org.semanticweb.elk.reasoner.saturation
Class ContextImpl

java.lang.Object
  org.semanticweb.elk.reasoner.saturation.ContextImpl

All Implemented Interfaces:

Context

public class ContextImpl
extends Object
implements Context

Context implementation that is used for EL reasoning. It provides data structures for storing and retrieving various types of derived expressions, including computed subsumptions between class expressions.

Author:

Markus Kroetzsch, Frantisek Simancik, "Yevgeny Kazakov"

Field Summary

protected boolean	isInconsistent true if owl:Nothing is stored in subsumers_
protected boolean	isSaturated true if all derived Subsumer of root_ have been computed.

Constructor Summary

ContextImpl(IndexedClassExpression root)
Construct a new Context for the given root IndexedClassExpression.

Method Summary

boolean	addBackwardLink(BackwardLink link) Adds the given BackwardLink to this Context.
boolean	addDisjointnessAxiom(IndexedDisjointnessAxiom disjointnessAxiom) Adds one instance of IndexedDisjointnessAxiom to this Context.
boolean	addSubsumer(IndexedClassExpression expression) Adds the given IndexedClassExpression to the subsumers of the root IndexedClassExpression of this Context.
boolean	addToDo(Conclusion conclusion) Adds the given Conclusion to be processed within this Context.
boolean	containsBackwardLink(BackwardLink link)
boolean	containsDisjointnessAxiom(IndexedDisjointnessAxiom axiom)
boolean	containsSubsumer(IndexedClassExpression expression) Tests whether the given IndexedClassExpression is a subsumer of the root IndexedClassExpression of this Context.
AbstractChain<ModifiableLinkRule<BackwardLink>>	getBackwardLinkRuleChain()
ModifiableLinkRule<BackwardLink>	getBackwardLinkRuleHead()
Multimap<IndexedPropertyChain,Context>	getBackwardLinksByObjectProperty()
IndexedClassExpression	getRoot()
Set<IndexedClassExpression>	getSubsumers()
boolean	inconsistencyDisjointnessAxiom(IndexedDisjointnessAxiom axiom)
boolean	isEmpty()
boolean	isInconsistent()
boolean	isSaturated()
boolean	removeBackwardLink(BackwardLink link)
boolean	removeDisjointnessAxiom(IndexedDisjointnessAxiom axiom) Removes one instance of the given IndexedDisjointnessAxiom from this Context.
void	removeLinks() removes links to the next and previous contexts, effectively removing this Context from the chain of contexts
boolean	removeSubsumer(IndexedClassExpression expression) Removes the given IndexedClassExpression from the subsumers of the root IndexedClassExpression of this Context.
boolean	setInconsistent(boolean inconsistent) Sets the inconsistency of this Context to the given value.
boolean	setSaturated(boolean saturated) Marks this Context as saturated.
Conclusion	takeToDo() Removes and returns one of the unprocessed Conclusions of this context.
String	toString()

Methods inherited from class java.lang.Object

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

Field Detail

isSaturated

protected volatile boolean isSaturated

true if all derived Subsumer of root_ have been computed.

isInconsistent

protected volatile boolean isInconsistent

true if owl:Nothing is stored in subsumers_

Constructor Detail

ContextImpl

public ContextImpl(IndexedClassExpression root)

Construct a new Context for the given root IndexedClassExpression. Initially, the context is not active.

Parameters:

root -

Method Detail

getRoot

public IndexedClassExpression getRoot()

Specified by:

getRoot in interface Context

Returns:

the IndexedClassExpression for which this Context is assigned. This may never been null.

removeLinks

public void removeLinks()

Description copied from interface: Context

removes links to the next and previous contexts, effectively removing this Context from the chain of contexts

Specified by:

removeLinks in interface Context

getSubsumers

public Set<IndexedClassExpression> getSubsumers()

Specified by:

getSubsumers in interface Context

Returns:

the object representing all derived (implied) IndexedClassExpressions that subsume the root IndexedClassExpression

addSubsumer

public boolean addSubsumer(IndexedClassExpression expression)

Description copied from interface: Context

Adds the given IndexedClassExpression to the subsumers of the root IndexedClassExpression of this Context.

Specified by:

addSubsumer in interface Context

Parameters:

expression - the IndexedClassExpression to be added as a susbumer of the root IndexedClassExpression of this Context.

Returns:

true if the set of subsumers of this Context has changed as the result of calling this method, i.e., the input IndexedClassExpression was not a subsumer before. This method is not thread safe.

containsSubsumer

public boolean containsSubsumer(IndexedClassExpression expression)

Description copied from interface: Context

Tests whether the given IndexedClassExpression is a subsumer of the root IndexedClassExpression of this Context.

Specified by:

containsSubsumer in interface Context

Parameters:

expression - the IndexedClassExpression to be tested for this Context

Returns:

true if the given IndexedClassExpression is a subsumer of the root in this Context. This method is not thread safe.

removeSubsumer

public boolean removeSubsumer(IndexedClassExpression expression)

Description copied from interface: Context

Removes the given IndexedClassExpression from the subsumers of the root IndexedClassExpression of this Context.

Specified by:

removeSubsumer in interface Context

Parameters:

expression - the IndexedClassExpression to be removed from the subsumers of the root in this Context

Returns:

true if the set of subsumers of this Context has changed as the result of calling this method, i.e., the input IndexedClassExpression was a subsumer before. This method is not thread safe.

isInconsistent

public boolean isInconsistent()

Specified by:

isInconsistent in interface Context

Returns:

true if a contradiction has not been derived for the root IndexedClassExpression

setInconsistent

public boolean setInconsistent(boolean inconsistent)

Description copied from interface: Context

Sets the inconsistency of this Context to the given value.

