The semantics of a specification in a library is a function of a global environment that maps names of specifications (previously declared or downloaded in the same library) to their denotations. The global environment at the end of the library gives the semantics of the entire library.
A directory of registered libraries maps library names to their registered URLs. Since the names include version numbers, this directory also gives access to previous versions of libraries.
Finally, the semantics of the whole collection of CASL libraries depends on the current state of the Internet, associating URLs to the contents of particular libraries.