Can RDF be source?

[VladimirAlexiev]

@pmaria @DylanVanAssche @dachafra @andimou

https://github.com/kg-construct/rml-io/issues/42 talks about using CONSTRUCT as source, but the discussion has become muddied with considerations about other reference formulations, so I'd like to post this as a separate question.

AFAIK, so far RML hasn't been thought about as an RDF transformation tool (RDF to RDF) but as an RDFization tool (other formats to RDF).

So this idea is completely new to me.

IMHO the "best" RDF transformation tool is SPARQL

• CONSTRUCT to dump data while reformatting it
• UPDATE to reformat data inside a semantic database (a best practice is: INSEERT to another graph or repo)

(https://gist.github.com/VladimirAlexiev/cf2de89b692bbc2ae70917aae021ec07 includes some complex examples of such queries) Various RDFization tools take this approach:

• TARQL exposes each table row as variable bindings, then you use CONSTRUCT
• SPARQL Anything exposes data from CSV, JSON, XML, doc, html, zip etc etc to some raw RDF, then you use SPARQL to shape it the way you like

[andimou]

Hi @VladimirAlexiev

I think the idea of having RML to do RDF2RDF was there since a decade ago! 😄 Have a look here: https://doi.org/10.1145/2814864.2814873

If it's a good idea or not, that's a different discussion. Back then we did it mostly to reuse URI identifier which already existed in other RDF graphs.

[DylanVanAssche]

From #55

If we allow RDF terms for Source, we also need to define NULL values with rml:null for resources based on RDF and SPARQL?