edu.rpi.twc.sesamestream.impl

Class QueryEngineImpl

java.lang.Object

edu.rpi.twc.sesamestream.impl.QueryEngineImpl

All Implemented Interfaces:

QueryEngine

public class QueryEngineImpl
extends Object
implements QueryEngine

Concrete implementation of a SesameStream continuous SPARQL query engine. The engine receives SPARQL queries in advance of the data they query against, and answers them in a forward-chaining fashion. Optionally (depending on SesameStream settings), performance data is generated in the process. Current assumptions: 1) only simple, conjunctive SELECT queries, without filters, unions, optionals, etc. 2) no GRAPH constraints 3) no duplicate queries 4) no duplicate statements 5) no duplicate triple patterns in a query 6) single query at a time 7) no combo of queries and statements such that multiple triple patterns match the same statement 8 queries are only added, never removed 9) statements are only added, never removed 10) a statement will never match more than one triple pattern, per query, at a time

Author:

Joshua Shinavier (http://fortytwo.net)

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
class	QueryEngineImpl.TriplePatternDeduplicator An object to ensure that triple patterns created by replacement are not duplicates

Nested classes/interfaces inherited from interface edu.rpi.twc.sesamestream.QueryEngine

QueryEngine.IncompatibleQueryException, QueryEngine.InvalidQueryException

Constructor Summary

Constructors

Constructor and Description
QueryEngineImpl() Creates a new query engine with an empty index

Method Summary

Modifier and Type	Method and Description
Subscription	addQuery(String q, BindingSetHandler h)
Subscription	addQuery(org.openrdf.query.algebra.TupleExpr t, BindingSetHandler h) Adds a new query subscription to this query engine
void	addStatement(org.openrdf.model.Statement s)
void	addStatements(Collection<org.openrdf.model.Statement> statements)
void	addStatements(org.openrdf.model.Statement... statements)
void	clear()
TripleIndex	getIndex() Gets the index, or in-memory database, of this query engine
void	setLinkedDataCache(net.fortytwo.linkeddata.LinkedDataCache cache, org.openrdf.sail.Sail sail) Adds a Linked Data fetching and caching layer to this query engine.

Methods inherited from class java.lang.Object

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

Constructor Detail

QueryEngineImpl

public QueryEngineImpl()

Creates a new query engine with an empty index

Method Detail

setLinkedDataCache

public void setLinkedDataCache(net.fortytwo.linkeddata.LinkedDataCache cache,
                               org.openrdf.sail.Sail sail)
                        throws org.openrdf.sail.SailException

Adds a Linked Data fetching and caching layer to this query engine. Once added, the Linked Data cache will listen for new triple patterns indexed by this query engine, and issue corresponding HTTP requests for additional information about URIs in those patterns. Any RDF statements from retrieved documents are passed into the query engine, where they may contribute to query results and/or partial solutions, and may trigger further HTTP requests.

Parameters:

cache - a collection of caching metadata about Linked Data already retrieved

sail - the RDF component of the caching metadata

Throws:

org.openrdf.sail.SailException - if a cache-level query exception occurs

getIndex

public TripleIndex getIndex()

Gets the index, or in-memory database, of this query engine

Returns:

the index, or in-memory database, of this query engine. It should not be necessary to interact with the index directly, but it is possible to inspect the index via print and visit methods.

clear

public void clear()

Specified by:

clear in interface QueryEngine

addQuery

public Subscription addQuery(String q,
                             BindingSetHandler h)
                      throws QueryEngine.IncompatibleQueryException,
                             QueryEngine.InvalidQueryException

Specified by:

addQuery in interface QueryEngine

Throws:

QueryEngine.IncompatibleQueryException

QueryEngine.InvalidQueryException

addQuery

public Subscription addQuery(org.openrdf.query.algebra.TupleExpr t,
                             BindingSetHandler h)
                      throws QueryEngine.IncompatibleQueryException

Adds a new query subscription to this query engine

Parameters:

t - the query to add

h - a handler for future query answers

Returns:

a subscription for computation of future query answers

Throws:

IncompatibleQueryException - if the syntax of the query is not supported by this engine

QueryEngine.IncompatibleQueryException

addStatement

public void addStatement(org.openrdf.model.Statement s)

Specified by:

addStatement in interface QueryEngine

addStatements

public void addStatements(org.openrdf.model.Statement... statements)

Specified by:

addStatements in interface QueryEngine

addStatements

public void addStatements(Collection<org.openrdf.model.Statement> statements)

Specified by:

addStatements in interface QueryEngine