Database Reference
In-Depth Information
Example 14:
Replace the calculus specification in example 12 with an algebra
specification.
The two solutions are illustrated in Figure
8-4
. Note that existential quantifiers are
ignored in the translation process as long as the quantified variables are not implicated
as part of retrieved attribute-list (hence the rule towards the beginning of the previous
section). Also recall that existential qualifiers can effectively replace universal quantifiers.
Figure 8-4a.
Graphical Representation of Non-optimized Solution to Example 12
