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Re: Blank nodes as subject maps in R2RML

From: Tomasz Pluskiewicz <tomasz.pluskiewicz@gmail.com>
Date: Wed, 25 Jul 2012 16:05:12 +0200
Message-ID: <CAAFOhSfWw4sv8MvYogWZ2O0FUYnJN10yB+9oBkJpHbh9Z8wn5g@mail.gmail.com>
To: Juan Sequeda <juanfederico@gmail.com>
Cc: David McNeil <dmcneil@revelytix.com>, public-rdb2rdf-comments@w3.org
Hello again.

Sorry to revive an old topic, but I have recenlty realized the root of
my question.

The R2RML specs at http://www.w3.org/TR/r2rml/#dfn-term-map state
clearly that "A term map must be exactly one of the following: a
constant-valued term map, a column-valued term map, a template-valued
term map." Doesn't this mean that a term map

<StudentsTriplesMap> rr:subjectMap
[
    rr:termType rr:BlankNode;
    rr:class <http://example.com/Student>
];

is in fact invalid, having no explicit rr:constant, rr:column or
rr:template property?

Regards,
Tomasz

On Fri, Jun 8, 2012 at 10:19 PM, Tomasz Pluskiewicz
<tomasz.pluskiewicz@gmail.com> wrote:
> Thank you for answering. Also, let me answer here again.
>
> I forgot to mention I intended the mapping as default mapping for
> table without primary key.
>
> In my oppinion by default direct mapping should generate a blank node
> for each row. And I do have mixed feelings about the behavior not
> preserving duplicate rows.
>
> Regards,
> Tomasz
>
> On Fri, Jun 8, 2012 at 6:26 PM, Juan Sequeda <juanfederico@gmail.com> wrote:
>> I asked on the forum, but let me ask here.
>>
>> are you expecting the R2RML engine to generate a blank node for each tuple,
>> or do you have a column value that you would like to use in order to
>> generate the blank node?
>>
>> Juan Sequeda
>> +1-575-SEQ-UEDA
>> www.juansequeda.com
>>
>>
>>
>> On Fri, Jun 8, 2012 at 9:22 AM, David McNeil <dmcneil@revelytix.com> wrote:
>>>
>>> >From the latest R2RML draft:
>>>
>>> * a subject map is a term map,
>>> http://www.w3.org/2001/sw/rdb2rdf/r2rml/#dfn-term-map
>>>
>>> * the termType property can be used on term maps,
>>> http://www.w3.org/2001/sw/rdb2rdf/r2rml/#termtype
>>>
>>> So "yes", you can use termType on subject maps and this is how you would
>>> produce subjects as blank nodes.
>>>
>>> -David
>>
>>
Received on Wednesday, 25 July 2012 14:06:30 UTC

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