RE: [xml-dev] Mixed content in data-binding (Was: Re: [xml-dev] Interesting pair of comments

["Andrew Layman" <andrewl@microsoft.com>]

Michael Kay wrote


> There are also applications of mixed content that don't fall into the 
> classic "marked-up text" model. For example, it can be used to record
> "properties of properties", as in

>
<email>fred@somewhere.com<last-modified>2005-02-02</last-modified></emai
l>

To make this fully supported by schemas, one would need a way to
indicate in schema rules for the cardinality, etc., of the "properties
of properties."

But there is also a versioning issue. Since adding such meta-data as the
last-modified date after the fact is a typical usage, attributes today
allow such annotation with less disruption to existing readers.  E.g. 

<email last-modified='2005-02-02'>fred@somewhere.com</email>

But this only works to one level.  One cannot add an attribute to that
attribute.

One could imagine a future version of XML that treated elements and
attributes with more parallelism, and allowed attributes to have
structure, perhaps with an element-like syntax, as in:

<email>fred@somewhere.com<@last-modified>2005-02-02</@last-modified></em
ail>

And

<email>fred@somewhere.com<@last-modified>2005-02-02<@says-who>Joe</@says
-who></@last-modified></email>