Schemas Integration - Information Systems Reengineering, Integration and Normalization - page 293

Case 2. One Matching Element Between Schemas A and B
Step 1. One matching element integration
In this step, it shows one matching element in schemas A and B. The solution is
to merge the matching element in schemas A and B which become an element E A1B3 .
Schema A will be base. After that, the remaining child elements in schemas A and B
will be under the element E A1B3 . And, the sibling element of E B3 in schema B will be
child elements under the parent element of E B3 in schema B in 1: n data occurrences.
Also, the parent element of element E B3 will be under element E A1B3 and become its
child element in 1:1 data occurrence (Fig. 7.26 ).
Step 2. Path Expression to Access Two XML Documents
In this case, the query statement is analyzed as a path expression without predicates.
The last element E A1B3 in the path expression will be set as a root of integrated
XML document. As the last element E A1B3 is a matching element which belongs
to documents A and B. The global query will be decomposed into two sub queries.
Two subqueries will be executed to two different XML documents. In addition, the
elements E B1 , E B4 , R B, and E B2 are reversed. Therefore, the third query is required
for generating reversed tree (Fig. 7.27 ).
Step 3. Integration for Matching Element
In this case, the integrated document contains one matching element between docu-
ments A and B. The action of data integration will handle the combination of match-