DublinCore
DublinCore Resources
The DublinCore is "A metadata format defined on the basis of international consensus which has defined a minimal information resource description, generally for use in a WWW environment." "Dublin Core metadata is specifically intended to support resource discovery. The elements represent a broad, interdisciplinary consensus about the core set of elements that are likely to be widely useful to support resource discovery."
The PTK/CMF uses the DublinCore for standard classification of the objects.
Dublin Core Metadata Element Set (DCES): http://purl.org/dc/
Elements of the DCES v1.1: http://www.purl.org/dc/documents/rec-dces-19990702.htm
Qualifiers of the DCES v1.1: http://www.purl.org/dc/documents/rec-dces-19990702.htm
Chris Petrilli's Standard Metadata proposal: http://www.zope.org//Wikis/DevSite/Proposals/StandardMetadata