xml-dev - Re: Structured attributes

["Bill la Forge" <b.laforge@jxml.com>]

Why not just extend the content model?

In addition to selection and sequence, we could have
'unique & unordered'.

Then we could deprecate attributes all together!
(To say nothing about having a far far richer content model.)

Bill

----- Original Message ----- 
From: Henry S. Thompson <ht@cogsci.ed.ac.uk>
To: XML Developers' list <xml-dev@xml.org>
Sent: Thursday, March 02, 2000 5:40 PM
Subject: Structured attributes


> [A moment's thought will lead to realisation that this is displacement 
> activity on the part of the XML Schema: Structures editor, who
> certainly has better things to do, but I need to get this off my
> chest.]
> 
> Why not structured attributes in XML?  _Why_ structured attributes?
> Well, we all know the comparison between elements and attributes as
> they stand:
> 
> Elements      Attributes
> ordered       unordered
> non-unique    unique
> structured    unstructured
> 
> There are a lot of contexts in which the first two properties of
> attributes are desireable, but the third is a serious constraint.
> 
> Here's a design sketch for adding structured attributes:
> 
>   1) Reserve a family of hitherto unusable names as the names of
>   structured attributes: On balnace I favour names with an initial
>   full-stop (.), but there are arguments in favour of using an initial
>   colon (:) instead;
> 
>   2) Use element syntax, at the beginning of all element content, with 
>      the following restrictions:
>      2a) No attributes on structured attributes;
>      2b) Contents is either all structured attributes or all text;
>      2c) Order doesn't matter;
>      2d) Uniqueness of names among sibling structured _and_, for children of
>          elements, vanilla old-style attributes.
> 
> Example:
> 
>   <person age='49'>
>    <.name>
>     <.first>Henry</.first>
>     <.last>Thompson</.last>
>     <.middle>Swift</.middle>
>   </.name>
>   <children otherParent='p33'>
>    . . .
>   </children>
>  </person>
> 
> The constraints above are equivalent to allowing 'attribute' children
> to the 'attribute' element in XML Schema, along with making the
> attribute name uniqueness constraint cumulative:
> 
>  <element name='person'>
>   <complexType>
>    <attribute name='age' type='integer'/>
>    <attribute name='name'>
>      <attribute name='first'/>
>      <attribute name='middle/>
>      <attribute name='last/>
>    </attribute>
>    <element name='children'>...</children>
>   </complexType>
>  </element>
> 
> Back to my day job :-)
> 
> ht
> -- 
>   Henry S. Thompson, HCRC Language Technology Group, University of Edinburgh
>           W3C Fellow 1999--2001, part-time member of W3C Team
>      2 Buccleuch Place, Edinburgh EH8 9LW, SCOTLAND -- (44) 131 650-4440
>     Fax: (44) 131 650-4587, e-mail: ht@cogsci.ed.ac.uk
>      URL: http://www.ltg.ed.ac.uk/~ht/
> 
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