ISSUE-25: Including direct mapping constructs in R2RML mappings

Direct mapping in custom mappings

Including direct mapping constructs in R2RML mappings

State:
CLOSED
Product:
R2RML
Raised by:
David McNeil
Opened on:
2011-03-01
Description:
The R2RML editor's draft, http://www.w3.org/2001/sw/rdb2rdf/r2rml/#sql-conformance, identifies this issue:

"The use of a 'convention over configuration' approach has been proposed, where a mapping is not expressed completely, but rather as a delta from the default mapping. In other words, only those parts that one wants to be different from the default mapping have to be written down in the mapping file."

An approach has been discussed in which a custom mapping can specify that the direct mapping should be used for some database elements. This would "expand" in the custom mapping and provide the direct mapping defined constructs without requiring the user to define them explicitly.

While I can see the benefit of this approach I think it would be better to start with a simpler specification that does not tie the R2RML specification to the Direct Mapping specification in this way. This provides several benefits:

* R2RML mappings are easier to understand (the Direct Mapping specification does not need to be referenced to understand a custom mapping)
* R2RML is easier to implement without the ties to the Direct Mapping
* it is easier to implement R2RML in a consistent manner (differences in interpretation of the Direct Mapping spec do not leak into the implementation of R2RML itself)
* this keeps contentious issues related to automatic blank node generation and URI generation out of R2RML (otherwise these issues leak into R2RML via the Direct Mapping support)
* this approach allows the W3C, users, and vendors the chance to gain more experience with R2RML mappings before attempting to define standard default mappings that are a part of R2RML
Related Actions Items:
Related emails:
  1. Minutes of 2011-05-03 telecon (from michael.hausenblas@deri.org on 2011-05-03)
  2. Re: Agenda for RB2RDF Teleconference Aprrl 26, 2011 (from seema.sundara@oracle.com on 2011-04-26)
  3. Re: Keeping R2RML free of Direct Mapping dependency (ISSUE-25) (from juanfederico@gmail.com on 2011-04-26)
  4. Re: Keeping R2RML free of Direct Mapping dependency (ISSUE-25) (from ivan@w3.org on 2011-04-26)
  5. Re: Keeping R2RML free of Direct Mapping dependency (ISSUE-25) (from juanfederico@gmail.com on 2011-04-26)
  6. Re: Keeping R2RML free of Direct Mapping dependency (ISSUE-25) (from ivan@w3.org on 2011-04-26)
  7. Re: Keeping R2RML free of Direct Mapping dependency (ISSUE-25) (from bertails@w3.org on 2011-04-26)
  8. Re: Keeping R2RML free of Direct Mapping dependency (ISSUE-25) (from dmcneil@revelytix.com on 2011-04-26)
  9. Re: Keeping R2RML free of Direct Mapping dependency (ISSUE-25) (from ivan@w3.org on 2011-04-26)
  10. Re: Keeping R2RML free of Direct Mapping dependency (ISSUE-25) (from bertails@w3.org on 2011-04-26)
  11. Re: Keeping R2RML free of Direct Mapping dependency (ISSUE-25) (from dmcneil@revelytix.com on 2011-04-26)
  12. Re: Keeping R2RML free of Direct Mapping dependency (ISSUE-25) (from ivan@w3.org on 2011-04-26)
  13. Re: Keeping R2RML free of Direct Mapping dependency (ISSUE-25) (from ivan@w3.org on 2011-04-26)
  14. Re: Agenda for RB2RDF Teleconference Aprrl 26, 2011 (from souripriya.das@oracle.com on 2011-04-26)
  15. Re: Agenda for RB2RDF Teleconference Aprrl 26, 2011 (from soeren.auer@gmail.com on 2011-04-26)
  16. Re: D2R's many-to-many definition (from michael.hausenblas@deri.org on 2011-04-26)
  17. Re: Keeping R2RML free of Direct Mapping dependency (ISSUE-25) (from dmcneil@revelytix.com on 2011-04-26)
  18. Re: Agenda for RB2RDF Teleconference Aprrl 26, 2011 (from marcelo.arenas1@gmail.com on 2011-04-26)
  19. D2R's many-to-many definition (from eric@w3.org on 2011-04-26)
  20. Re: Keeping R2RML free of Direct Mapping dependency (ISSUE-25) (from dmcneil@revelytix.com on 2011-04-26)
  21. Re: Keeping R2RML free of Direct Mapping dependency (ISSUE-25) (from ivan@w3.org on 2011-04-26)
  22. Re: Keeping R2RML free of Direct Mapping dependency (ISSUE-25) (from dmcneil@revelytix.com on 2011-04-26)
  23. Re: Keeping R2RML free of Direct Mapping dependency (ISSUE-25) (from ivan@w3.org on 2011-04-26)
  24. Re: Agenda for RB2RDF Teleconference Aprrl 26, 2011 (from michael.hausenblas@deri.org on 2011-04-25)
  25. Agenda for RB2RDF Teleconference Aprrl 26, 2011 (from ashok.malhotra@oracle.com on 2011-04-25)
  26. Keeping R2RML free of Direct Mapping dependency (ISSUE-25) (from dmcneil@revelytix.com on 2011-04-19)
  27. Minutes of 2011-04-19 telecon (from michael.hausenblas@deri.org on 2011-04-19)
  28. Issues mentioned in R2RML draft (from richard@cyganiak.de on 2011-03-22)
  29. Re: RDB2RDF WG agenda for 2011-03-08 meeting 1700 UTC (from michael.hausenblas@deri.org on 2011-03-08)
  30. Re: RDB2RDF WG agenda for 2011-03-08 meeting 1700 UTC (from bertails@w3.org on 2011-03-07)
  31. RDB2RDF WG agenda for 2011-03-08 meeting 1700 UTC (from michael.hausenblas@deri.org on 2011-03-06)
  32. ISSUE-25 (Direct mapping in custom mappings): Including direct mapping constructs in R2RML mappings (from sysbot+tracker@w3.org on 2011-03-01)

Related notes:

as of http://www.w3.org/2011/05/03-rdb2rdf-minutes.html#item06 can be closed once ACTION-123 is done

Michael Hausenblas, 3 May 2011, 16:54:22

The WG decision was: Resolve ISSUE-25 with 'if tables and columns are not mentioned in the R2R mapping, they will not be mapped. Specifically, the DM semantics will not be used to map these tables and columns.' 1. update R2RML document accordingly. 2. at this time the R2RML mapping language will not include a property to invoke the direct mapping.

This was implemented in ACTION-123.

Richard Cyganiak, 29 Jun 2011, 08:17:26

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Ashok Malhotra <ashok.malhotra@oracle.com>, Michael Hausenblas <michael.hausenblas@deri.org>, Chairs, Eric Prud'hommeaux <eric@w3.org>, Ivan Herman <ivan@w3.org>, Staff Contacts
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