Database Reference
In-Depth Information
From this narrative, an initial list of object types and associated operations can be
constructed, as shown below (Figure
A3-7
). Further refinement would be required; for
instance, additional operations may be defined for each object type (left as an exercise);
also, the data description can be further refined.
Figure A3-7.
Object Types and Operations for Purchase Order and Invoice
Receipt Subsystem
A3.8.2 The Rule-of-Thumb Approach
As an alternative to the descriptive narrative strategy, you may adopt an intuitive
approach as follows: Using principles discussed earlier, identify the main information
entities (object types) that will make up the system. Most information entities that make
up a system will be subject to some combination of the following basic operations:
•
ADD:
Addition of data items
•
MODIFY:
Update of existing data items
•
DELETE:
Deletion of existing data items
•
INQUIRE/ANALYZE:
Inquiry and/or analysis on existing
information
•
REPORT/ANALYZE:
Reporting and/or analysis of existing
information
•
RETRIEVE:
Retrieval of existing data
•
FORECAST:
Predict future data based on analysis of existing data
Obviously, not all operations will apply for all object types (data entities); also, some
object types (entities) may require additional operations. The software engineer makes
intelligent decisions about these exceptions, depending on the situation. Additionally, the
level of complexity of each operation will depend on the object type (data entity).
In a truly OO environment, the operations may be included as part of the object's
services. In a hybrid environment, the information entities may be implemented as part
of a relational database. The operations would be implemented as user interface objects
(windows, forms, etc.).
