Beginning Java Objects: Chapter 2
Abstraction and Modeling
Abstraction as the Basis for Software Development
When pinning down the requirements for an information systems development project, we typically
start by gathering details about the real world situation on which the system is to be based. These details
are usually a combination of:
- Those that are explicitly offered to us as we interview the intended users of the system.
- Those that we otherwise observe.
We must make a judgment call as to which of these details are relevant to the system's ultimate purpose.
This is essential, as we cannot automate them all! To include too much detail is to overly complicate the
resultant system, making it that much more difficult to design, program, test, debug, document,
maintain, and extend in the future.
As with all abstractions, all of our decisions of inclusion versus elimination when building a software
system must be made within the context of the overall purpose and domain, or subject matter focus, of
the future system. When representing a person in a software system, for example, is their eye color
important? How about their genetic profile? Salary? Hobbies? The answer is, any of these features of a
person may be relevant or irrelevant, depending on whether the system to be developed is a:
- Payroll system
- Marketing demographics system
- Optometrist's patient database
- FBI 'most wanted criminals' tracking system
- Public library
Once we've determined the essential aspects of a situation — something that we'll learn how to do in Part
2 of this book — we can prepare a model of that situation. Modeling is the process by which we develop
a pattern for something to be made. A blueprint for a custom home, a schematic diagram of a printed
circuit, and a cookie cutter are all examples of such patterns. As we will learn in Parts 2 and 3, an object
model of a software system is such a pattern. Modeling and abstraction go hand in hand, because a
model is essentially a physical or graphical portrayal of an abstraction; before we can model something
effectively, we must have determined the essential details of the subject to be modeled.
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