode, ExplicitVariableProjectionNode, QueryNode, Cloneable

public class EmptyNodeImpl
extends LeafIQTreeImpl
implements EmptyNode

Field Summary

Fields inherited from class it.unibz.inf.ontop.iq.node.impl.LeafIQTreeImpl

iqFactory

Method Summary

Modifier and Type	Method and Description
EmptyNode	acceptNodeTransformer(HomogeneousQueryNodeTransformer transformer) "Accept" method for the "Visitor" pattern.
IQTree	acceptTransformer(IQTreeVisitingTransformer transformer)
<T> T	acceptVisitor(IQVisitor<T> visitor)
void	acceptVisitor(QueryNodeVisitor visitor) "Accept" method for the "Visitor" pattern.
IQTree	applyDescendingSubstitutionWithoutOptimizing(ImmutableSubstitution<? extends VariableOrGroundTerm> descendingSubstitution) Applies the descending substitution WITHOUT applying any additional optimization.
IQTree	applyFreshRenaming(InjectiveVar2VarSubstitution freshRenamingSubstitution) Particular type of descending substitution: only renaming some variables by external ones.
EmptyNode	clone() See https://stackoverflow.com/questions/6837362/
com.google.common.collect.ImmutableSet<Variable>	getKnownVariables() Variables present in the tree
com.google.common.collect.ImmutableSet<Variable>	getLocallyDefinedVariables() Locally defined variables must not appear in the sub-tree
com.google.common.collect.ImmutableSet<Variable>	getLocallyRequiredVariables() Set of variables that this node, INDEPENDENTLY OF THE REQUIREMENTS OF ITS ANCESTORS, requires to be defined in the sub-tree.
com.google.common.collect.ImmutableSet<Variable>	getLocalVariables() Set of variables MENTIONED in the node, INDEPENDENTLY of its sub-tree.
com.google.common.collect.ImmutableSet<Variable>	getRequiredVariables(IntermediateQuery query) Set of variables which, individually, must be provided by at least one child, INDEPENDENTLY OF THE REQUIREMENTS OF THIS NODE'S ANCESTORS.
VariableNullability	getVariableNullability()
com.google.common.collect.ImmutableSet<Variable>	getVariables() Variables projected by the tree
com.google.common.collect.ImmutableSet<com.google.common.collect.ImmutableSet<Variable>>	inferUniqueConstraints() NOT guaranteed to return all the unique constraints (MAY BE INCOMPLETE) Set of sets of determinants
boolean	isDeclaredAsEmpty() Returns true if corresponds to a EmptyNode
boolean	isDistinct() Returns true if it guarantees that all its results will be distinct
boolean	isEquivalentTo(QueryNode queryNode) Is syntactically equivalent
boolean	isSyntacticallyEquivalentTo(QueryNode node) TODO: explain
boolean	isVariableNullable(IntermediateQuery query, Variable variable) Returns true if it cannot guarantee the projected variable to be non-null Throws an IllegalArgumentException if the variable is not projected by the node
String	toString()
void	validate()

Methods inherited from class it.unibz.inf.ontop.iq.node.impl.LeafIQTreeImpl

applyDescendingSubstitution, getChildren, getPossibleVariableDefinitions, getRootNode, isConstructed, isEquivalentTo, liftIncompatibleDefinitions, normalizeForOptimization, propagateDownConstraint, removeDistincts, replaceSubTree

Methods inherited from class java.lang.Object

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

Methods inherited from interface it.unibz.inf.ontop.iq.LeafIQTree

getRootNode

Methods inherited from interface it.unibz.inf.ontop.iq.IQTree

applyDescendingSubstitution, getChildren, getPossibleVariableDefinitions, isConstructed, isEquivalentTo, isLeaf, liftIncompatibleDefinitions, normalizeForOptimization, propagateDownConstraint, removeDistincts, replaceSubTree

Method Detail

acceptVisitor

public void acceptVisitor(QueryNodeVisitor visitor)

Description copied from interface: QueryNode

"Accept" method for the "Visitor" pattern. To be implemented by leaf classes.

Specified by:

acceptVisitor in interface QueryNode

acceptNodeTransformer

public EmptyNode acceptNodeTransformer(HomogeneousQueryNodeTransformer transformer)
                                throws QueryNodeTransformationException

Description copied from interface: QueryNode

"Accept" method for the "Visitor" pattern. To be implemented by leaf classes. If the transformation cannot be done, throw a QueryNodeTransformationException

Specified by:

acceptNodeTransformer in interface LeafIQTree

Specified by:

acceptNodeTransformer in interface EmptyNode

Specified by:

acceptNodeTransformer in interface QueryNode

Throws:

QueryNodeTransformationException

getLocalVariables

public com.google.common.collect.ImmutableSet<Variable> getLocalVariables()

Description copied from interface: QueryNode

Set of variables MENTIONED in the node, INDEPENDENTLY of its sub-tree. See ImmutableQuery.getVariables(QueryNode node) for getting all the variables returned by the QueryNode.

