Re: R2RML Linked Data Aspects

On Mar 14, 2011, at 23:35 , Sören Auer wrote:

> Am 14.03.2011 18:55, schrieb Ivan Herman:
>>> 2. *namespaces* - I could not find any possibility to declare namespaces
>>> and respective prefixes in the current draft. is that left out
>>> intentionally? If not, we should add a respective declaration and make
>>> clear, that only namespaces which are governed by the user creating the
>>> mapping can be made de-referencable later on for Linked Data publishing.
>>> 
>> 
>> I just want to understand: do you mean namespaces to be used within an R2RML file or namespaces and prefixes in the generated file?
>> 
>> I am not sure I understand the need for the former; I suspect this is not what you meant.
>> 
>> As for the latter: my understanding is that R2RML defines a way to generate RDF triples from tables. I mean: RDF triples in the abstract, conceptual sense, and not in any particular serialization. On the other hand, the usage of prefixes/namespaces is a matter of a particular serialization; I am not sure it has a place in R2RML...
> 
> In some literal values of R2RML properties (such as e.g. rr:SQLQuery)
> (as well as inside some tables) it would make sense to use CURIE-like
> identifiers. Currently it looks like it is left unclear, wether this is
> possible and what namespaces will be used. From my point of view we need
> at least two distinguished default namespaces - one for schema elements
> (i.e. classen and properties) which are generated by R2RML and one for
> the actual data.

Well, that is what I am questioning, in fact. *RDF* does not have a concept of namespaces, only serializations do. And the different serializations (RDF/XML, Turtle, RDFa, soon JSON) may have different approaches. R2RML does not define which serialization is used at the end of the process...

Ivan


> In addition it should be possible to define and use
> more namespace prefixes.
> 
> Maybe also I got something wrong. ;-)
> 
> Sören
> 


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Ivan Herman, W3C Semantic Web Activity Lead
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