BUG: use="required" not enforced for global attributes

[Ramesh Gupta <ra...@eNode.com>]

In the following schema [1], element 'foo' is required to have two
attributes -- 'bar' and 'baz'.

The following instance [2] validates successfully with Xerces 1.2.3.

If you remove the 'baz' attribute from the instance, Xerces will correctly
report that the attribute is required.

However, if you remove the 'foo:bar' attribute from the instance, Xerces
will still validate it successfully even though it is a required attribute.

Ramesh

[1] Schema
==========
<?xml version="1.0" encoding="UTF-8"?>
<schema xmlns="http://www.w3.org/1999/XMLSchema"
        targetNamespace="FooNamespace"
        xmlns:foo="FooNamespace"
        xmlns:xsi="http://www.w3.org/1999/XMLSchema-instance"
        xsi:schemaLocation="http://www.w3.org/1999/XMLSchema
http://www.w3.org/1999/XMLSchema.xsd">

    <import    namespace="http://www.w3.org/XML/1998/namespace"
            schemaLocation="http://www.w3.org/2000/04/xml.xsd"/>

    <element    name="foo" type="foo:FooType"/>
    <attribute  name="bar" type="string"/>
    
    <complexType name="FooType" content="empty">
        <attribute ref="foo:bar" use="required"/>
        <attribute name="baz" type="string" use="required"/>
    </complexType>

</schema>

[2] Instance document
=====================
<?xml version="1.0" encoding="UTF-8"?>
<foo xmlns="FooNamespace"
     xmlns:foo="FooNamespace"
     xmlns:xsi="http://www.w3.org/1999/XMLSchema-instance"
     xsi:schemaLocation="FooNamespace http://localhost/fooSchema.xsd"
     foo:bar="here" baz="here"/>