In addition to entries for individual catalogues, configuration files can also contain entries for other configuration files. Typically when such an entry is chosen all the entries in the target configuration file are loaded into the client. In this way a tree (or rather a network, because recursion is allowed) of entries can be built up. Entries of this type are referred to as `directories' (by analogy with an hierachical file system).
For a directory entry the serv_type should be `directory' and the url should be the URL of the destination configuration file. long_name and short_name have their usual meaning. Other options are unlikely to be required. An example might be:
serv_type: directory long_name: ESO Catalogues short_name: catalogs@eso url: http://archive.eso.org/skycat/skycat2.0.cfg
Writing Catalogue and Image Servers for GAIA and CURSA