Re: The syntax issue

> 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

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

Received on Wednesday, 25 August 2010 12:52:45 UTC