The JNDI wrapper isCollection() method does something like:

if (resourcetype.equals("<collection/>")

to determine if a node is a collection or not. In my opinion
workspaces should be handled like collections by the SlideDirContext but
it would appear they are created differently, their resourcetype is
<D:collection xmlns:D="DAV:" />. Thus the SlideDirContext does not
treat them as a collection, with the result that workspaces are not browsable
as a SlideContext.