Schema Translation - Information Systems Reengineering, Integration and Normalization - page 127

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Fig. 3.56 Map a foreign key into parent-child elements in XSD

into a complex element such that its component elements are mutually inclusive.
See Fig. 3.58 .

Rule 5: Mapping of Aggregation from RDB to XSD An aggregation is an
abstraction through which relationships are treated as higher-level entities. In an
XML schema, the transformation of the aggregation is to group child elements
under a parent element. In the whole-class element definition, the part-class ele-
ment is included in the attribute list of the whole-class by using the “ref” keyword
for the type parameter. See Fig. 3.59 .

Rule 6: Mapping of Categorization from RDB to XSD A categorization is a
relationship in connection with multiple superclass elements and one subclass ele-
ment. The key in the subclass element instance must refer to one of the superclass
elements. By using the “choice” keyword for making a constraint, this primitive can
be functioned in an XSD. Either element B or element C must appear as a superclass
in the subclass element A. We use the “group” feature for defining the properties on
the element side. See Fig. 3.60 .

Rule 7: Mapping of Participation from RDB to XSD The partial and total par-
ticipations can be used for distinguishing two types of relationships between parent