A name test without a prefix only matches something without a namespace.

For example:

m:section/title

matches

<m:section xmlns:m='urn:...'>
<title>No Namespace</title>
</m:section>

but not

<m:section xmlns:m='urn:...' xmlns='urn:something-else...'>
<title>I've got a namespace</title>
</m:section>

Remember, name matching is based on local name and namespace name alone!!!