Schema Translation - Information Systems Reengineering, Integration and Normalization - page 128

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Fig. 3.57 Map isa relationship into element extension in XSD

and child entities. A total participation means a mandatory relationship between
parent and child elements. In an XSD, there is a more flexible way to maintain the
referential integrity by using an attribute group, element group, or global element
with “minOccurs” and “maxOccurs.” See Fig. 3.61 .

Rule 8: Mapping of Cardinality from RDB to XSD We capture 1:1, 1:n, and m:n
cardinalities in this step. A cardinality in the XSD Graph is represented as a sub-
element or a global element. The name of the associating element is the association
name in an m:n relationship. The associating element could be treated as a pointer
referring to the associated elements and is assisted by the keyword of “minOccurs”
defined on the element declaration. If an element is referred to by two or many ele-
ments, it is treated as a global element in the 1:1 and 1:n cardinalities. See Fig. 3.62 .

Rule 9: Mapping of n-ary Relationship from RDB to XSD We apply the concept
of a ternary relationship from an EER model into an XSD Graph. The relationship
relation is placed at the centre of three related relations in an EER diagram. In the
XSD Graph, the three related relations are mapped into three associated elements.
The relationship relation is mapped into a “group element” function. The occurrences