Accidental Complexity

You can blame bit rot, API backwards compatibility, plain stupidity, or that we just didn't know any better at the time. Whatever the cause, we have introduced a good deal of accidental complexity over the last eight years or so, and with e4, we have a chance to reduce this or get rid of the "accidental" part altogether.

Here are some examples. If you know of other examples, please let me know!

First example: We have lots of early attempts to define API that had to be tweaked later; to see what I mean, press Ctrl+T for the Open Type dialog and enter 'I*2<' to see all the interfaces where we had to introduce a second and hopefully better version. Like IPerspectiveListener2, which was introduced in 3.0. This example is particularly embarassing, because we introduced IPerspectiveListener3 in 3.1. And, believe it or not, IPerspectiveListener4 in 3.2. Boy, am I glad that this has finally converged, or we would be looking at IPerspectiveListener7 in Eclipse 3.5.

Second example: The confusing (and untold) preferences story comes to mind, as a representative of a whole class of problems. Basically, whenever we ended up with many different ways to do the same thing, we were not able to remove old code because clients still depended on it. I am optimistic that the capabilities offered by the platform can be pared down to a manageable list. Ideally, down to something like twenty services, sometimes called "the twenty things" or the "Eclipse Application Model" in the context of e4. Like being able to persist data. Receive input. Produce selections. Schedule background work. Report progress. Provide pointers into the help system. Contribute to the menus and toolbars. And so on, but I don't have a full list at this point so I should write about it when I know more.

Third example: Like many other Java APIs, we live in a kingdom of nouns. We are sometimes joking how Eclipse, for every concept, has an adapter, a factory, and a manager. And an adapter factory, and a factory manager. Sadly, this is not a joke at all. ContextManagerFactory. ModifierHelperFactory. AbstractRefactoringDescriptorResourceMapping. I wish I could make concrete suggestions for how we can improve on this, but I am afraid we need to look at these APIs in detail. It's just a gut feeling that names with three or more three nondescript nouns are making things more complicated than necessary. By the way, my mother tongue is German, so I should be used to putting many nouns together, but I still find something like INodeAdapterFactoryManager is way over the top.

Fourth example: a good deal of complexity and bloat is caused by the proliferation of preference pages, leading to a countless number of lines of code that supports all the different combinations of all the supported preferences. Are we really helping our users by exposing and maintaining all these options?

That's it for today. I'd love to hear what you think about this, or if you have more examples of accidental complexity.

(Disclaimer: I am well aware that e4 will need to be backwards-compatible, so that 3.x plugins continue to run. When I wrote "get rid of" I meant something a little more subtle, as in "move it to compatibility plug-ins so that adopters of e4 don't have to worry about it when they develop new functionality.")

Better Than Newsgroups?

For programming-related questions and answers, check out stackoverflow.com, which launched today with a public beta. It looks very interesting - a forum, crossed with digg (user-rated), wiki capabilities (user-edited), and delicious (tags). The hope is that these three mechanisms will make the site more valuable over time, as questions are answered, rated, tagged, and edited for clarity.

Currently, the site is a bit Microsoft-heavy. For example, C# has twice as many questions as Java, and EMF refers to the vector graphics "Enhanced Metafile Format". Still, Eclipse is well represented with 58 questions compared to Netbeans with 5.

I find it amazing to watch how questions come in at a rate of roughly one per minute, and how they get answered at a similar rate. It's just like on the EMF newsgroup, but so much more Web 2.0!

Simply models

I have been working on a small demo application that (when finished) is meant to be an exemplary RCP-style desktop application based on e4. This is how it looks so far:

There is a very simple navigator on the left, a thumbnails view, and a preview area.

As I wrote the application based on Eric's and Tom's work, I started by implementing a couple of views that I contributed to the new e4 Workbench through an extension point.

Then I realized that all I need is an EMF model representing the parts that make up the UI: the views, the menu, and the toolbar. I don't actually need any extension points, because my application is not an extensible IDE - it is a rich client application for which I know how the UI should be structured. I am pretty happy about the end result - my application is fully described by one XMI file that I can edit using an editor for EMF models, and I can just go and modify that file if I want to rearrange views, add new ones, delete unnecessary ones, build my menu structure and so on.

Compare this to how it works with the current 3.x Workbench: I would have to write a perspective extension, a couple of views extensions, a command extension, a menu and a toolbar extension. Then I would have to assign unique IDs to all these pieces, and to ensure that IDs match up properly. How many hours we've wasted in the past when IDs did not match up!

Of course, this only works for closed applications, not for open and extensible ones like e.g. the Eclipse IDE. However, it is still pretty useful to be able to reason about a concrete EMF model representing the UI application structure. For example, when you have lots of little pieces contributed by many plug-ins, we can now talk about what it means to produce that concrete model from the many little pieces. One interesting question based on this is: Can we maybe generalize the many ad-hoc mechanisms we have grown over the last years (most of which involve matching up IDs) to something that is less ad-hoc and more general?

It's been fun to work on this little application so far. If you would like to participate, let us know on the e4 mailing list, and/or attend the bi-weekly e4 conference calls. You can always email me directly, of course.

P.S. The code is available in CVS - check out the ui/demos project under /cvsroot/eclipse/e4-incubator to get the launch configuration and project set file (emf-workbench.psf).