POWDER primer

In discussions of metadata discovery, the W3C POWDER project is mentioned
frequently. It has a different design center than XRD, i.e., it is not
intended primarily for resource discovery. But it is still helpful to
understand what it is and how it works. I found the POWDER Primer very
helpful in providing an overview:

	http://www.w3.org/TR/2008/WD-powder-primer-20080815/

=Drummond