The framework uses the Apache XML commons resolver to avoid
accessing the Internet for Catalog files. The resolver is configured
through the CatalogManager.properties
and
xml-catalog.xml
files in the
src/resolver
directory of the distribution.
If you update e.g. the Docbook XML version, you must also update the catalog file to match the new version. Else the rendering process will have no knowledge of your changes and access the Internet to download the required DTD files.