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   Re: [xml-dev] Media Types, Purposes, Natures, and XSL Transforms

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Eric Hanson wrote:

> Andreas Sewe (sewe@rbg.informatik.tu-darmstadt.de) wrote:
>>> Eric Hanson wrote:
>>>> The data in the two formats is pretty similar.  Typekit uses
>>>> nature and purpose as well.  It adds one more property,
>>>> mime-type, which indicates in the case of a transformation, what
>>>> the target mime-type of that transformation is.  This property
>>>> is optional however.
>> So, concerning media types, purposes and natures, can anybody explain  
>> to me
>> why Typekit, while using RDDL's notions of both nature and purpose to  
>> good
>> effect, differs in the way it describes a XSL transform? Compare the  
>> following
>> example from the Typekit Spec:
>> <tk:resource element="birdcall" src="display-birdcall.xsl">
>>   <tk:nature>http://www.w3.org/1999/XSL/Transform</tk:nature>
>> <tk:purpose>http://typekit.org/ns/typekit/0.2/purposes#display</tk: 
>> purpose>
>>   <tk:mimetype>application/xhtml+xml</tk:mimetype>
>> </tk:resource>
>> to
>> <rddl:resource
>>   xlink:href="display-birdcall.xsl"
>>   xlink:role="http://www.w3.org/1999/XSL/Transform";
>>   xlink:arcrole="http://www.w3.org/1999/xhtml";
>> />

Also see RDDL2 (Tim Bray's vocabulary): http://www.rddl.org/rddl2
>> Furthermore the semantics of RDDL's purpose differ from Typekit's  
>> purpose in
>> case of a transform. RDDL uses the purpose to indicate the result's  
>> type,
>> while Typekit indicates the result's purpose. IMHO such subtle  
>> semantic
>> differences should be avoided in case of two similar specs -  
>> especially since
>> they complement each other quite nicely.
> +1 for getting them the same.
> I'm not a big fan of how RDDL overloads nature/purpose to
> include info like this.  IMHO, nature should indicate what a
> resource *is*, purpose what it *does*, in general terms, without
> indicating any specifics.  Everything else should be external.

Fair enough. I was making the assumption that one can *infer* that  
something that *is* an XSLT *does* a transform but indeed it is  
overloading what would otherwise be a rddl:nature (of the result) with  
a rddl:purpose (i.e. that the purpose of a transform is to produce  
something with the nature of the result) If that makes any sense ...  
perhaps not.

I should point out that the way this is described in the RDDL spec is  
*explicitly* being used as an *example*.
RDDL 7.14: "
XSLT Stylesheet

An example of an XSLT stylesheet for RDDL, which accepts the params  
role and arcrole. The transform inserts the document referenced by  
xlink:href in the output. This code is shown as an example and is not  

I.e. the RDDL spec does not mandate that nature and purpose be used  
this way with XSLT, rather offers an example of how nature and purpose  
*might* be used with XSLT.



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