Re: ISSUE-9 (bn_directmapping): Generate Blank Nodes for duplicate tuples [Direct Mapping]

Hi Everybody,

Marcelo and I have worked out this issue by adding two built in predicates:
card, and <=. These are described in [1]. We have currently written them out
in the case 4.1.3 (Generating Table Triples: table does not have a primary
key) [2] and in case 4.2.3 (Generating Literal Triples: table does not have
a primary key) [3].

We are currently working on section 4.3 Generating Reference Triples.

[1] http://www.w3.org/2001/sw/rdb2rdf/directMapping/#direct_mapping_rules
[2]
http://www.w3.org/2001/sw/rdb2rdf/directMapping/#rules_table_triples_no_pk
[3]
http://www.w3.org/2001/sw/rdb2rdf/directMapping/#rules_literal_triples_no_pk

Juan Sequeda
+1-575-SEQ-UEDA
www.juansequeda.com


On Fri, Jan 21, 2011 at 2:41 PM, RDB2RDF Working Group Issue Tracker <
sysbot+tracker@w3.org <sysbot%2Btracker@w3.org>> wrote:

>
> ISSUE-9 (bn_directmapping): Generate Blank Nodes for duplicate tuples
> [Direct Mapping]
>
> http://www.w3.org/2001/sw/rdb2rdf/track/issues/9
>
> Raised by: Juan Sequeda
> On product: Direct Mapping
>
> Given a table that does not have a primary key, which has duplicate tuples,
> a different blank node must be created for each tuple.
>
> In the Direct Mapping as rules section of the Direct Mapping document, we
> described this scenario by using all the values of the tuple to create the
> blank node [1] [2]. However, there is a bug, raised by Alexandre [3]. The
> issue is that datalog cannot deal with duplicate. Consequently, Marcelo
> raised the point that we can use simple versions of datalog that can deal
> with duplicate solutions.
>
> Possible solutions:
>
> 1) assume that each table implicitly has a row id which is part of its set
> of attributes. The row id is unique.
> 2) associates to each tuple an annotation that corresponds to the
> multiplicity of the tuple in the database. This annotation function
> corresponds to the function card in the definition of the semantics of
> SPARQL
>
>
> [1]
> http://www.w3.org/TR/2010/WD-rdb-direct-mapping-20101118/#rules_table_triples_no_pk
> [2]
> http://www.w3.org/TR/2010/WD-rdb-direct-mapping-20101118/#rules_literal_triples_no_pk
> [3]
> http://lists.w3.org/Archives/Public/public-rdb2rdf-wg/2011Jan/0044.html
>
>
>
>