Specified by:

getLocalVariables in interface QueryNode

isVariableNullable

public boolean isVariableNullable(IntermediateQuery query,
                                  Variable variable)

Description copied from interface: QueryNode

Returns true if it cannot guarantee the projected variable to be non-null Throws an IllegalArgumentException if the variable is not projected by the node

Specified by:

isVariableNullable in interface QueryNode

isSyntacticallyEquivalentTo

public boolean isSyntacticallyEquivalentTo(QueryNode node)

Description copied from interface: QueryNode

TODO: explain

Specified by:

isSyntacticallyEquivalentTo in interface QueryNode

clone

public EmptyNode clone()

Description copied from class: QueryNodeImpl

See https://stackoverflow.com/questions/6837362/

Specified by:

clone in interface EmptyNode

Specified by:

clone in interface QueryNode

Overrides:

clone in class QueryNodeImpl

toString

public String toString()

Overrides:

toString in class Object

getVariables

public com.google.common.collect.ImmutableSet<Variable> getVariables()

Description copied from interface: IQTree

Variables projected by the tree

Specified by:

getVariables in interface IQTree

Specified by:

getVariables in interface ExplicitVariableProjectionNode

acceptTransformer

public IQTree acceptTransformer(IQTreeVisitingTransformer transformer)

Specified by:

acceptTransformer in interface IQTree

acceptVisitor

public <T> T acceptVisitor(IQVisitor<T> visitor)

Specified by:

acceptVisitor in interface IQTree

applyFreshRenaming

public IQTree applyFreshRenaming(InjectiveVar2VarSubstitution freshRenamingSubstitution)

Description copied from interface: IQTree

Particular type of descending substitution: only renaming some variables by external ones. Isolated from regular descending substitutions as it preserves the properties of the tree (e.g. it remains normalized if it was already)

Specified by:

applyFreshRenaming in interface IQTree

applyDescendingSubstitutionWithoutOptimizing

public IQTree applyDescendingSubstitutionWithoutOptimizing(ImmutableSubstitution<? extends VariableOrGroundTerm> descendingSubstitution)

Description copied from interface: IQTree

Applies the descending substitution WITHOUT applying any additional optimization. Designed to be called AFTER the "structural/semantic optimization" phase.

Specified by:

applyDescendingSubstitutionWithoutOptimizing in interface IQTree

getKnownVariables

public com.google.common.collect.ImmutableSet<Variable> getKnownVariables()

Description copied from interface: IQTree

Variables present in the tree

Specified by:

getKnownVariables in interface IQTree

isDistinct

public boolean isDistinct()

Description copied from interface: IQTree

Returns true if it guarantees that all its results will be distinct

Specified by:

isDistinct in interface IQTree

isDeclaredAsEmpty

public boolean isDeclaredAsEmpty()

Description copied from interface: IQTree

Returns true if corresponds to a EmptyNode

Specified by:

isDeclaredAsEmpty in interface IQTree

getVariableNullability

public VariableNullability getVariableNullability()

Specified by:

getVariableNullability in interface IQTree

validate

public void validate()
              throws InvalidIntermediateQueryException

Specified by:

validate in interface IQTree

Throws:

InvalidIntermediateQueryException

inferUniqueConstraints

public com.google.common.collect.ImmutableSet<com.google.common.collect.ImmutableSet<Variable>> inferUniqueConstraints()

Description copied from interface: IQTree

NOT guaranteed to return all the unique constraints (MAY BE INCOMPLETE) Set of sets of determinants

Specified by:

inferUniqueConstraints in interface IQTree

getLocallyRequiredVariables

public com.google.common.collect.ImmutableSet<Variable> getLocallyRequiredVariables()

Description copied from interface: QueryNode

Set of variables that this node, INDEPENDENTLY OF THE REQUIREMENTS OF ITS ANCESTORS, requires to be defined in the sub-tree. Said differently, additional variable requirements may come from its ancestors.

Specified by:

getLocallyRequiredVariables in interface QueryNode

getRequiredVariables

public com.google.common.collect.ImmutableSet<Variable> getRequiredVariables(IntermediateQuery query)

Description copied from interface: QueryNode

Set of variables which, individually, must be provided by at least one child, INDEPENDENTLY OF THE REQUIREMENTS OF THIS NODE'S ANCESTORS. This may extend locally required variables. For instance, for a join node, this includes variables used in implicit joining conditions

Specified by:

getRequiredVariables in interface QueryNode

getLocallyDefinedVariables

public com.google.common.collect.ImmutableSet<Variable> getLocallyDefinedVariables()

Description copied from interface: QueryNode

Locally defined variables must not appear in the sub-tree

Specified by:

getLocallyDefinedVariables in interface QueryNode

isEquivalentTo

public boolean isEquivalentTo(QueryNode queryNode)

Description copied from interface: QueryNode

Is syntactically equivalent

Specified by:

isEquivalentTo in interface QueryNode