This post provides an overview of techniques you can use to handle conditional content in DITA. The need for complex conditions is a common reason organizations choose DITA as their content model. As conditional requirements get more complex, the basic Show/Hide functionality offered in many desktop publishing tools is no longer sufficient.
Conditional processing is especially interesting–or maybe problematic—when you combine it with reuse requirements. You identify a piece of content that could be reused except for one small bit that needs to be different in the two reuse scenarios.