Extracting Domain-Based Components

Domain-Based Componentization lets you "specialize" a program based on the values of one or more variables. The specialized program is typically intended for reuse "in place," in the original application but under new external circumstances.

After a change in your business practices, for example, a program that invokes processing for a "payment type" variable could be specialized on the value PAYMENT-TYPE = "CHECK". Component Maker isolates every process dependent on the CHECK value to create a functionally complete program that processes check payments only.

Two modes of domain-based componentization are offered:

In simplified mode, you set the specialization variable to its value anywhere in the program except a data port. The value of the variable is "frozen in memory." Operations that could change the value are ignored.
In advanced mode, you set the specialization variable to its value at a data port. Subsequent operations can change the value, following the data and control flow of the program.

Use the simplified mode when you are interested only in the final value of a variable, or when a variable never receives a value from outside the program. Use the advanced mode when you need to account for data coming into a variable (when the variable's value is repeatedly reset, for example). The next two sections describe these modes in detail.

Tip: Component Maker lets you set the specialization variable to a range of values (between 1 and 10 inclusive, for example) or to multiple values (not only CHECK but CREDIT-CARD, for example). You can also set the variable to all values not in the range or set of possible values (every value but CHECK and CREDIT-CARD, for example).