Configuration is the task of taking existing vocabulary and constraint modules and combining them together to define a DITA document type.

You do configuration by creating new document type shells, which are DTD or XSD files that serve as manifests of the vocabulary modules that make up the DITA document types.

Configuration can also involve the creation of new constraint modules.

As an implementation activity, creating new document type shells is an entirely mechanical process that requires no knowledge of DTD or XSD syntax. The tutorials demonstrate the mechanical process. Likewise, because the process is entirely mechanical (meaning it requires no creative thought or invention), it can be automated, as it has been by Jarno Elovirta and his DITA DTD Generator (http://dita-generator.appspot.com/).

The development of constraint modules requires a bit more DTD or XSD knowledge, but it is also a largely mechanical process because it is always about removing or constraining existing things, not adding new things. Therefore, it does not require invention, only analysis of requirements and modification of existing declarations.