requirements for XML Schema 1.1

I am writing to propose two requirements

1. A removal of the constraint that requires elements with the same name
to have the same type.
2. A concrete syntax for XML Schema.

 

One problem with XML Schema is the constraint that if two elements with
same name are in the same set of particles of a model group, then the
elements have the same type. The problem with this constraint is that
you cannot ensure that different occurrences have different structures.
Suppose you want an XML schema that has the following as an instance
document.

 

<?xml version="1.0" encoding="UTF-8"?> 
<semicolon>

<b><x/><y/></b>
<b><g/></b>

</semicolon>

 

However, you did not want the following as an instance document.

<?xml version="1.0" encoding="UTF-8"?>

<semicolon>

<b><g/></b>

<b><x/><y/></b>
</semicolon> 

 

If I understand the semantics of XML Schema correctly, you cannot define
a model group that only allows the first to be an instance document, but
not the second.

However, I can define a context free grammar that would accept the first
and reject the second. 

 

A -> B semicolon B'

B -> b(x, y)

B' -> b (g)

 

 

Concrete Syntax for XML Schema

------------------------------------------------

It would be much easier to develop XML Schema if there was a concrete
syntax for XML Schema. XML Schema 1.1 should also include a concrete
syntax. Vendors can develop translators from the concrete syntax to raw
XML Schema.