Non-standard metadata in Aperture web templates?

<p>I'm considering moving from Expressions Media (aka iView Media Pro) to Aperture, but Expressions has a necessary feature I can't find in any discussion or documentation about Aperture: the ability to define custom metadata and then use it in a web page template.<br>

For example, I have web pages (photos of artwork) that are tagged with things like medium (e.g oil, pastel), size, year created, etc. My Expressions templates (all hand-created) refer to these metadata tags to display the information on the pages.<br>

Aperture's web templates appear to use a similar metadata reference, but I can't see any mention of referring to *custom* metadata tags. Any ideas?</p>