Next Chapter 16 Design overview:

Design overview:

The design stage takes the final specification of the system from analysis and finds the best way of fulfilling them; give the technical environment and previous decision on required level of automation.

The system design is carried out in two phases:

§ Architectural design (high level design).

§ Detailed design (low level design).

a. High Level Design:

The high-level design maps the business system described in the program requirement specification to logical data structure. It involves:

Ø Identifying the entities:

All the entities related to the module were identified, checked and consolidated.

Ø Identifying the relationship:

The relationships between entities, within and outside the system were identified.

Ø Attribute defination:

The pertaining to the entities was identified and their field characteristics were specified.

Ø Normalization:

The entities were normalized. After first and second normalization go to Dknf was achieved for all the entities of systems.

Ø Interface:

Interfacing with other system was done and attributes related to external entities were identified. Once the entities and their attributes were defined, entity relationship diagrams.

b. Low Level Design:

The low-level design maps the logical; model; have the system to a physical database design:

Ø Default database design:

This utility create column and constraint definitions form the entity model and the table / entity mapping entered in CASE* dictionary. This database design can be refined according to your application regarding using can be refined according to your application regarding using the tables, columns sand key constraint definition screen to make amendments.

The step involved here were:

· Generation of table.

· Check constraint.

· Primary key.

· Unique key.

· Foreign key.

Ø Module design:

This screen is used to enter module information during the design stage of business system development. The application systems, function, tables and columns must already exist in CASE* dictionary before being referenced.

Ø User preferences:

Based on user preference like form name, validation of primary key, layout of forms, layout of fields. Creating title for forms, mandatory input field prompts etc. was incorporated here.

Ø Generate the program:

The program was generated based on the relationship specified and according to the user preferences.

Ø Program specification:

The program specifications were written for the master, transaction, report, and queries. The logic for each fields, from were so that anyone who does not know system will be able to code the logic. Field validations and user-friendly error message were written as a part of the program specification. Identifying common procedure is yet another activity carried out in the LLd stage. This is done mainly for two reasons:

§ Saving the development time

As the procedures will be common to many programs, keeping saves the development time substantially.

§ Testing become easier

As the procedures become an independent entity, it can be easily tested.

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