I’ve been pondering what the fundamental problems are that we and others are trying to solve with DSLs, Software Factories, Model Driven Software Development, and the like. I’ve distilled it down to two key problems:
- Automating rote tasks that are tedious and time-consuming to perform, and error-prone when done manually. I.e. How can we build (and evolve) more reliable systems, faster?
- Establishing and maintaining the connection between business requirements and the systems built to help meet those requirements. I.e. How do we ensure that the right system is built (and continues to be the right one)?
DSLs help with the first of these because they let you codify information that would otherwise be scattered and repeated in many development artefacts. The idea is that to change that information you change it in a single domain specific viewpoint or model, and the changes are propagated to all the artefacts that would otherwise need to be changed by hand. Of course the interesting problem here is how the propagation is performed, and one common approach is to propagate by regenerating the development artefacts by merging the information in the domain specific model with boilerplate. This works best if you can separate out generated aspects of artefacts from hand written aspects, for example by using C# partial classes. In this way you avoid that task of copying boilerplate code and making changes in designated places, and when things change you avoid multiple manual updates.
If it is not possible to cleanly separate the generated aspects from the hand written ones then more sophisticated synchronization techniques will be required, but I’m not going to go into that now.
And once you start thinking in this way, you then discover you can have multiple domain specific viewpoints contributing different aspects to your development artefacts. And then you discover that you can relate these viewpoints, synchronizing information between them and generating one from another. You’re treading a path towards software factories.
Domain specific models created to help solve the first problem, also tend to be more abstract and provide new perspectives on the system. They hide detail and can reveal connections that it is difficult to find by looking directly at the development artefacts, especially when those models are visualized through diagrams. This contributes to the second problem: they provide viewpoints on the system which it is often easier to connect to business requirements. One can then go a step further, and build new viewpoints specifically focused on expressing and communicating the business requirements, and set up connections between those viewpoints and viewpoints of the system which can be monitored and synchronized as one or other change.
We see customers already leveraging such techniques in their development processes, codifying their DSLs using XML or UML + stereotypes & tagged values, for example. They also tell us they are having problems with these technologies, and it is those problems that we’re trying to address with DSL tools. I’ll go into more depth on this, and reveal more of what we’re planning to help solve these problems, in future posts.