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Re: R2RML-based RDF mapping experiment in our Github repo

From: Ivan Herman <ivan@w3.org>
Date: Thu, 2 Oct 2014 18:26:01 +0200
Cc: W3C CSV on the Web Working Group <public-csv-wg@w3.org>, Anastasia Dimou <anastasia.dimou@ugent.be>
Message-Id: <E3AE96F8-A618-411D-80AF-AC5A276AC9D2@w3.org>
To: Dan Brickley <danbri@google.com>
Without having a clear idea of the details, but this mail triggered a possible strategy for further to make things more usable for the community:

1. We define the direct mapping with, possibly, a simple URI templating addition (embedded into the metadata). That would be the (minimal) Rec.

3. We may have 2-3 'extensions', ie, various languages that could be used for some use cases. Anastasia's RML/R2RML example is one, the mini-mustache that I worked on is another. We could/should
	- define hooks in the metadata to refer to those languages (and others) that an implementation may pick up. These references should also make clear that the referred engine should be used pre, post, or instead the direct mapping
	- we could publish, if we have the time and energy, WG Notes for those different languages, so that we could have some sort of a polished and stable reference to those.

Publishing as notes means that it is not considered as final, does not have, necessarily, a strong conformance, testing, etc, requirement, but it at least documents a possible approach. 


On 02 Oct 2014, at 17:44 , Dan Brickley <danbri@google.com> wrote:

> short version:
> R2RML-based mapping experiment here -
> https://github.com/w3c/csvw/blob/master/examples/tests/scenarios/moonwalkersdemo/
> longer version:
> With a lot of help from Anastasia Dimou (cc:'d) I've been looking
> again at an R2RML-based approach to RDF mappings and templates. See
> her mail back in February for an overview of the approach Anastasia
> and colleagues have been exploring:
> http://lists.w3.org/Archives/Public/public-csv-wg/2014Feb/0132.html
> Essentially they have taken W3C R2RML and generalized it to
> accommodate non-SQL input sources such as XML, JSON and ... CSV.
> "RML is defined as a superset of the W3C-standardized mapping
> language, R2RML, that maps data in relational databases to the RDF
> data model"
> They have a java implementation, "RMLProcessor" which can take a
> mapping file and generate an RDF graph as output. For now I have
> simply made a standalone version of an example that's bundled with
> that tool. The file "moon.sh" encapsulates all the configuration you
> need to run it on a unix or osx commandline. I've also copied sample
> output into the repo.
> Natural next steps would be to try this tooling with examples from our
> use cases (http://www.w3.org/TR/csvw-ucr/), many of which are in
> https://github.com/w3c/csvw/tree/gh-pages/examples/use-case-data-files
> Currently in this WG we have been more focussed on defining our direct
> mapping, and have looked also into super-simple mustache-based text
> templating with basic variable substititions. However I believe we
> also agreed recently that it should be possible to use our basic
> approach (JSON-LD metadata etc., column names etc.) in a way that
> describes how to apply more advanced templating mapping techniques.
> I'd like to use this RML/R2RML experiment to make sure that we can
> achieve this. If someone goes to the trouble to write RML/R2ML
> mappings from CSVs to RDF, we really should have a clear way to
> express that in W3C CSV metadata.
> Discussing this today with Anastasia we came back to a point that Phil
> Archer made yesterday on the call - which is that different parties
> should be able to write different mappings for different consuming
> applications. To follow through on that, perhaps a potential
> requirement is that our metadata should allow several templates to be
> given, each with inline information describing what they do.
> For example, a CSV of music events could have one mapping file that
> creates RDF for Google in schema.org (see
> https://support.google.com/webmasters/answer/4620133?hl=en), and
> another (with different target graph structures / vocabulary) for
> consumption by tools like
> http://simile-widgets.org/wiki/Reference_Documentation_for_Timeline
> But for now I'd be happy to have some more complete (R2RML/RML)
> mapping examples in our repo that work with CSVs from our use cases.
> If you can get RMLProcessor working, I believe the file moon.sh below
> should give you everything you need to get started.
> cheers,
> Dan
> Files:
> 1. https://github.com/w3c/csvw/blob/master/examples/tests/scenarios/moonwalkersdemo/museum-model.rml.ttl
> the mapping file.
> 2.
> https://github.com/w3c/csvw/blob/master/examples/tests/scenarios/moonwalkersdemo/moon-walkers.csv
> Simple CSV input.
> 3. https://github.com/w3c/csvw/blob/master/examples/tests/scenarios/moonwalkersdemo/_output.nt.txt
> The output (in N-Triples)
> 4.
> https://github.com/w3c/csvw/blob/master/examples/tests/scenarios/moonwalkersdemo/moon.sh
> Fiddly details :)
> This script is configured with the filetree path to the working
> folder, and can be run to generate RDF output given the above inputs.
> Background links:
> See http://rml.io/RML_R2RML.html for details, and http://rml.io/RML_R2RML.html
> http://rml.io/RML_publications.html
> http://events.linkeddata.org/ldow2014/papers/ldow2014_paper_01.pdf

Ivan Herman, W3C 
Digital Publishing Activity Lead
Home: http://www.w3.org/People/Ivan/
mobile: +31-641044153
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Received on Thursday, 2 October 2014 16:26:32 UTC

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