RDB2RDF Working Group Charter
Revised February 24, 2009In the last few years there has been increasing interest in mapping Relational data to the Semantic Web. This is to allow Relational data to be combined with other data on the Web, to add semantics to Relational data and to aid in enterprise data integration. In October 2007, the W3C organized a workshop on RDF Access to Relational Databases. This led to the formation of the RDB2RDF Incubator Group to explore the area. This Incubator Group recently concluded its work and produced two deliverables: a Survey of the State of the Art and a RDB2RDF XG Final Report. The RDB2RDF XG Final Report. recommends that the W3C initiate a Working Group to standardize a language for mapping Relational database schemas to RDF and OWL. This charter is a follow-up to that recommendation.
Consequently, the mission of the RDB2RDF Working Group, part of the Semantic Web Activity, is to standardize a language for mapping Relational Database schemas into RDF and OWL: the RDB2RDF Mapping Language (R2RML).
The mapping language defined by the WG would facilitate the development of several types of products. It could be used to translate Relational data into RDF which could be stored in a triple store. This is sometimes called Extract-Transform-Load (ETL). Or it could be used to generate a virtual mapping that could be queried using SPARQL and the SPARQL translated to SQL queries on the underlying Relational data. Other products could be layered on top of these capabilities to query and deliver data in different ways as well as to integrate the data with other kinds of information on the Semantic Web. The RDB2RDF XG Final Report includes several detailed usecases that motivate the mapping language.
| End date | 30 June 2011 (two years from inception) |
|---|---|
| Confidentiality | Proceedings are public |
| Initial Chairs | CHAIR INFO |
| Initial Team Contacts (FTE %: 5 to 10) | TEAM CONTACT INFO |
| Usual Meeting Schedule | Teleconferences: Weekly
Face-to-face: 3-4 per year |
Scope
Based on the Survey of Current Approaches for Mapping of Relational Databases to RDF prepared by the RDB2RDF XG and the RDB2RDF XG Final Report the scope of R2RML is defined as follows:
- The mapping language MUST define the mapping of Relational schemas to RDF and OWL.
- The mapping language SHOULD be complete with regard to the Relational algebra, i.e. all Relational constructs SHOULD be expressible in the language.
- The mapping language SHOULD have a human-readable syntax as well as XML and RDF representations of the syntax for purposes of discovery and machine generation.
- The mapping language SHOULD be expressed in rules as defined by the W3C RIF WG. The syntax need not follow the RIF syntax but there SHOULD exist a round-tripable transformation between the mapping language and an RIF dialect.
- It SHOULD be possible to subset the mapping language for lightweight applications such as Web 2.0 applications. This feature of the language will be validated by creating a library of mappings for widely used applications such as Drupal, Wordpress and phpBB.
- The mapping language MUST allow customization with regard to names and data transformation. In addition the language MUST allow the addition of rules and RDF constraints as part of the mapping.
- The language must be able to expose vendor specific SQL features such as full-text and spatial support and vendor-defined datatypes.
- The mapping language specification SHOULD include guidance with regard to mapping Relational data to a subset of OWL such as OWL/QL or OWL/RL.
- The mapping language MUST allow for a mechanism to create identifiers for database entities. The generation of identifiers should be designed to support the implementation of the linked data principles. Where possible, the language will encourage the reuse of public identifiers for long-lived entities such as persons, corporations and geo-locations.
The Survey of the State of the Art describes several languages and implementations that may be used as starting points for the work of the WG.
Success Criteria
- Timely preparation of the deliverables. See below.
- At least two conforming implementations of the mapping language, perhaps embedded into products that provide additional functionality.
Out of Scope
- Mapping from non-Relational data to RDF and OWL.
- Updating the Relational Database based on changes to the RDF or OWL.