Thursday, April 19, 2007

Workflow systems

I'm looking at workflow systems for work and I'm very much enjoying it so far. The main package I'm looking at is called "jBPM". It's quite a large package to understand.

Workflow programming, to begin with, is different from actual programming in that it focuses on the process and on the execution of things, not on appearance or transformation of data. What I quite enjoy is that this statement means that you focus on the middle part of the construction of a system, rather than focus on the beginning (screens, user input) or the very end (database) or how some requirement fits in with your current system in an architectural way.

So, in order to successfully construct workflow-based systems, you first need to change your thinking about IT and how systems get constructed. It's not necessarily a very (pedantically) 'clean' way of programming (all data is stored in proper elements and there is compile-time dependency between all objects and all that), but it provides much more decoupling between functions, which on thus on the other hand improves reusability and componentization.

You should think of workflow as a series of automatic or manual actions that need to take place, easy to re-arrange and reusable. These actions are arranged in a diagram, which specifies which actor or pool of actors can execute those actions. The final part of the diagram also states whether these actions are executed in parallel or in series. To top things off... the whole process "instance", that particular order or that particular holiday request will get persisted into a database when it has no way to proceed immediately because it is waiting for external actions. You do not get these features "automatically" from any software language.

The latter word "language" is specifically mentioned, because you will start to mix your domain language (say Java or C#) with another "graph-based" language, in this case XML. So, the XML specifies authentication, actors, pools, the "flow" of the process, whereas the domain-based language helps to express componentized functionality (such as performing a credit-check, updating databases, gathering user input and so forth).

If you re-read the last paragraph, you notice how different workflow-based programming essentially is and how it could provide enormous value to IT systems if it is done right.

As an example, if you know Mantis or BugZilla, you know from the developer's or tester's point of view what the screen looks like for bug manipulation. Well, this screen is a single screen with all components in editable form, but from a workflow point of view, it should be constructed differently every time with only those components required for that particular step... For example, if you start to update or categorize the bug, then you do not need all the fields available in the screen to do that. When you have a process that dictates the need for a CCB comment, then you also have far too many elements on your screen to do specifically just that.

The point is that in general, many applications show everything on screen that you may not necessarily care about at that time and the user needs to compensate for the lack of guidance by understanding the process documented elsewhere in a very large document... Wouldn't it be great if we could just look at a screen and get our business process right and know what to do at the same time?

The other thing I notice is that many SRS documents are not necessarily focused on the process, but are focused on data. This shows me that there must be a huge opportunity in this area to provide consultancy on core business processes and merge this with IT specific knowledge.

Software is something that should be changeable in an easy form. Some people interpret this as "scriptable", but scripts are software as well and you wouldn't want to have production-editable fields that allow business people for example to modify those scripts at runtime. So there are only specific scenarios in which scripts actually add value, because if only your developers modify those scripts, why not write it in a strongly typed language instead?

Workflow based systems, due to their high decoupling factor and focus on process, might be slightly easier to change than J2EE, .NET, C++ or ASP systems. It matters from the perspective of flexibility and how you allow systems to grow with changing needs, because the needs *will* change.

Lastly, someone at JBoss mentioned how workflow systems are very much in their initial phase, comparing it to RDBMS systems. It's not very clear how they can be used effectively or in particular environments... what else we need for workflow systems to become very successful. The key part in improving these opportunities is to take the best of both worlds and merge this into something better. We may have to take a radical step into something else and see where it goes. I am just considering... wf based systems may be slightly slower due to use of XML and process persistence... but with a couple of machines and putting all processes on similar systems, what do we need for widespread deployment of this technology?

There must be things missing here, because not everyone is using it yet :).

2 comments:

Alan Kelon said...

Gerard, you may be interested in http://www.bpmi.org/

Gerard Toonstra said...

Hi Alan,

Maybe, but it doesn't look like they have any product lined up, only specifications.

Specifications are fine, but when there is a need for one. I always felt as if OMG (OhMyGod) has always ran off to specify/define the world how it should look like from their perspective without really asking if there was an actual need for any of these specifications :).

But who am I to judge? :)