The identifier systems used by the SGML and by some tools are based on catalogues which perform the translation of these identifiers over to files holding the necessary definitions.
The section on tailoring a catalogue (see Section 4) will give more details about these files.
For such tools to be able to find the necessary catalogue(s) the value of the environment variable SGML_CATALOG_FILES should be configured, as shown in the following example:
This is the only necessary additional configuration for the DocBook, tools and the like to work correctly on your platform.