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

From: Steven Ericsson-Zenith <steven@semeiosis.org>
Date: Wed, 9 Nov 2011 11:21:29 -0800
Cc: "xmlschema-dev@w3.org" <xmlschema-dev@w3.org>
Message-Id: <A3298A38-5323-43D5-82C1-477AE9370CD1@semeiosis.org>
To: "Costello, Roger L." <costello@mitre.org>
In Logic "semantics" refers to the rules of valid syntax and its transformation. I can't make any sense of the definition given here.

With respect,
Steven


On Nov 9, 2011, at 11:10 AM, Costello, Roger L. wrote:

> Hi Folks,
> 
> Sally says, "XML Schema specifies just syntax."
> 
> John says, "XML Schema specifies semantics."
> 
> Who is correct?
> 
> First, we need to be clear on what is meant by "semantics."
> 
> I will define it as such: 
> 
>    The semantics of a thing is its relationships to other things
>    and its properties. 
> 
> In this discussion I focus exclusively on "relationships." 
> 
> Here are examples of expressing relationships:
> 
>    - Book is an Object.
>    - Person is an Object.
>    - author is a property.
>    - title is a property.
>    - name is a property.
> 
> The examples show a "kind-of" relationship between Book/Person to Object, and author/title/name to property.
> 
> "kind-of" is only one type of relationship. There are many others, such as "same-as."
> 
> So the question resolves, at least in part, to this:
> 
>      Does XML Schema allow relationships to be expressed?
> 
> With XML Schema you have the ability to create a complexType and then do derive-by-restriction or derive-by-extension on it.  For example, you may create a Book complexType that extends a Publishing complexType. Isn't that an example of XML Schemas expressing a relationship? If yes, then isn't it demonstrating that "XML Schema specifies semantics"?
> 
> No, not really.
> 
> The derive-by-extension and derive-by-restriction capability specifies a complexType by reusing another complexType. That is quite a different thing from expressing a relationship for the purpose of informing.
> 
> Here's what Michael Kay said regarding the use of derive-by-restriction and derive-by-extension to specify semantics:
> 
>    I think it's probably a mistake to try and use the concept 
>    of 'type' to represent an ontological distinction ...
> 
> Even if we grant that derive-by-restriction and derive-by-extension specifies a legitimate ontological relationship, it can only specify one type of relationship (namely, subclass). Typically, a much more varied set of relationships is needed to fully inform.
> 
> Here's what Eliot Kimber said:
> 
>    There is no sense in which they [XML Schemas] can be 
>     anything more than a very weak reflection of some deeper 
>    ontology.
> 
> Conclusion: XML Schemas specifies syntax only.
> 
> What do you think?
> 
> /Roger
Received on Thursday, 10 November 2011 14:41:27 GMT

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