Re: [xml-dev] DTDs don't have ID or IDREF elements so why does XMLSchema

[Peter Flynn <peter@silmaril.ie>]

On 01/03/2022 23:52, Michael Kay wrote:
> Orthogonality, or to put it another way, avoiding arbitrary 
> restrictions. If ID and IDREF are going to be among your set of data 
> types, then why would you want to disallow people from using them on 
> elements.
It's part of the way some people view XML. I struggle to find any use 
case for using ID or IDREF on elements. In fact, I would argue that 
adding an ID or IDREF attribute to an element type *is* "using it on 
elements".

> (Personally, I would have made "IDness" and "IDREFness" properties 
> that are orthogonal to type. I can't see any good reason for
> disallowing IDs of type integer or date.
If we accept IDs must be unique within the document, I have encountered 
many reasons, such as "integers" that aren't (ie leading zeroes), and 
dates that turn out later to need multiple occurrences.

> But the SGML and DTD legacy weighed strongly on the XSD designers.)
I am very glad they did.

Peter

> > On 1 Mar 2022, at 23:32, Roger L Costello <costello@mitre.org> wrote:
> >
> > Hi Folks,
> >
> > DTD only allows attributes to be of type ID and IDREF.
> >
> > XML Schema allows both attributes and elements to be of type ID and IDREF. Why? Is there a compelling use case for declaring an element to be of type ID? Is there a compelling use case for declaring an element to be of type IDREF?
> >
> > /Roger
> >
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--
Peter Flynn
Cork 🇮🇪 Ireland 🇪🇺