The processing of documentation, particularly with dexy, revolves around the idea of "filtering" documents. Processing documents can be complex, and although structured document forms can ease the burden. Processing documents by way of a series of filters, makes sense because a series of filters is easy to understand and is also simple to manipulate and extend as needs change.
There are a number of different approaches to processing and filtering documentation, and a lot of commentary on the subject. Dexy is a great example of this, but other resources and contributions to this discussion follow: