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It is sometimes necessary to provide either a copy or a sample of the data as part of the metadata. For example, one may want
to specify during the design phase what will be the content of a Gender table. This is similar to the use of Collaboration
diagrams in UML.
Figure 6-13
shows how a Rowset inherits from Extent, from the Foundation package. It represents all the data comprised in a ColumnSet.
A RowSet can only be owned by a ColumnSet or any derived class. A RowSet contains Rows. Row inherits from Object. Its structure
is defined by the corresponding ColumnSet and its Columns. Each Row is divided into ColumnValues, which match the value of
a relational table, at the intersection of a row and a column. ColumnValue inherits from DataValue from ObjectModel.
Package (from Core)
/feature Attribute (from Core)
Figure 6-13 Relational Instance classes
Figure 6-14
shows a collaboration diagram, we show how the instances for the two column, two row Gender table are represented, and how
they are associated with the Gender table definition. Two kinds of Instances are instantiated: Row and ColumnValue. The Row
is associated with the AttributeLink through the instance/slot association. The ColumnValue is associated with the AttributeLink
through the value association. While not shown on the diagram to keep it readable, each Instance is associated with a Class:
the Row would be associated with the ColumnSet, and the ColumnValue with the SQLType of the corresponding Column.
Gender : Table : RowSet
: Slot
M : ColumnValue
: Slot
Male : ColumnValue
: Slot
F : ColumnValue
Female : ColumnValue : Row
Code : Column
Name : Column
Figure 6-14 Collaboration diagram showing use of instance classes