Separating business and presentation logic

In general, it is good practice to split applications into a part containing the business code that is reusable, and a part responsible for presentation to the client. This technique enables you to improve performance by optimizing the parts separately, and allows you to reuse your business logic with different forms of presentation.

When separating the business and presentation logic, you need to consider the following:

Avoid affinities between the two parts of the application.
Be aware of the DPL-restricted API; see CICS Application Programming Reference for details.
Be aware of hidden presentation dependencies, such as EIBTRMID usage.

Figure 1 illustrates a simple CICS® application that accepts data from an end user, updates a record in a file, and sends a response back to the end user. The transaction that runs this program is the second in a pseudoconversation. The first transaction has sent a BMS map to the end user's terminal, and the second transaction reads the data with the EXEC CICS RECEIVE MAP command, updates the record in the file, and sends the response with the EXEC CICS SEND MAP command.

The EXEC CICS RECEIVE and EXEC CICS SEND MAP commands are part of the transaction's presentation logic, while the EXEC CICS READ UPDATE and EXEC CICS REWRITE commands are part of the business logic.

Figure 1. CICS functions in a single application program

..
EXEC CICS RECEIVE MAP
..
EXEC CICS READ UPDATE
..
EXEC CICS REWRITE
..
EXEC CICS SEND MAP
..

A sound principle of modular programming in CICS application design is to separate the presentation logic from the business logic, and to use a communication area and the EXEC CICS LINK command to make them into a single transaction. Figure 2 and Figure 3illustrate this approach to application design.

Figure 2. Presentation logic

..
EXEC CICS RECEIVE MAP
..
EXEC CICS LINK..
..
EXEC CICS SEND MAP
..

Figure 3. Business logic

..
EXEC CICS ADDRESS COMMAREA
..
EXEC CICS READ UPDATE
..
EXEC CICS REWRITE
..
EXEC CICS RETURN..

Once the business logic of a transaction has been isolated from the presentation logic and given a communication area interface, it is available for reuse with different presentation methods. For example, you could use Distributed program link (DPL) to implement a two-tier model, or CICS Web support with the CICS business logic interface, where the presentation logic is HTTP-based.

dfhp3_concepts_buspreslogic.html | Timestamp icon

Last updated: Thursday, 27 June 2019