Question

I’m thinking about general modeling (diagramming) standards and tools such as BPMN, UML, data modeling, etc.

Why do we need modeling?
Usually on what phase is modeling essential for you? communication? document and report?
How can you benefit from them in work or daily life?

Thank you!

Answer 1

You coined the most important word already: communication

Not only with others, but also with your future self. If you write an application now, and return to it after a few months pause, it will be hard to find your way around. Certainly, this depends on the size and complexity of the application in question. But having some visual representation will always be helpful.

Also, diagramming the application before actual development is a great way to wrap you head around everything. Normally, you will detect problems in you initial idea that are easy to fix at that stage. And as said, these diagrams will become helpful in the future.

Showing others how the application works internally is equally important. Everybody has a different way to approach problems. So something that is intuitive for you might seem weird in someone else’s eyes. This makes it hard to grasp the concepts of an application someone else has written.

Also remember that only few of us (is any) write perfect code, and do a perfect architecture. We are human, we make errors.

Let’s say for example that there is this nifty design pattern you heard of called “decorator”, and you want to use it. Naturally, the word “decorator” will appear in your code, and people reading it will think: “Hey, I know this pattern. No need to read the gory details. I’ll just handle it as a black-box and use it.” But what if you misinterpreted the pattern and implemented it incorrectly. Now the person using it as a black-box will run into problems. These may range from small bugs to non-compiling API-calls. If you have a diagram of the whole thing, it will be much easier to pinpoint the cause.

The biggest problem with modelling is to keep the diagrams in-sync with your code. During the project life-time you will make changes. Small ones and big ones. In a perfect world, you would update the diagrams, think about it, let it sink into your brain, and then implement it. But the world’s hardly perfect. So you may end up implementing something before diagramming it (if it’s actually diagrammed at all). This whole process is cumbersome. Be it because the diagram software you use is crap or just simply because of time constraints.

Personally, I like to create an initial diagram. And once I’m happy with it, I dive into implementation. I won’t revisit the diagram for small changes. Yes, after a while the code will deviate from the diagram, but the Big Picture is still there. If I need to make a bigger architectural change, I will revisit the diagram for sure.

What I will do however is keep the in-code documentation up-to-date. Most documentation extraction tools (like javadoc) give you the possibility to use markup which is useful to make the generated docs readable and usable. Especially when using hyperlinks.

So, coming back to one of your points, where you ask what the benefit is during the daily developer life, I think that the larger diagrams don’t make that much of a difference there. Simply because once you grasped the concepts of the project, you will not need the diagram anymore as you peruse the codebase on a daily basis. What comes in handy though are proper code docstrings. Primarily because many IDEs display them while coding, or at least make it easy to jump to them. With diagrams, that’s not so much the case.

Diagrams however are useful to get started quickly with a project.

One more thought about flow-charts/activity-diagrams: I find these mostly useless. except for complex algorithms, as it helps you visualize the cyclomatic complexity. But quite honestly, I have never needed to write a complex algorithm myself. I always found ready-to-use implementation in either the standard library or in a third-party library.

And one final note: This question should have been posted on https://softwareengineering.stackexchange.com/ 😉