2.2 Modeling vs. Programming
So is EMF simply a framework for describing a model and then generating other things from it? Well, basically yes, but there's an important difference. Unlike most tools of this type, EMF is truly integrated with and tuned for efficient programming. It answers the often-asked question, "Should I model or should I program?" with a resounding, "Both."
- "To model or to program, that is not the question."
How's that for a quote? With EMF, modeling and programming can be considered the same thing. Instead of forcing a separation of the high-level engineering and modeling work from the low-level implementation programming, it brings them together as two well-integrated parts of the same job. Often, especially with large applications, this kind of separation is still desirable, but with EMF the degree to which it is done is entirely up to you.
Why is modeling interesting in the first place? Well, for starters it gives you the ability to describe what your application is supposed to do (presumably) more easily than with code. This in turn can give you a solid, high-level way both to communicate the design and to generate part, if not all, of the implementation code. If you're a hard-core programmer without a lot of faith in the idea of high-level modeling, you should think of EMF as a gentle introduction to modeling, and the benefits it implies. You don't need to step up to a whole new methodology, but you can enjoy some of the benefits of modeling. Once you see the power of EMF and its generator, who knows, we might even make a modeler out of you yet!
If, on the other hand, you have already bought into the idea of modeling, and even the Model Driven Architecture (MDA) big picture,3 you should think of EMF as a technology that is moving in that direction, but more slowly than immediate widespread adoption. You can think of EMF as MDA on training wheels. We're definitely riding the bike, but we don't want to fall down and hurt ourselves by moving too fast. The problem is that high-level modeling languages need to be learned, and because we're going to need to work with (e.g., debug) generated Java code anyway, we now need to understand the mapping between them. Except for specific applications where things like state diagrams, for example, can be the most effective way to convey the behavior, in the general case, good old-fashioned Java programming is the simplest and most direct way to do the job.
From the last two paragraphs, you've probably surmised that EMF stands in the middle between two extreme views of modeling: the "I don't need modeling" crowd, and the "Modeling rules!" crowd. You might be thinking that being in the middle implies that EMF is a compromise and is reduced to the lowest common denominator. You're right about EMF being in the middle and requiring a bit of compromise from those with extreme views. However, as the designers of EMF, we truly feel that its exact position in the middle represents the right level of modeling at this point in the evolution of software development technology. We believe that EMF mixes just the right amount of modeling with programming to maximize the effectiveness of both. We must admit, though, that standing in the middle and arguing out of both sides of our mouths can get tiring!
What is this right balance between modeling and programming? An EMF model is essentially the Class Diagram subset of UML; that is, a simple model of the classes, or data, of the application. From that, a surprisingly large portion of the benefits of modeling can be had within a standard Java development environment. With EMF, there's no need for the user, or other development tools (e.g., a debugger), to understand the mapping between a high-level modeling language and the generated Java code. The mapping between an EMF model and Java is natural and simple for Java programmers to understand. At the same time, it's enough to support fine-grained data integration between applications; next to the productivity gain resulting from code generation, this is one of the most important benefits of modeling.