Module system-core

Connectors, Connections, and Statements

The main interface is DBConnector, a closeable factory for OntopConnections and, from them, OntopStatement, which mirror the JDBC Connection and Statement abstractions. Interface OntopQueryEngine provide similar facilities of DBConnector and its implmentation OntopQueryEngineImpl indeed delegates to a DBConnector instance.

DBConnector and related interfaces are implemented differently based on queried backend, and GUICE factory OntopSystemFactory allows creating both DBConnectors and OntopQueryEngine based on configurated implementations.

Abstract class QuestStatement provids a skeletical implementation of OntopStatement which leverages QueryReformulator.reformulateNativeQuery() to process the input query.

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Result Set Implementations

Classes DefaultSimpleGraphResultSet and PredefinedBooleanResultSet provide default implementations for graph and boolean queries, the first delegating to a TupleResultSet.

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Materialization

Interface OntopRDFMaterializer and associated MaterializationParams can be instantiated via static methods / builders and provide support for materializing the virtual RDF graph (MaterializedGraphResultSet) obtained via OBDA. Its implementation leverage an instance of OntopQueryEngine obtained through GUICE.

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Query Manager

Package querymanager provide data model classes for representing a collections of groups (QueryControllerQuery) of queries (QueryControllerGroup) that can be manipulated (added, removed, edited) with listener modification. The package is used by the protege Maven module.

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Version Info

Singleton class VersionInfo provides access to Ontop version information read from a properties resource.

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Remarks

• one among DBConnector and OntopQueryEngine seems redundant
• OntopConnection and OntopStatement extend interfaces OBDAConnection and OBDAStatement, which are never used alone and thus appear as redundant
• materialization may be offered as an additional service of OntopConnection / OntopStatement (see, e.g., how RDF export in RDF4J is offered at connection level and not through a separate component delegating to a connection)
• it's unclear why querymanager code is placed in the system-core module