ISSUE-42: How is the direct mapping suppose to handle NULL values wrt Information Preserving

null handling direct mapping

How is the direct mapping suppose to handle NULL values wrt Information Preserving

State:
CLOSED
Product:
Direct Mapping
Raised by:
Juan Sequeda
Opened on:
2011-05-18
Description:
Currently, the direct mapping completely ignores NULL values. In other words, no triples are generated for NULL values. This seems to be the expected output.

However there seems to an issue when it comes to Information Preserving.

If the direct mapping considers the schema, then there is no need to translate NULLs in order for the mapping to be information preserving. However, if the schema is not considered, the mapping is not information preserving. Currently, the direct mapping does not consider the schema.

For an example, please see:
http://lists.w3.org/Archives/Public/public-rdb2rdf-wg/2011May/0049.html
Related Actions Items:
No related actions
Related emails:
  1. Re: RDB2RDF WG agenda for 2011-08-09 meeting 1600 UTC (from ashok.malhotra@oracle.com on 2011-08-09)
  2. Comments and suggestions regarding the 'A Direct Mapping of Relational Data to RDF' (from michael.hausenblas@deri.org on 2011-08-09)
  3. RDB2RDF WG agenda for 2011-08-09 meeting 1600 UTC (from michael.hausenblas@deri.org on 2011-08-06)
  4. Re: My mistake in the ISSUE-42 resolution (was: Re: a rigorous review of http://www.w3.org/2001/sw/rdb2rdf/wiki/RDBNullValues#Direct_Mapping) (from michael.hausenblas@deri.org on 2011-06-18)
  5. My mistake in the ISSUE-42 resolution (was: Re: a rigorous review of http://www.w3.org/2001/sw/rdb2rdf/wiki/RDBNullValues#Direct_Mapping) (from richard@cyganiak.de on 2011-06-18)
  6. Re: a rigorous review of http://www.w3.org/2001/sw/rdb2rdf/wiki/RDBNullValues#Direct_Mapping (from eric@w3.org on 2011-06-17)
  7. Re: a rigorous review of http://www.w3.org/2001/sw/rdb2rdf/wiki/RDBNullValues#Direct_Mapping (from franconi@inf.unibz.it on 2011-06-17)
  8. Re: a rigorous review of http://www.w3.org/2001/sw/rdb2rdf/wiki/RDBNullValues#Direct_Mapping (from ivan@w3.org on 2011-06-17)
  9. Minutes of 2011-06-14 telecon (from michael.hausenblas@deri.org on 2011-06-14)
  10. Re: Agenda for June 14 Telcon - Revision 1 (from franconi@inf.unibz.it on 2011-06-14)
  11. Re: Agenda for June 14 Telcon - Revision 1 (from michael.hausenblas@deri.org on 2011-06-14)
  12. Re: Agenda for June 14 Telcon - Revision 1 (from franconi@inf.unibz.it on 2011-06-14)
  13. Re: Agenda for June 14 Telcon - Revision 1 (from michael.hausenblas@deri.org on 2011-06-14)
  14. Re: Agenda for June 14 Telcon - Revision 1 (from franconi@inf.unibz.it on 2011-06-14)
  15. Re: Agenda for June 14 Telcon - Revision 1 (from michael.hausenblas@deri.org on 2011-06-14)
  16. Re: Agenda for June 14 Telcon - Revision 1 (from franconi@inf.unibz.it on 2011-06-14)
  17. Re: Agenda for June 14 Telcon - Revision 1 (from michael.hausenblas@deri.org on 2011-06-14)
  18. Re: Agenda for June 14 Telcon - Revision 1 (from franconi@inf.unibz.it on 2011-06-14)
  19. Re: Agenda for June 14 Telcon - Revision 1 (from michael.hausenblas@deri.org on 2011-06-14)
