XML Default namespaces for unqualified attribute names?

Question

I'm trying to understand the correct interpretation of the "Namespaces in XML 1.0 (Third Edition)" definition for unqualified attribute namespaces.

"The namespace name for an unprefixed attribute name always has no value."

And later in the same section:

"The attribute value in a default namespace declaration MAY be empty. This has the same effect, within the scope of the declaration, of there being no default namespace."

So if I want to declare a default namespace for an element (and its children), do I also have to declare a prefix-namespace mapping for any attributes which reside within that namespace?

For example, in this example

<parent xmlns="http://example.com/foo"&gt;
    <child attrib="value">text</child>
<parent>

I would interpret the above definition to say that the namespace of attrib is empty.

So if I needed attrib to have the same namespace as parent, then I would be forced to do this?

<foo:parent xmlns:foo="http://example.com/foo"&gt;
    <foo:child foo:attrib="value">text</foo:child>
<foo:parent>

or this?

<parent xmlns="http://example.com/foo" xmlns:foo="http://example.com/foo"&gt;
    <child foo:attrib="value">text</child>
<parent>

This seems silly to me as it appears to defeat the purpose of default namespaces. I'm hoping that I'm just misunderstanding the spec.

Answer 1

Your interpretation of the spec is correct. Some kind of rationale is also given in the second paragraph of section 6.2 in the namespaces spec you referenced:

the interpretation of unprefixed attributes is determined by the element on which they appear.

But I would also be interested in some more details on why this specific behavior was chosen.