Metadata!

Metadata demystified: A guide for publishers
http://www.niso.org/standards/resources/metadata_demystified.pdf

A Framework of Guidance for Building Good Digital Collections
http://www.niso.org/framework/framework2.pdf

Understanding Metadata
http://www.org/standards/resources/understandingmetadata.pdf

Z39.50 - A Primer on the Protocol
http://www.niso.org/standards/resources/Z3950_primer.pdf

The Dublin Core Metadata Element Set
http://www.niso.org/standards/resources/Z39-50-2003.pdf

Information Retrieval (Z39.50): Application Service Definition and Protocol Specification ANSI/NISO Z39.50-2003 http://www.niso.org (sorry - forgot to record the full url!)