CruiseControl.NET:Configuration Preprocessor

Original Link:

Http://build.sharpdevelop.net/ccnet/doc/CCNET/Configuration%20Preprocessor.html

For example:

<cruisecontrol xmlns:cb= "Urn:ccnet.config.builder" >

<!--Included files (site-specific)--

<cb:include href= "config"/>

<cb:include href= "Email.xml"/>

<cb:include href= "Project.xml"/>

</cruisecontrol>

What does "cb:include" mean?

Is there any other similar definitions? How should I use them?

Take the above link for reference.