Cross-Dimension Attributes
Definition 9: A cross-dimension attribute is a (either dimension or descriptive)
attribute whose value is determined by the combination of two or
more dimension attributes, possibly belonging to different hierarchies. It
is denoted by connecting through a curve line the arcs that determine it.
For instance, if the VAT on a product depends on both the product category and the
state where the product is sold, it can be represented by a cross-dimension attribute
as shown in Figure 4.
Conceptual Modeling Solutions for the Data Warehouse
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Convergence
Consider the geographic hierarchy on dimension customer (Figure 4): customers live
in cities, which are grouped into states belonging to nations. Suppose that customers
are grouped into sales districts as well, and that no inclusion relationships exist
between districts and cities/states; on the other hand, sales districts never cross the
nation boundaries. In this case, each customer belongs to exactly one nation whichever
of the two paths is followed (customer ?†’ city ?†’ state ?†’ nation or customer ?†’
sales district ?†’ nat on).
Definition 10: A convergence takes place when two dimension attributes
within a hierarchy are connected by two or more alternative paths of
many-to-one associations.
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