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Re: "XML Schema specifies just syntax" versus "XML Schemaspeci

• From: Olivier Rossel <olivier.rossel@gmail.com>
• To: liam@w3.org
• Date: Thu, 10 Nov 2011 09:04:02 +0100

One weakness of XML Schemas is its difficulty to reuse, merge or
extend vocabularies.
Ex: if your semantic is about "food" and "airplanes", you will
probably never reuse any existing
XML schemas about "food" or "airplanes". You will have to reengineer your own.

One strength of RDFS is that a concept and relationships can be
defined at various
places, and the "system" will aggregate the definitions together.
So you can extend vocabularies easily (override is still an issue,
restriction is a very limited issue
because of open world assumption).

Another powerful capability of RDFS is to type (or untype!) instances
dynamically.
So a data is not stuck to a single role because of its original
definition or position in the data set.

The big advantage of XML is that it handles ordering of data, and
especially ordered lists, natively.
In RDFS, you have to explicitly define ordering of data, which is
sometimes cumbersome in an ontology/vocabulary.

For me, these technical points make it clear that RDFS is agile enough
to match the lifecycle of business vocabularies.
And XML Schemas is good at defining IT-processable data structures.



On Thu, Nov 10, 2011 at 5:24 AM, Liam R E Quin <liam@w3.org> wrote:
> On Wed, 2011-11-09 at 19:09 +0000, Costello, Roger L. wrote:
>> Hi Folks,
>>
>> Sally says, "XML Schema specifies just syntax."
>>
>> John says, "XML Schema specifies semantics."
>>
>> Who is correct?
>
> Neither.
>
> XML Schema Documents can define a grammar for a language that
> applications (including people) can imbue with meaning.
>
> The same is true for other syntaxes, such as RDF/Turtle, RDF/N3,
> RDF/XML.  The existence of the last of these is a proof that, if RDF can
> convey semantics, and if an RDF graph, once transmitted over RDF/XML,
> and reconstituted, still has the same semantics, RDF/XML can contain
> semantics, and therefore XML can contain semantics (and so can ASCII,
> and so can ethernet electrical signals...).
>
> Liam
>
> --
> Liam Quin - XML Activity Lead, W3C, http://www.w3.org/People/Quin/
>
>
>
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• References:
  • "XML Schema specifies just syntax" versus "XML Schema specifiessemantics"
    • From: "Costello, Roger L." <costello@mitre.org>
  • Re: "XML Schema specifies just syntax" versus "XMLSchema specifies semantics"
    • From: Liam R E Quin <liam@w3.org>