This documentation was written to describe the 1.7.x series of Apache™ Subversion®. If you are running a different version of Subversion, you are strongly encouraged to visit http://www.svnbook.com/ and instead consult the version of this documentation appropriate for your version of Subversion.
Unlike CVS, a Subversion working copy is aware that it has checked out a module. That means if somebody changes the definition of a module (e.g., adds or removes components), a call to svn update will update the working copy appropriately, adding and removing components.
Subversion defines modules as a list of directories within a directory property; see the section called “Externals Definitions”.