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Three Phases

The sample approach to application design methodology that is presented throughout this manual comprises the following three phases:

1. Data definition — The DBA and the systems analyst determine what element types the application needs. After defining the elements in the dictionary, the DBA then determines how the elements should be grouped into records and defines the records in the dictionary. As a result of this phase, the dictionary is populated with the element and record definitions required by the schema and subschema definitions, and with the application dialogs.
2. Database design and definition — The project leader, with the help of the DBA, designs and defines the application database, creating a schema that reflects the data access needs of the application system as a whole (that is, all the programs in the application system); subschemas are then developed that reflect the data access needs of a specific application. The database design and definition phase also deals with the physical structure of the database (that is, how the database exists on disk storage). As a result of this phase, the schema, DMCL, and subschema are defined in the dictionary.
3. Application design and development — The application development group designs and develops the applications. Dialogs are written using CA ADS process code, and dialog maps are created with the DC/UCF mapping facility. The CA ADS process code can link to routines written in source languages such as COBOL, PL/I, or Assembler. As a result of this third phase, applications exist in a form that end users can execute.