programming-for-dummies

Automating Software Engineering with CASE 117
Like flowcharts, UML provides a way to visually design a program with universally
understood symbols and diagrams. Unlike flowcharts, which model
only a program’s actions, UML offers different types of models for defining a
program:
✦ Functional models
✦ Object models
✦ Dynamic models
Book I
Chapter 5
Managing Large
Projects with
Software
Engineering
You don’t have to use every type of diagram to define your program; use as
many as you need.
Of course, UML and other modeling methods are never perfect:
✦ Just because you model a program perfectly doesn’t always mean that
design is actually feasible. Many designs may look perfect on paper but
fail dramatically when put into actual use. (Think of the watertight doors
on the Titanic.)
✦ Modeling methods, such as UML, offer so many different diagrams that
it’s possible that two diagrams of the same program can describe mutually
exclusive features. Because each type of a diagram focuses on a different
view of the program, you could create conflicting designs.
Despite these problems, design methods like UML are still an improvement
over no design plans whatsoever. Just remember that UML diagrams are
meant to offer a standard way to model programs so other people can see
and understand your design before you start writing any actual code in a
specific programming language.
Functional model
A UML functional model (or a Use Case diagram) describes how a user interacts
with the program, as shown in Figure 5-3. By displaying users as stick
figures and program functions as an oval, Use Case diagrams make it easy to
see what the program is supposed to do without confusing you with how the
program will do it.
Object model
A UML object model (or a Class diagram) defines how to divide a program
into parts or objects. Each Class diagram defines an object’s name, data
(properties), and operations (methods), as shown in Figure 5-4.