Clients retrieve calendar data by submitting requests using the HTTP protocol layer. This is a minimal HTTP server implementation, streamlined to support calendar requests. This is done by appending Web Calendar Access Protocol (WCAP) commands to the URL.
WCAP is an open protocol that allows you to write your own interface to Calendar Server. Using WCAP commands (.wcap extension), you can perform most server commands, except for certain administrative commands. You can use WCAP commands to request output as XML or iCalendar wrapped in HTML.
For information about WCAP commands, see the Sun Java System Calendar Server 6.3 WCAP Developer’s Guide.