RE: [xml-dev] RNG vs. XSD : is the use of abstract types andpolymorphis

[David Lee <dlee@calldei.com>]

Very interesting.  This also more clearly explains why RNG does not provide "type" like XSD does.
It provides validation but not typing.

I don't agree with the premise, however, that representing inheritance (or type) is irrelevant to the conceptual model. 
What if the conceptual model is in fact inheritance as opposed to a mechanism of representing a conceptual model.
It may be irrelevant to some classes of conceptual models ... 

----------------------------------------
David A. Lee
dlee@calldei.com
http://www.xmlsh.org

> -----Original Message-----
> From: Costello, Roger L. [mailto:costello@mitre.org]
> Sent: Monday, March 12, 2012 1:04 PM
> To: xml-dev@lists.xml.org
> Subject: RE: [xml-dev] RNG vs. XSD : is the use of abstract types and
> polymorphism a good or bad thing for schemas for XML?
> 
> John Cowan wrote:
> 
> > See http://www.thaiopensource.com/relaxng/design.html#section:15
> > for James's thinking on inheritance in schema languages.
> 
> Fascinating!
> 
> Here are a few excepts from the article:
> 
>     One of the most significant differences between RELAX NG and
>     W3C XML Schema is that RELAX NG does not have any concept
>     of inheritance.
> 
>     Inheritance has proven to be very useful in modeling languages
>     such as UML. However, I would argue that trying to make an XML
>     schema language also be a modeling language is not a good idea.
>     An XML schema language has to be concerned with syntactic details,
>     such as whether to use elements or attributes, which are irrelevant
>     to the conceptual model.
> 
>     ... there is no need for it to support inheritance; the role of the schema
>     language is purely to describe the XML syntax used to represent the
>     conceptual model.
> 
>     ... the role of the schema language is purely to describe the XML syntax
>     used to represent the conceptual model. RELAX NG has the advantage in
>     this role that it provides more flexibility in the choice of syntax.
> 
> /Roger
> 
> 
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