Schemas Integration - Information Systems Reengineering, Integration and Normalization - page 304

7.7 Summary

We have presented a three-step schema integration methodology with proof of its
schema integration rules in terms of information dominance and equivalence in the
transformation processes. We have justified the correctness of our proposed sche-
mas' integration rules by (1) preserving data semantics between original schema
and translated schema to ensure that there is no information loss in our transforma-
tion processes, (2) most of these steps are capable of being reversed to recover the
original schema via the translated schema, and (3) preserve the database naviga-
tional paths before and after the integration of schemas.
This chapter proposes a methodology to integrate existing ORDB schemas in
relational, OO, and XML views to facilitate different application requirements. The
main objective of this methodology is to integrate existing source schemas to ful-
fill user requirements with no loss of information. A bottom-up schema integra-
tion technique is used to integrate existing object-relational schemas. Frame model
metadata, an object-relational data model, is used to capture the semantic conflicts
and other high level abstract relationships arising from the integration process. In
XML schemas integration, we preserve the data semantics according to their data
navigation paths. For example, after schema integration, the original top down
parent-to-child elements of one-to-many structure may become bottom up child-
to-parent of one-to-one structure. Therefore, the data semantics are preserved in the
original parent and child elements association. The equivalent XML elements are
matched according to their key values, which is the same criteria of RDB for the
compatibility of their relations in is-a relationship.

Questions

Questions 7.1
Can multiple relational schemas be integrated into one relational schema? Give the
rational of your answer. How can the integration of relational schemas be compared
with the integration of EER models with respect to meeting users' requirements?

Question 7.2
Provide an integrated schema for the following two views, which are merged to cre-
ate a bibliographic database. During identification of correspondences between the
two views, the users discover the followings:

1. RESEARCHER and AUTHOR are synonyms.
2. CONTRIBUTED_BY and WRITTEN_IN are synonyms,