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Triple Stores

Triple stores are specialized databases designed to store and manage RDF triples. They support various RDF query languages, with SPARQL being the W3C recommendation. While some may offer inferencing capabilities, many main query languages do not handle inserts. Triple stores can be implemented in-memory or utilize persistent backends, such as relational databases for efficiency. Prominent examples include HP's Jena Framework, Kowari, and Sesame, each offering unique features for metadata storage, retrieval, and analysis. This overview addresses performance, scalability, and integration with conventional RDBMS technology.

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Triple Stores

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  1. Triple Stores

  2. What is a triple store? • A specialized database for RDF triples • Supports a query language • SPARQL is the W3C recommendation • Other RDF query languages exist (e.g., RDQL) • Might or might not do inferencing • Most query languages don’t handle inserts • Triple stores might be in memory or provide a persistent backend • Presistence provided by a relational DBMS (e.g., mySQL) or a custom DB for efficiency.

  3. Example: HP’s Jena Framework • An OS Java system developed by HP • http://jena.sourceforge.net/ • Has internal reasoners and can work with DIG compliant reasoners or Pellet. • Supports SPARQL • Joseki is an add-on that provides a SPARQL endpoint via an HTTP interface

  4. SPARQL Example BASE <http://example.org/> PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> PREFIX foaf: <http://xmlns.com/foaf/0.1/> PREFIX ex: <properties/1.0#> SELECT DISTINCT $person ?name $age FROM <http://rdf.example.org/people.rdf> WHERE { $person a foaf:Person ; foaf:name ?name. OPTIONAL { $person ex:age $age } . FILTER ! REGEX(?name, "Bob") } LIMIT 3 ORDER BY ASC[?name]

  5. Example: Kowari • http://kowari.org/ • “An Open Source, massively scalable, transaction-safe, purpose-built database for the storage, retrieval and analysis of metadata” • Implemented in Java, not built on a conventional RDBMS • Developed by Tucana, which also had a commercial version • Tucana closed down in Fall 2005, Northrop Grumman purchased the rights to the commercial system

  6. Example: Sesame • Sesame is an open source RDF framework with support for RDFS inferencing and querying • http://www.openrdf.org/ • Implemented in Java • Query languages: SeRQL, RQL, RDQL • Triples can be stored in memory, on disk, or in a RDBMS

  7. Issues • Can we build efficient triple stores around conventional RDBMS technology? • What are the performance issues? • Load time? • Interfencing? • How well does is scale?

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