Source Code is the Design
Following a DesignFest @ Directi, there has been a lot of discussion on “what is Design?”, “should one design before they code?” and so on.
In this blog I’ll be mostly focusing on object design. There are other designs related to Usability which is not the focus. However I believe it is very important to incorporate various other design elements into your object design to achieve Conceptual Integrity.
I strongly recommend you read the following before you continue reading this blog:
So where does this whole notion of design followed by coding come from?
On the C2 Wiki there is a really nice response to this question:
I propose that the real issue is that design is not really a beneficial activity in software development, and to say “The Source Code Is The Design” is trying to use semantics to gloss over the issue.
I feel this is an important distinction if the goal is to remove the “design” stage from the software development process. Rather than being afraid of being accused of “not doing design”, we need to turn the debate around to be “Why should we do design?”
For some tasks (in other industries like Manufacturing), it may be much more cost effective to create a design and evaluate the design before building the actual product. For software, this is not the case. For years, software has struggled to come up with something to use for “design.” We had flow charts, PDL, Data Flow Diagrams, prose descriptions, and now UML. With software, however, it takes as much time to create the design as the actual software; the design is more difficult to validate than the actual software; and the simplifying assumptions made in the design are often the critical issues to evaluate in the software. For these reasons, it simply is not cost effective to design, iteratively correct the design, then write the software (and then iteratively correct the software). It is better to start with the software and iteratively correct it.
I believe it is time to explicitly state the long held secret of software, we do not need to do design; design is ineffective and costly.
I would saying mandating that you need to design first does not seem right. It’s also important to understand that:
UML diagrams and other associated paperwork (if any) are documentation about the design. A documentation can have different views as appropriate to shed some light (if any) on various aspects of the object described. However, the source code has a privileged status: it is not just “documentation about”, it is the object itself.
If documentation is important why not use source code as that document? Of course this means programmers will now have to write self-documenting code which embraces Simple Design.
