Re: [xml-dev] abstract types

[ht@cogsci.ed.ac.uk (Henry S. Thompson)]

"Maciejewski, Thomas" <Thomas.Maciejewski@lehman.com> writes:

> Is there a way to enforce abstract types.  For example lets say I have an
> interface : printable  
> 
> but then I have a concrete "class" wordDocument that derives from printable
> with some additional information.  Lets say I would like to serialize these
> objects to XML.  Lets say I also have a class queue that can have many
> "printable" objects ... 
> 
> so in my xml I would like to have :
> 
> <foo>
> 	<wordDocument name="toms document" />
> 	<excelDocument name="toms spreadsheet" />
> </foo>
> 
> but not allow:
> <foo>
> 	<printable />
> </foo>

There are serveral ways to do this.  Most straightforward is

1) Declare printable as an abstract element at the top-level with a
type which covers all the possibilities for your concrete classes;

2) Declare foo to have printable* as its content;

3) Declare wordDocument and excelDocument at the top level with
substitutionGroup='printable' and types derived from the type of
printable.

You're done.

ht
-- 
  Henry S. Thompson, HCRC Language Technology Group, University of Edinburgh
          W3C Fellow 1999--2002, part-time member of W3C Team
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