com.bigdata.rdf.sparql.ast.cache

Class DescribeCacheUpdater

java.lang.Object

com.bigdata.rdf.sparql.ast.cache.DescribeCacheUpdater

All Implemented Interfaces:

info.aduna.iteration.CloseableIteration<BigdataStatement,org.openrdf.query.QueryEvaluationException>, info.aduna.iteration.Iteration<BigdataStatement,org.openrdf.query.QueryEvaluationException>

public class DescribeCacheUpdater
extends Object
implements info.aduna.iteration.CloseableIteration<BigdataStatement,org.openrdf.query.QueryEvaluationException>

Collects statements written onto the RDFWriter interface and adds/replaces the DESCRIBE of the Resource specified to the constructor.

Author:

Bryan Thompson

Constructor Summary

Constructors

Constructor and Description
DescribeCacheUpdater(IDescribeCache cache, Set<BigdataValue> describedResources, info.aduna.iteration.CloseableIteration<BigdataStatement,org.openrdf.query.QueryEvaluationException> src)

Method Summary

Methods

Modifier and Type	Method and Description
void	close()
boolean	hasNext()
BigdataStatement	next() TODO In order to support CBD, we will also have to recognize statements that describe blank nodes that are part of the description of a described resource as belonging to that described resource.
void	remove()

Methods inherited from class java.lang.Object

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

Constructor Detail

DescribeCacheUpdater

public DescribeCacheUpdater(IDescribeCache cache,
                    Set<BigdataValue> describedResources,
                    info.aduna.iteration.CloseableIteration<BigdataStatement,org.openrdf.query.QueryEvaluationException> src)

Parameters:

cache - The cache to be updated.

describedResources - The BigdataValues that become bound for the projection of the original DESCRIBE query. We will collect all statements having a described resource as either a subject or an object. This MUST be a thread-safe (and concurrency favorable) set in order to ensure the visibility of the updates.

src - The source iterator, visiting the statements that are the description of the resource(s) identified in the ProjectionNode.

Method Detail

hasNext

public boolean hasNext()
                throws org.openrdf.query.QueryEvaluationException

Specified by:

hasNext in interface info.aduna.iteration.Iteration<BigdataStatement,org.openrdf.query.QueryEvaluationException>

Throws:

org.openrdf.query.QueryEvaluationException

next

public BigdataStatement next()
                      throws org.openrdf.query.QueryEvaluationException

TODO In order to support CBD, we will also have to recognize statements that describe blank nodes that are part of the description of a described resource as belonging to that described resource. This is necessary in order to capture the transitive closure of the resource description specified by CBD. The code in this method only recognizes statements that directly have a described resource as a subject or object. We probably need a reverse map that will allow us to navigate from a BigdataValue (or perhaps just a BigdataBNode) to all described resources for which that value was observed. That map might only need to contain the blank nodes since the description can never expand beyond a statement having a blank node in the subject (or object) position and a non-blank node in the object (or subject) position.

Specified by:

next in interface info.aduna.iteration.Iteration<BigdataStatement,org.openrdf.query.QueryEvaluationException>

Throws:

org.openrdf.query.QueryEvaluationException

See Also:

Concise Bounded Description

close

public void close()
           throws org.openrdf.query.QueryEvaluationException

Specified by:

close in interface info.aduna.iteration.CloseableIteration<BigdataStatement,org.openrdf.query.QueryEvaluationException>

Throws:

org.openrdf.query.QueryEvaluationException

remove

public void remove()
            throws org.openrdf.query.QueryEvaluationException

Specified by:

remove in interface info.aduna.iteration.Iteration<BigdataStatement,org.openrdf.query.QueryEvaluationException>

Throws:

org.openrdf.query.QueryEvaluationException