RE: [xml-dev] Xlink Isn't Dead

["Michael Kay" <mike@saxonica.com>]

> 
>          What's an example of a non-hierarchic relationship 
> as it applies to links?

The relationship of an author to a publisher.
> 
> > >* independence of document boundaries
> 
>          In what sense? Again, an example would be good.

A link from the text of a chapter to a bibliography entry should be much the
same whether the bib. entry is in the same XML document as the chapter or in
a different document.
> 
> > >* indirection between identifiers of objects and the 
> addresses of the 
> > >documents containing them
> 
>          Examples and elaborations would be helpful.

An ISBN is clearly an identifier, not a pointer. An HTML @href attribute is
clearly a pointer, not an identifier. We need to use identifiers in
conjuction with a mechanism than can enable us to locate the things they
identify, but without "hard coding" the pointers in places where we should
use identifiers. The attempt to make URIs serve as both identifiers and as
pointers seems to be an unmitigated disaster.
> 
> > >* indirection between identifiers of objects and their XML 
> > >representations

We shouldn't confuse a reference to a person with a reference to their home
page on the web. Obvious, but I've read a lot of stuff in the "semantic web"
space that appears to encourage this confusion: again, by trying to overload
URIs to serve both purposes.
> 
> > >* flexibility in the management of referential integrity
> 
In a document containing information about an employee, there's probably a
reference to their manager. That needs to be a valid reference to a current
employee of the company. In a press release issued by the company, there's
probably a reference to the person who issued it. That can be an
ex-employee. We need to be able to say declaratively what should happen to
references when the objects they refer to change or disappear.
> 
> > >* versioning
> 
>          On the wrong side of the 80/20, in my opinion.

People often put versioning on the wrong side of the 80/20, and that
accounts for a lot of our problems. The biggest problem with relationships
is managing change (the "broken links" problem). You can't put that problem
to one side and hope it goes away.

Michael Kay