Object Oriented Design
The Interactive Intelligent Kitchen Helper
The interactive Intelligent Kitchen Helper (IIKH) is a PC-based application that will
replace the index-card system of recipes found in the average kitchen. But more than
simply maintaining a database of recipes, the kitchen helper assists in the planning of
meals for an extended period – say, a week. The user of the IIKH can sit down at a
terminal, browse the database of recipes, and interactively create a series of menus. The
IIKH will automatically scale the recipes to any number of servings and will print out
menus for the entire week, for a particular day, or for a particular meal. It will also print
an integrated grocery list of all the items needed for the recipes for the entire period.
The fundamental cornerstone of object-oriented programming is to characterize software
in terms of behavior-that is, actions to be performed. Initially, the team will try to
characterize, at a very high level of abstraction, the behavior of the entire application.
This then leads to a description of the behavior of various software subsystems.
Working through scenarios
The design team first creates a number of scenarios. That is, the team acts out the running
of the application just as if it already possessed a working system. An example scenario is
shown below.
Alice Smith sits down at her computer and starts the IIKH. When the program begins, it
displays a graphical image of a recipe box and identifies itself as the IIKH, product of
IIKH incorporated. Alice presses the return button to begin.
In response to the key press, Alice is given a choice of a number of options. She elects to
browse the recipe index, looking for a recipe for salmon that she wishes to prepare for
dinner the next day. This brings up a new window in which an attractive picture of the
finished dish is displayed, along with the list of ingredients, preparation steps, and
expected preparation time.
She requests a printout of the recipe, and the output is spooled to her printer. Alice selects
“quit” from a program menu, and the application quits.
Identification of components
The engineering of a complex physical system, such as a building or an automobile
engine, is simplified by dividing the design into smaller units. So, too, the engineering of
software is simplified by the identification and development of software components. A
component is simply an abstract entity that can perform tasks that is, fulfill some
responsibilities. A component may ultimately be turned into a function, a structure or
class, or a collection of other components.
•A component must have a small, well-defined set of responsibilities.
• A component should interact with other components to the minimal extent
possible.
