With thanks to a user in irc://irc.freenode.net/semanticmediawiki I have a workaround for this involving conditionally adding a category tag to top level pages in the User namespace as each new user page is created. With that category I no longer need a concept as described.

However, for future reference I'd be keen to learn if this problem is able to be solved with current query syntax.

---------- Forwarded message ----------
From: Na JeVi <najevi@gmail.com>
To: semediawiki-user@lists.sourceforge.net
Date: Thu, 30 Jul 2009 21:38:13 +1000
Subject: [Semediawiki-user] A concept that lists only the top level pages in a namespace
I want this concept to list only user names (preferably without the User: prefix) and definitely not list subpages within the User namespace. (It could be any namespace: Template: News: etc.)

Having studied 
 (i) http://semantic-mediawiki.org/wiki/Help:Concepts
and
 (ii) http://semantic-mediawiki.org/wiki/Help:Selecting_pages
I try:  

{{ #concept: [[User:+]] }}

However this concept also lists subpages within the User namespace.

So I tried these variations on the same theme:
[[User:+/]]
[[User:+!/]]
[[User:!+/]]
[[User:!/]]
[[User:+]] [[!/]]
[[User:+]] [[User:!+/]]
[[User:+]] [[User:!/]]
[[User:]]
[[User:~+/]]

Still no joy!

How might I modify this concept query to exclude any subpages in the target namespace?
I don't want to presume that all user pages:
 (a.) a have semantic data
or
 (b.) belong to a specific category

What page(s) can I read to learn more about this subject?