Implementability for tables w/o primary key

Thanks, Juan, for sending this out.  Could WG members reply indicating whether
they can live with this proposal.    Perhaps we can get this issue resolved by email.
All the best, Ashok

On 5/1/2012 11:55 AM, Juan Sequeda wrote:
> All,
>
> Wrt to the issue "Implementability for tables w/o primary key", I present the following proposal
>
> PROPOSAL: In the DM spec, replace the following text:
>
> [[
> If the table has no primary key, the row node is a fresh blank node that is unique to this row.
> ]]
>
> with this:
>
> [[
>
> If the table has no primary key, the row node is a blank node. Distinct blank nodes MUST be generated for rows with distinct column values. For duplicate rows with identical values, implementations SHOULD generate a fresh blank for each duplicate row (resulting in a non-lean RDF graph [RDF Semantics]). However, if the underlying database system does not provide any means to reliably differentiate among the rows, then implementations MAY re-use the same blank node for multiple duplicate rows (resulting in a lean RDF graph). The lean version does not maintain the relational table's cardinalities, and hence gives different answers under certain SPARQL queries. Implementations MUST document and advertise their chosen behavior.
>
> ]]
>
>
> I believe this proposal is a compromise which will allows both types of implementations.
>
> Juan Sequeda
> +1-575-SEQ-UEDA
> www.juansequeda.com <http://www.juansequeda.com>
>
>
> On Tue, May 1, 2012 at 12:34 PM, Michael Hausenblas <michael.hausenblas@deri.org <mailto:michael.hausenblas@deri.org>> wrote:
>
>     All,
>
>     The minutes of today's meeting are available for review at [1]. We have resolved all but one issue (Implementability for tables w/o primary key) which mainly Eric, Richard and Juan are trying to resolve till next week over the mailing list.
>
>     Cheers,
>               Michael
>
>
>     [1] http://www.w3.org/2012/05/01-RDB2RDF-minutes.html
>
>
>     The WG has taken the following resolutions at today's call:
>
>     ===
>     Re: Fixing an omission in R2RML: syntax of blank node labels (http://lists.w3.org/Archives/Public/public-rdb2rdf-wg/2012Apr/0060.html):
>
>     RESOLUTION: Change Section 11.2 of R2RML http://www.w3.org/TR/2012/CR-r2rml-20120223/#generated-rdf-term)  to:
>
>     [[
>     If the term type is rr:BlankNode: Return a blank node that is unique to the natural RDF lexical form corresponding to value.
>
>     NOTE: RDF syntaxes and RDF APIs generally represent blank nodes with blank node identifiers. But the characters allowed in blank node identifiers differ between syntaxes, and not all characters occurring in value may be allowed, so a bijective mapping function from values to valid blank node identifiers may be required. The details of this mapping function are implementation-dependent, and an R2RML processors may have to use different functions for
>     different output syntaxes or access interfaces. Strings matching the regular expression [a-zA-Z_][a-zA-Z_0-9-]* are valid blank node identifiers in all W3C-recommended RDF syntaxes.
>     ]]
>
>
>     ===
>     Re: Using non-existing column in mapping (http://lists.w3.org/Archives/Public/public-rdb2rdf-wg/2012Apr/0018.html)
>
>     RESOLUTION: No change.
>
>
>     ===
>     Re: Unnamed columns in rr:sqlQuery http://lists.w3.org/Archives/Public/public-rdb2rdf-wg/2012Apr/0017.html
>
>     RESOLUTION: Change Section 5.2 of the R2RML spec (http://www.w3.org/TR/2012/CR-r2rml-20120223/#r2rml-views) to:
>
>     [[
>     Any columns in the SELECT list derived by projecting an expression SHOULD be named.
>     ]]
>
>
>     ===
>     Re: XSD mapping for binary columns (xsd:hexBinary vs. xsd:base64Binary) http://lists.w3.org/Archives/Public/public-rdb2rdf-wg/2012Apr/0020.html
>
>
>     RESOLUTION: Binary datatypes like BLOB and VARBINARY should be mapped to xsd:hexBinary instead of xsd:base64Binary.
>
>
>     ===
>     Re: DM cannot be implemented as an R2RML mapping (period encoding) http://lists.w3.org/Archives/Public/public-rdb2rdf-wg/2012Apr/0021.html
>
>     RESOLUTION: The WG agrees to go with http://lists.w3.org/Archives/Public/public-rdb2rdf-wg/2012Apr/0070.html
>
>
>
>     --
>     Dr. Michael Hausenblas, Research Fellow
>     DERI - Digital Enterprise Research Institute
>     NUIG - National University of Ireland, Galway
>     Ireland, Europe
>     Tel.: +353 91 495730 <tel:%2B353%2091%20495730>
>     WebID: http://sw-app.org/mic.xhtml#i
>
>
>