  20. Re: Agenda for June 14 Telcon - Revision 1 (from marcelo.arenas1@gmail.com on 2011-06-14)
  21. Re: Agenda for June 14 Telcon - Revision 1 (from eric@w3.org on 2011-06-13)
  22. Re: Agenda for June 14 Telcon - Revision 1 (from franconi@inf.unibz.it on 2011-06-13)
  23. Re: Agenda for June 14 Telcon - Revision 1 (from ashok.malhotra@oracle.com on 2011-06-13)
  24. Re: Agenda for June 14 Telcon (from juanfederico@gmail.com on 2011-06-13)
  25. Agenda for June 14 Telcon (from ashok.malhotra@oracle.com on 2011-06-13)
  26. Re: Proposed Resolution for Issue 42 (from richard@cyganiak.de on 2011-05-31)
  27. Re: Proposed Resolution for Issue 42 (from juanfederico@gmail.com on 2011-05-31)
  28. Re: Proposed Resolution for Issue 42 (from richard@cyganiak.de on 2011-05-31)
  29. Re: Proposed Resolution for Issue 42 (from bertails@w3.org on 2011-05-31)
  30. Re: Proposed Resolution for Issue 42 (from juanfederico@gmail.com on 2011-05-31)
  31. Re: Proposed Resolution for Issue 42 (from richard@cyganiak.de on 2011-05-31)
  32. Re: RDB2RDF WG agenda for 2011-05-31 meeting 1600 UTC (from marcelo.arenas1@gmail.com on 2011-05-31)
  33. Re: RDB2RDF WG agenda for 2011-05-31 meeting 1600 UTC (from privera.salas@gmail.com on 2011-05-31)
  34. Re: Proposal to resolve ISSUE-22 'vendor specific SQL' (from michael.hausenblas@deri.org on 2011-05-31)
  35. Re: RDB2RDF WG agenda for 2011-05-31 meeting 1600 UTC (from bvillazon@fi.upm.es on 2011-05-30)
  36. RDB2RDF WG agenda for 2011-05-31 meeting 1600 UTC (from michael.hausenblas@deri.org on 2011-05-30)
  37. Re: Q: ISSUE-42 bNode semantics (from franconi@inf.unibz.it on 2011-05-23)
  38. Re: Q: ISSUE-42 bNode semantics (from richard@cyganiak.de on 2011-05-23)
  39. Re: Q: ISSUE-42 bNode semantics (from franconi@inf.unibz.it on 2011-05-23)
  40. Re: Q: ISSUE-42 bNode semantics (from richard@cyganiak.de on 2011-05-23)
  41. Re: Q: ISSUE-42 bNode semantics (from franconi@inf.unibz.it on 2011-05-22)
  42. Re: Q: ISSUE-42 bNode semantics (from richard@cyganiak.de on 2011-05-22)
  43. Re: Q: ISSUE-42 bNode semantics (from franconi@inf.unibz.it on 2011-05-22)
  44. Re: Q: ISSUE-42 bNode semantics (from richard@cyganiak.de on 2011-05-22)
  45. Re: RDB2RDF WG agenda for 2011-05-24 meeting 1600 UTC (from michael.hausenblas@deri.org on 2011-05-22)
  46. Re: RDB2RDF WG agenda for 2011-05-24 meeting 1600 UTC (from bertails@w3.org on 2011-05-21)
  47. Re: Q: ISSUE-42 bNode semantics (from franconi@inf.unibz.it on 2011-05-21)
  48. Re: Q: ISSUE-42 bNode semantics (from franconi@inf.unibz.it on 2011-05-21)
  49. Re: Q: ISSUE-42 bNode semantics (from richard@cyganiak.de on 2011-05-21)
  50. RDB2RDF WG agenda for 2011-05-24 meeting 1600 UTC (from michael.hausenblas@deri.org on 2011-05-21)
  51. Re: Q: ISSUE-42 bNode semantics (from franconi@inf.unibz.it on 2011-05-21)
  52. Re: Q: ISSUE-42 bNode semantics (from richard@cyganiak.de on 2011-05-20)
  53. Re: NULLs and the direct mapping (ISSUE-42) (was: Re: Q: ISSUE-41 bNode semantics) (from richard@cyganiak.de on 2011-05-19)
