I'm looking for the XSDs and documentation about META-INF/plexus/components.xml and META-INF/maven/lifecycles.xml which are used in Maven plugins.
The only documentation I've found so far is:
http://www.sonatype.com/books/mvnref-book/reference/writing-plugins-sect-plugins-lifecycle.html
Lifecycle XSD is at http://maven.apache.org/xsd/lifecycle-1.0.0.xsd (linked to from the documentation.)
Plexus is a project at Codehaus, I didn't see any documentation of their schema there (but I didn't dig too deeply).