Content definitions offer another mechanism for extending the content types that OpenCms will support. Unlike resource types, which merely create a new type of document within the existing OpenCms architecture, a content definition allows you to create a complex, external content control mechanism that does not use the predetermined facilities of resource types. Phrased more simply, content definitions provide a way of storing data that is fundamentally different from existing OpenCms data, but controlling it through the OpenCms back office and publishing system.

The OpenCms developers created a News module (that has since been extended by a number of independent developers), which made use of content definitions to create a completely different type of content. This content is stored in non-OpenCms tables in the database, accessed by a separate pool of database connections, and managed by a custom set of back office classes.

Content definitions are not designed to integrate...