COMPLETING THE LOGICAL DESIGN - Database Design and Development: An Essential Guide for IT Professionals - page 340

• Mapping of each individual component of the consolidated semantic data
model to one or more components of the relational data model
• Completion of the relational data model schema, expressed with standard
conventions and notations
• List of any special considerations
Usage of Outputs
The outputs from the logical design step serve both users and database developers.
This point in the database development life cycle is a good time to review the seman-
tic data model diagram with the key users and get their further confirmation. In the
requirements definition document, the users get the initial knowledge of how real-
world information requirements are reviewed and captured. But the semantic data
model crystallizes the representation of real-world information requirements in a
clearer manner. You can walk the key users through the semantic model diagram,
explain how the model is a true replica of real-world information, and relate the
components of the model to the business processes in which the users are engaged.
When the data modelers and designers review the consolidated semantic model
diagram, they can ensure that nothing is missed from the requirements definition.
The completeness of the model is the confirmation of one major step in the data-
base development life cycle.
Database administration function is more concerned with the completeness
of the relational schema. This forms the basis for the physical design. In addition,
database administrators also need information for defining the data views to the
database management system. As you recall, each data view is the portion of
the database in which a particular user group is interested. The data views form the
external schemas. All the data views combined together make up the complete
logical schema.
Use of CASE Tools
CASE (Computer-Aided Software Engineering) tools offer major benefits during
the logical design step in the database development life cycle. You can use drag-
and-drop techniques to create semantic data models. The ease of use of most of
the data modeling tools provides enormous advantages and saves considerable
time for data modelers in completing their tasks. The software tools generate the
outputs in the form of E-R diagrams, supporting the standard methods for data
modeling.
In addition to providing facilities for creating semantic data models, most of the
CASE tools contain features known as forward engineering and backward
engineering.
Forward Engineering. As soon as a generic semantic data model is created with
the CASE tool, you can use this feature to transform the logical data model into a
physical data model for the target database system. The database administrator can
use this powerful feature to take the physical schema generated by the forward engi-
neering feature and define the database in the data dictionary of the target DBMS.