So the general areas of functionality of the new wftk (pretty much the same as the old wftk) are: data, actions, events, decisions, agents, workflow, notifications, and schedules. That doesn't match up all that well with the rough functionality outline taken from the chapter headings of the old book, but these are kind of the things that make up business processes.
The data organizer is a nice piece of functionality that breaks off conveniently, defining and naming data in terms of stores, indexes, and documents. My declarative language Decl is taking shape as a document-based language (its syntax and semantics are governed by the metadata of the document in question), and so it's becoming clear to me that a business action is also a document-based kind of thing, which can be expressed in Decl, use various resources, consume input documents, and create a result document (as enactment) and a series of attached output documents.
Events are essentially input queues. From a technical standpoint they're not terribly interesting, but events drive the machinery of a process. An event source pushes flow.
Which brings us to decisions.
A decision in a workflow context can be as simple as a logical test of variables, or as complex as an entire subprocess that involves not only calculation but even the execution of experiments that cost money and the input of human decision-makers. Decisions are arguably one of the most important aspects of a business. They need to be given careful thought.
There are a number of different ways to present decision structures, including simply as logical combinatorics, tables, and flowcharts, and they can be learned as decision trees (categorization is a generalization of decision - a non-binary decision, effectively).
I don't think they're going to rise to the level of being a separate module like the data organizer, but I think it's still valid to put decisions into a separate chapter of discourse, as it were.