[w3c sml] Revised proposal for 4774 schema binding

Link to the issue: http://www.w3.org/Bugs/Public/show_bug.cgi?id=4774

I've made some minor changes to the proposal we submitted earlier in the 
following email. Changes since V2 are highlighted.

http://lists.w3.org/Archives/Public/public-sml/2007Oct/0058.html

The only change is to add a <defaultSchema> element under <schemaBindings> 
to make it easy to specify a default schema that's used to validate 
instance documents not explicitly covered by any <schemaBinding>.

In the interest of getting consensus on this issue, I suggest we make it 
optional for processors to support <schemaBindings>.

To summarize the key points of this proposal:
1 Add a new element <schemaBindings> (parallel to <ruleBindings> we 
already have)
2 <schemaBindings> can have any number of <schemaBinding> children, each 
specifies a schema that's used to validate instance documents listed 
inside this <schemaBinding>. We can use the same "prefix matching" 
mechanism as <ruleBindings>.
3 <schemaBindings> can have an optional <defaultSchema> child, to specify 
the schema used to validate all instance documents not covered any 
<schemaBinding>.
4 If a <defaultSchema> is not present, then a schema is composed from 
*all* schema documents and used to validate instances not covered by any 
<schemaBinding>.
5 Processors are not required to support <schemaBindings> (that is, they 
are allowed to always compose a schema from all schema documents and use 
it to validate all instance documents)
6 schemaLocation on <include> and <redefined> are resolved using aliases
7 xsi:schemaLocation attributes and schemaLocation on <import> elements 
are ignored

Hope I didn't miss anything important. The exact syntax can be fine-tuned.

Thanks,
Sandy Gao
XML Technologies, IBM Canada
Editor, W3C XML Schema WG
Member, W3C SML WG
(1-905) 413-3255 T/L 313-3255