Re: The syntax issue

* Michael Hausenblas <michael.hausenblas@deri.org> [2010-08-25 13:52+0100]
> 
> > I propose to proceed based on the concepts of Souri's approach, but
> > with an RDF serialization instead of XML as the surface syntax.
> 
> +1

given the community of use, I also see RDF as more practical than XML.

> Cheers,
>       Michael
> 
> -- 
> Dr. Michael Hausenblas
> LiDRC - Linked Data Research Centre
> DERI - Digital Enterprise Research Institute
> NUIG - National University of Ireland, Galway
> Ireland, Europe
> Tel. +353 91 495730
> http://linkeddata.deri.ie/
> http://sw-app.org/about.html
> 
> 
> 
> > From: Richard Cyganiak <richard@cyganiak.de>
> > Date: Wed, 25 Aug 2010 12:42:13 +0100
> > To: RDB2RDF WG <public-rdb2rdf-wg@w3.org>
> > Subject: The syntax issue
> > Resent-From: RDB2RDF WG <public-rdb2rdf-wg@w3.org>
> > Resent-Date: Wed, 25 Aug 2010 11:42:50 +0000
> > 
> > Harry correctly urges us to press forward with turning the SQL-Based
> > Approach into a FPWD.
> > 
> > There is one major obstacle though that needs to be tackled before
> > work on a FPWD can be started: the question what syntax the language
> > should use.
> > 
> > Ashok has stated that we should talk about syntax ³later², but this
> > discussion has to happen before serious work on an official draft
> > starts. Once a draft is out, the public will assume that the syntax
> > used in the draft is the official and canonical syntax for the
> > language, and it is key to send the right signal there.
> > 
> > Which means, the discussion has to happen now.
> > 
> > 
> > I can understand Souri's decision to base his initial work on XML. But
> > I believe that XML is not the best choice of syntax for R2RML. I
> > instead propose that R2RML mappings should themselves be RDF graphs,
> > with Turtle or RDF/XML as the default syntax for writing R2RML files.
> > 
> > Here is why.
> > 
> > 
> > 1. CHARTER REQUIREMENTS
> > 
> > The RDB2RDF charter states: ³The mapping language SHOULD have a human-
> > readable syntax as well as XML and RDF representations of the syntax
> > for purposes of discovery and machine generation.² [1] Using RDF kills
> > three birds with one stone: It ticks the RDF box, it ticks the ³human-
> > readable syntax² box (Turtle), and it ticks the XML box (RDF/XML).
> > 
> > 
> > 2. PREFIX HANDLING
> > 
> > The language needs to refer to RDF vocabulary terms, which are
> > identified by URIs, and are conventionally represented as QNames or
> > CURIEs (that is, http://xmlns.com/foaf/0.1/Person is represented as
> > foaf:Person). This means that the language needs features for
> > establishing prefix mappings (associate "foaf" with
> > "http://xmlns.com/foaf/0.1/
> > "). This is a source of pain in XML-based languages (cf. ongoing
> > tensions over RDFa vs HTML5, and RIF's XML syntax). Using a language
> > that has a built-in mechanism for establishing prefix mappings and
> > expanding QNames/CURIEs would avoid this problem.
> > 
> > 
> > 3. EXTENSIBILITY
> > 
> > RDF gives us various ways of annotating mappings (e.g., providing
> > additional documentation, versioning-related annotations, cross-links
> > to other software artifacts etc) for free. For example, I could attack
> > rdfs:comment, dc:modified, dc:creator and similar properties to any
> > part of a mapping. It also provides a clear syntactical framework for
> > vendor-specific extensions.
> > 
> > 
> > 4. COMMUNITY EXPECTATIONS
> > 
> > R2RML is a language for mapping databases to RDF. Hence, it bridges a
> > world that speaks SQL to a world that speaks the RDF technology stack
> > (RDF, SPARQL, RIF etc). Hence, arguments can be made for basing R2RML
> > syntax on RDF (like in D2RQ or SquirrelRDF), or on SQL (like Virtuoso
> > RDF Views), or on SPARQL (like Eric's approach), or on RIF. Basing
> > R2RML on XML drags an unrelated third technology stack into the mix.
> > 
> > 
> > 5. SUITABILITY OF XML FOR CONFIGURATION
> > 
> > XML is a good syntax for text markup (cf. XHTML, DocBook, TEI). It
> > works ok for transmitting structured data (cf. SOAP, Atom) albeit
> > facing increasing competition from JSON. But I think it is now evident
> > that using XML for configuration files that are edited and read
> > directly by users is not a good idea. The most obvious drawback in
> > this context is that you have to type everything <twice>...</twice>!
> > 
> > 
> > 
> > To show what Souri's approach could look like if rendered in RDF
> > (specifically Turtle), I took his example [2] and re-wrote it in
> > Turtle [3] syntax. You can find it here:
> > 
> > http://www.w3.org/2001/sw/rdb2rdf/wiki/R2RML_in_Turtle
> > 
> > A raw version of just the file [4] and auto-generated graph view [5]
> > are also available.
> > 
> > I propose to proceed based on the concepts of Souri's approach, but
> > with an RDF serialization instead of XML as the surface syntax.
> > 
> > Opinions?
> > 
> > Best,
> > Richard
> > 
> > 
> > [1] http://www.w3.org/2009/08/rdb2rdf-charter.html
> > [2] 
> > http://www.w3.org/2001/sw/rdb2rdf/wiki/Example_of_SQL-based_RDB2RDF_Mapping:_R
> > evision_1
> > [3] http://www.w3.org/TeamSubmission/turtle/
> > [4] http://github.com/cygri/r2rml/raw/master/examples/emp-dept.ttl
> > [5] http://bit.ly/asIik4
> 
> 

-- 
-ericP

Received on Wednesday, 25 August 2010 13:33:53 UTC