  54. NULLs and the direct mapping (ISSUE-42) (was: Re: Q: ISSUE-41 bNode semantics) (from richard@cyganiak.de on 2011-05-19)
  55. Re: NULLs and the direct mapping (ISSUE-42) (was: Re: Q: ISSUE-41 bNode semantics) (from dmcneil@revelytix.com on 2011-05-19)
  56. Re: Q: ISSUE-41 bNode semantics (from bertails@w3.org on 2011-05-19)
  57. Re: Q: ISSUE-41 bNode semantics (from bertails@w3.org on 2011-05-19)
  58. Re: Q: ISSUE-41 bNode semantics (from dmcneil@revelytix.com on 2011-05-19)
  59. Re: Information Preserving and ISSUE-42 (from privera.salas@gmail.com on 2011-05-18)
  60. Re: Information Preserving and ISSUE-42 (from juanfederico@gmail.com on 2011-05-18)
  61. Re: Information Preserving and ISSUE-42 (from franconi@inf.unibz.it on 2011-05-18)
  62. Re: Q: ISSUE-41 bNode semantics (from juanfederico@gmail.com on 2011-05-18)
  63. Re: Information Preserving and ISSUE-42 (from juanfederico@gmail.com on 2011-05-18)
  64. Re: Information Preserving and ISSUE-42 (from bertails@w3.org on 2011-05-18)
  65. Re: Information Preserving and ISSUE-42 (from bertails@w3.org on 2011-05-18)
  66. Re: Information Preserving and ISSUE-42 (from juanfederico@gmail.com on 2011-05-18)
  67. Re: Information Preserving and ISSUE-42 (from marcelo.arenas1@gmail.com on 2011-05-18)
  68. Re: Information Preserving and ISSUE-42 (from bertails@w3.org on 2011-05-18)
  69. Re: Information Preserving and ISSUE-42 (from richard@cyganiak.de on 2011-05-18)
  70. Re: [ISSUE-41 and ISSUE-42] What do people think of NULLs (from michael.hausenblas@deri.org on 2011-05-18)
  71. Re: [ISSUE-41 and ISSUE-42] What do people think of NULLs (from franconi@inf.unibz.it on 2011-05-18)
  72. Re: Information Preserving and ISSUE-42 (from franconi@inf.unibz.it on 2011-05-18)
  73. Re: Information Preserving and ISSUE-42 (from ivan@w3.org on 2011-05-18)
  74. Re: Information Preserving and ISSUE-42 (from ivan@w3.org on 2011-05-18)
  75. ISSUE-42 (null handling direct mapping): How is the direct mapping suppose to handle NULL values wrt Information Preserving [Direct Mapping] (from sysbot+tracker@w3.org on 2011-05-18)
  76. Re: Information Preserving and ISSUE-42 (from juanfederico@gmail.com on 2011-05-17)
  77. [ISSUE-41 and ISSUE-42] What do people think of NULLs (from juanfederico@gmail.com on 2011-05-17)
  78. Information Preserving and ISSUE-42 (from juanfederico@gmail.com on 2011-05-17)

Related notes:

See also http://www.w3.org/2001/sw/rdb2rdf/wiki/RDBNullValues

Michael Hausenblas, 19 May 2011, 08:42:05

RESOLUTION: Re ISSUE-42, the WG decides add to the Direct Mapping spec the generating of rdfs:range (and possibly other) schema triples and also add a note to the Direct Mapping spec saying: "The DM does not generate triples for NULL values. For a detailed discussion of this issue, see the following document" which points to a separate working group note

http://www.w3.org/2011/06/14-rdb2rdf-minutes.html

Richard Cyganiak, 9 Aug 2011, 16:52:57

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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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