The RdfCalendar schema used to be generated from selected icalendar test files. It's not any more. It's generated from the RFC; see ical RDF schema: derived from the RFC, OWL-DL happy, has versionInfo Mar 2004 to rdf-calendar.
Pourquoi n'y a t-il pas plus d'information ? I don't know much french, but if you're asking why the old info was removed, it's still there in the change history.