The YAZ CCL parser has extensive functionality beyond what is described here. For the full story, as well as a detailed description of the CCL language, please look at
http://www.indexdata.dk/yaz/doc/tools.tkl#CCL
The flexibility of the parser makes it easy, by setting up separate profiles for servers with different characteristics, to produce a client that performs different query mappings for different servers. Also, because you can configure operators, truncation characters, etc., in the CCL parser, it is simple to make it fit into almost any application.