Framework overview

The SPARQL2XQuery Framework allows the transformation of SPARQL queries in XQuery expressions. It has been integrated with the XS2OWL framework, which allows the transformation of XML Schema into OWL syntax.

The architecture of the SPARQL2XQuery framework is depicted in the figure below. The SPARQL2XQuery framework provides interoperability and integration between the Semantic Web (OWL/RDF/SPARQL) and the XML (XML Schema/XML/XQuery) environments. The SPARQL2XQuery framework supports two different scenarios:

1^st Scenario: Querying XML data based on existing ontologies. In this scenario, existing ontologies are manually mapped to XML Schemas.

1. Existing ontologies are manually mapped (by an expert) to the XML Schema(s).
2. The SPARQL queries expressed over the existing ontologies are translated to XQuery expressions.
3. The query results are transformed into the desired format (SPARQL Query Result XML Format or RDF).

2^nd Scenario: Querying XML data based on an automatically generated ontology.

1. Using the XS2OWL framework, the XML Schema is automatically transformed to an OWL ontology.
2. The SPARQL2XQuery framework, takes as input the XML Schema and the generated ontology and it automatically generates, maintains and stores (as XML documents) the mappings between them.
3. The SPARQL queries posed over the generated ontology are translated to XQuery expressions.
4. The query results are transformed into the desired format (format (SPARQL Query Result XML Format or RDF).

Framework components

• Schema Transformation:
  XML Schema to OWL syntax by using the XS2OWL framework.
• Mappings Generation:
  The mappings between the OWL representations of the XML Schemas and the XML Schemas can be automatically detected or manually specified and stored as XML documents.
• Mappings Specification:
  Mappings between OWL-RDF/S ontologies and XML Schemas can be manually specified and used in the SPARQL to XQuery translation.
• Query Translation:
  SPARQL-to-XQuery. Every SPARQL query that is posed over the ontologies is translated with respect to the predefined mappings into an XQuery query.
• Query Results Transformation:
  The query results are transformed into the desired SPARQL Query Result XML Format or in RDF format.
• XML - RDF Transformation:
  Transformation of XML documents in RDF syntax and vice versa.

Project Timeline

The SPARQL2XQuery Framework was introduced in 2009 and is being regularly updated till now, according to the related updates of the W3C standards in order to capture and support any new features and functionality.

Publications

• SPARQL2XQuery 2.0: Supporting Semantic-based Queries over XML Data

  I. Stavrakantonakis, C. Tsinaraki, N. Bikakis, N. Gioldasis, S. Christodoulakis

  -In the proceedings of SMAP 2010, pp. 76-84.

• Querying XML Data with SPARQL

  Bikakis N., Gioldasis N., Tsinaraki C., Christodoulakis S.

  -In the proceedings of the 20th International Conference on Database and Expert Systems Applications DEXA '09 2009

• Semantic Based Access over XML Data

  Bikakis N., Gioldasis N., Tsinaraki C., Christodoulakis S.

  -In the Proceedings of the 2nd World Summit on the Knowledge Society, Crete, Greece 2009

Theses

• Interoperability support between OWL 2.0 and XML environments

  I. Stavrakantonakis - Diploma Thesis - 2011

• Supporting Semantic Queries over XML Databases

  N. Bikakis - Diploma Thesis - 2009