The problem with abstractionsProgrammers 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 easier to start with a few examples and then generalize than the other way around. If you start with an abstract description, you will often try to comprehend it by visualizing an example in your head.
The problem with textAnother point is that children understand better what they see than what they hear. Or as they say, children do what you do, not what you say. This is not only true for children. We understand what we sense in fractions of a second, but words must be analyzed before they give meaning. This doesn't take long for simple sentences, but it can take hours, days or months to understand source code of any significant size. Some source code is actually incomprehensible and nobody dares to touch it.
What does this have to do with programming?As programmers, we are highly skilled in abstract thinking and textual programming languages, but when the code becomes too complex, we try to comprehend it by imagining its behavior. And when it becomes too hard to imagine the actual execution by reading the abstract code, we log what happens or run the code in a debugger. Logs and debuggers are not abstract. They give concrete descriptions of what is actually happening. They give information on method calls, object instances and variable values. This concrete information is much easier to understand than the abstract code.
We can move programming closer to how the mind works by using examples as part of the implementation. Unit testing is one way to do this, because unit tests are examples of what the code can do. There is also a growing movement for using examples as requirements. This improves the communication between users, analysts, programmers and testers. These examples can be automatically tested to connect them to the code.
Objects are examples of classesSo what is the best way to specify examples? I think that the most effective formats are user interface sketches and objects. The user interface is the best way to explain the external behavior of a program, and objects can be used to describe the internal behavior. I am not talking about technical objects that is part of the infrastructure, but domain objects that the end user understands.
Objects can be specified as text, in tables or in diagrams. Diagrams are easiest to understand, but they can be cumbersome to draw and edit.
Here is an example of an object diagram:
It is pretty obvious what this means.
If Lars sells his car to John, the objects should be changed like this:
Alternatively, the same information can be specified in tables or as text.
Modeling examples as objects is an effective way to build a domain model. This makes the examples consistent with each other and helps to reveal details and missing functionality. They are great as specification for programmers, because they are specific and contain a lot of details. And they can be automatically tested easily.
Tool SupportI believe that using examples and objects is the future of programming because it is closer to how our mind works.
I have started on a tool where you can write a specification by examples with screen sketches and objects. The application is then implemented in Groovy; a dynamic language that runs on the Java platform. The tool can test the examples to verify the program. Read more about the tool and try it out here!