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Examples and Objects

The most successful and fun project I have been part of developed a network simulator for operator training. We had a great team and freedom to work how we wanted, but another key to success was the domain model. The analyst drew object diagrams to explain to the programmers and testers how a network topology could be, for instance like this:






This may look simple, but these diagrams explained a lot to us. We used them to discuss what should happen in different scenarios, such as what should happen when a Trunk is connected to another Port. Then we implemented these scenarios as unit tests. This resulted in a robust implementation with few bugs.

But in most projects, we don't have anything like this. In one project I spent several days trying to understand how a trading system worked. I had the domain model and database schema, but it was not clear when these objects were created, updated and deleted in the database. I read thousands of lines of code and run the program in a debu…

Writing Better Requirements with Examples and Screen Sketches

We were agile, we had a Scrum master, we had standup-meetings, we had unit tests, we worked iteratively and met the product owner regularly. We did everything right, except the requirements. When we were almost ready to launch, we suddenly understood that we had missed a critical piece of functionality; namely the complex pricing model. The product owner thought we knew how this should work, but we didn't. This was not a feature that could just be patched onto the application in the end, it took several weeks of restructuring. We might blame the product owner for not communicating this clearly, but we were the software professionals. It's our responsibility to find out what our customers want.

Examples What could we have done to avoid this embarrassment? Should we have spent the first month of the project writing requirements? No, I don't think that's the solution. That might have helped, but it would have cost too much.

There is a much simpler thing we could have do…

The Future of Programming

The problem with abstractions Programmers are experts in abstract thinking. To program is to generalize: A method is a general specification of different execution paths. A class is a general specification of objects. A superclass is a generalization of several classes.

Although our minds are capable of abstract thinking, concrete thinking is more natural, and concrete examples are the foundation for abstractions. For instance, how do you teach children what a car is? You don't give a definition like: 'A car is a wheeled motor vehicle used for transporting passengers.' Instead, you point at a car and say: 'Look, a car!' After seeing a few cars, the child understands what a car is.


Notice what I just did! I started with a general principle and then gave an example. Which part of the paragraph above is easier to understand, the first sentence (general) or the rest (example)?

Einstein said that examples is not another way to teach, it is the only way to teach. It is…