Specified by:

setInconsistent in interface Context

Returns:

the previous inconsistency value

getBackwardLinksByObjectProperty

public Multimap<IndexedPropertyChain,Context> getBackwardLinksByObjectProperty()

Specified by:

getBackwardLinksByObjectProperty in interface Context

Returns:

the Contexts from which there exists an (implied) "existential relation" with this Context indexed by the IndexedPropertyChain of this relation. For example, if the input ontology contains an axiom SubClassOf(:A ObjectSomeValuesFrom(:r :B) then an existential link between the context with root :A and the context with root :B with property :r will be created. For technical reasons, this link is stored in the context for :B, as a "backward link" <:r, :A> indexed by :r in the Multimap returned by this method. The returned Multimap is not thread safe and should be accessed from at most one thread at a time. This is never null.

containsBackwardLink

public boolean containsBackwardLink(BackwardLink link)

Specified by:

containsBackwardLink in interface Context

addDisjointnessAxiom

public boolean addDisjointnessAxiom(IndexedDisjointnessAxiom disjointnessAxiom)

Description copied from interface: Context

Adds one instance of IndexedDisjointnessAxiom to this Context.

Specified by:

addDisjointnessAxiom in interface Context

Parameters:

disjointnessAxiom - the IndexedDisjointnessAxiom to be added to this Context

Returns:

true if adding the axiom changes the state of this Context, i.e., some rules need to be applied

removeDisjointnessAxiom

public boolean removeDisjointnessAxiom(IndexedDisjointnessAxiom axiom)

Description copied from interface: Context

Removes one instance of the given IndexedDisjointnessAxiom from this Context.

Specified by:

removeDisjointnessAxiom in interface Context

Parameters:

axiom - the IndexedDisjointnessAxiom to be removed from this Context

Returns:

true if the state of this Context has changed as the result of calling this method, i.e., the context has contained this IndexedDisjointnessAxiom

containsDisjointnessAxiom

public boolean containsDisjointnessAxiom(IndexedDisjointnessAxiom axiom)

Specified by:

containsDisjointnessAxiom in interface Context

Parameters:

axiom - the IndexedDisjointnessAxiom to be checked for occurrences in this Context

Returns:

true if the given IndexedDisjointnessAxiom occurs in this Context

inconsistencyDisjointnessAxiom

public boolean inconsistencyDisjointnessAxiom(IndexedDisjointnessAxiom axiom)

Specified by:

inconsistencyDisjointnessAxiom in interface Context

Parameters:

axiom - the IndexedDisjointnessAxiom to be checked for causing inconsistency in this Context

Returns:

true if the given IndexedDisjointnessAxiom causes inconsistency of this Context

setSaturated

public boolean setSaturated(boolean saturated)

Description copied from interface: Context

Marks this Context as saturated. This means that all all Conclusions for this Context are already computed.

Specified by:

setSaturated in interface Context

Returns:

the previous value of the saturation state for this Context

isSaturated

public boolean isSaturated()

Specified by:

isSaturated in interface Context

Returns:

true if all Conclusions for this Context, as determined by the function Conclusion.getSourceContext(Context), are already computed.

addBackwardLink

public boolean addBackwardLink(BackwardLink link)

Description copied from interface: Context

Adds the given BackwardLink to this Context.

Specified by:

addBackwardLink in interface Context

Parameters:

link - the BackwardLink being added to this Context

Returns:

true if this Context has changed as the result this method, i.e., the given BackwardLink has not been added before to this Context. This method is not thread safe.

removeBackwardLink

public boolean removeBackwardLink(BackwardLink link)

Specified by:

removeBackwardLink in interface Context

getBackwardLinkRuleChain

public AbstractChain<ModifiableLinkRule<BackwardLink>> getBackwardLinkRuleChain()

Specified by:

getBackwardLinkRuleChain in interface Context

Returns:

the Chain view of all backward link rules assigned to this Context; this is always not null. This method can be used for convenient search and modification (addition and deletion) of the rules using the methods of the Chain interface without without worrying about null values.

getBackwardLinkRuleHead

public ModifiableLinkRule<BackwardLink> getBackwardLinkRuleHead()

Specified by:

getBackwardLinkRuleHead in interface Context

Returns:

the first backward link rule assigned to this Context, or null if there no such rules; all other rules can be obtained by traversing over Link.next(); this method should be used to access the rules without modifying them.

addToDo

public boolean addToDo(Conclusion conclusion)

Description copied from interface: Context

Adds the given Conclusion to be processed within this Context. The method returns true when this is the first unprocessed conclusion added to the context after it is being created or cleared (that is, Context.takeToDo() has returned null). If several threads call this method at the same time for the same Context then at most one of these method returns true, unless Context.takeToDo() is called as well.

Specified by:

addToDo in interface Context

Parameters:

conclusion - the Conclusion added to be processed within this Context

Returns:

true when the added conclusion is the first unprocessed conclusion for this context

See Also:

Context.takeToDo()

takeToDo

public Conclusion takeToDo()

Description copied from interface: Context

Removes and returns one of the unprocessed Conclusions of this context. This method is thread safe and can be used concurrently with the method Context.addToDo(Conclusion).

Specified by:

takeToDo in interface Context

Returns:

some unprocessed Conclusion of this context, if there is one, or null if there is no such Conclusion

See Also:

Context.addToDo(Conclusion)

toString

public String toString()

Overrides:

toString in class Object

isEmpty

public boolean isEmpty()

Specified by:

isEmpty in interface Context

Returns:

true if the context is empty