xml-dev - Re: Schema concepts

["Wang,David" <dwang@mitre.org>]

Very simple.  Terseness is not a design goal. :-)

I am no authority on this, but this is my understanding:
OOP classes binds "elements and types" together as one (implicitly), whereas
in XML Schema they are actually separated, so all elements have to have a
type or datatype.  Thus, you'd have to build up a type-hierarchy alongside
an element one, depending on how you want to use it.

> Hello!
>
> I was asked to give an example why I consider
> the current XML schema syntax too complicated.
>
> So, suppose I want to describe pictures built of
> circles, lines and rectangles.
>
> The first example is how I would expect
> schema coding if I am used to OOP:
>
>   <element name="pictureElement" abstract="true">...</element>
>
>   <element name="picture">
>     <element minOccurs="0" maxOccurs="*" ref="pictureElement"/>
>   </element>
>
>   <element name="circle" source="pictureElement"/>...</element>
>
>   <element name="line" source="pictureElement"/>...</element>
>
> The second example is what I really
> need to do using the current XML Schema draft:
>
>   <type name="pictureElement">...</type>
>
>   <element name="pictureElement" type="pictureElement"/>
>
>   <element name="picture">
>     <type>
>       <element minOccurs="0" maxOccurs="*" ref="pictureElement"/>
>     </type>
>   </element>
>
>
>   <type name="circle" source="pictureElement">...</type>
>
>   <element name="circle" type="circle" equivClass="pictureElement"/>
>
>   <type name="line" source="pictureElement">...</type>
>
>   <element name="line" type="line" equivClass="pictureElement"/>
>
>
> The circle and line elements cannot just have
> annonymous types since I may want to reuse
> their structure.
>
> Now, my question is: Is anyone able to generate
> a counter-example that justifies the
> current schema overhead?