Improving Expressive Power in Modeling Data Warehouse and OLAP Applications - Evolving Application Domains of Data Warehousing and Mining - page 21

Figure 2. An extract of the AdventureWorksDW schema

by the DimSalesTerritory table, which allows
decision-making users to analyze measures con-
sidering the geographical distribution of a sales
organization. The DimReseller table in Figure 2
includes stores that resell products and has attached
the table DimGeography , which indicates geo-
graphical distribution of these stores. In addition,
this schema contains an employee dimension (the
DimEmployee table in the figure) with an organi-
zational hierarchy of supervisors and subordinates.
We slightly modified the DimEmployee table and
deleted the attribute DepartmentName . Instead,
we created a new table that represents different
departments. Since we assigned some employees
to two different departments, we had to create
an additional table (the EmplDepBridge table in
Figure 2). This table represents all assignments
of employees to their corresponding departments
and, in addition, includes an attribute called Dis-
tributingFactor that indicates how to distribute
measures between different departments for em-
ployees that work in more than one department,

e.g., assign 70% of sales to the department 10 and
30% of sales to the department 14.
As can be seen in Figure 2, even though there
are several hierarchies that users are interested
in exploring, only the hierarchy represented as
snowflake schema (e.g., Product - Subcategory -
Category ) can be distinguished. We will see in
the next section how this situation can be changed
using a conceptual model.

conceptual representation

The MultiDim model (Malinowski & Zimányi,
2008) is a multidimensional model that allows
designers to represent at the conceptual level all
elements required in DW and OLAP applica-
tions, i.e., dimensions, hierarchies, and facts with
associated measures. In order to present a brief
overview of the model 2 , we use the example in
Figure 3. The schema in this figure corresponds
to the logical schema in Figure 2. We include in
the schema only those hierarchies that are relevant