Databases Reference
In-Depth Information
Natural
language
interface
Formal and
semiformal
interface
Graphical
interface
User/designer
Knowledge
Acquisition
Paraphrasing/
validation
Domain and
application
knowledge
Data abstraction and structuring
VIEW3
VIEW1
VIEW2
Linguistic
knowledge
View integration
Conceptual
schema
Verification
Reverse
engineering
Rules, dependencies
Transformation and normalization
Logical
schema
Technical
knowledge
Reverse
engineering
Optimization
Access frequency, workload
Physical
schema
Figure 13.3
A framework for DB design environment.
the target information system, the conceptual schema may either be obtained
in one shot or after the integration of several separate schemas that corre-
spond to different user views. Reverse engineering is another way to abstract
conceptual entities and relationships from existing files or DBs.
Verification checks the formal verification of the conceptual model,
and validation checks its relevance to user requirements. Formal verification
guarantees consistency, irredundancy, and completeness. Formal verification
techniques depend on the conceptual model used. Conformance with user
requirements is much harder. It is usually based on heuristics, expert rules,
and prototyping. Validation is the most powerful aid that CASE tools can
provide. Indeed, the minimum requirement expected from a CASE tool is at
least to check that the design is correct.
