Page 194 - DCAP603_DATAWARE_HOUSING_AND_DATAMINING

Data Warehousing and Data Mining

notes 10.1 Multi-dimensional view of information

The multi-dimensional data model and view of information depend upon various types of
multidimensional data models information and how it is implemented in relational tables and
standard form analytic workspaces. It consists of the following topics:

1. The Logical Multi-dimensional Data Model
2. The Relational Implementation of the Model
3. Conceptual Model for Multi-dimensional Information

10.2 the Logical Model for Multi-dimensional information

Data warehouses and OLAP tools are based on a multi-dimensional data model. It is designed to
solve complex queries in real time. The central attraction of the dimensional model of a business
is its simplicity which is the fundamental key that allows users to understand databases, and
allows software to navigate databases efficiently.
The multi-dimensional data model is composed of logical cubes, measures, dimensions,
hierarchies, levels, and attributes. Figure 10.1 shows the relationships among the logical objects.

figure 10.1: Logical Multi-dimensional Model

Logical Cubes: Logical cubes provide a means of organising measures that have the same
shape, that is, they have the exact same dimensions. Measures in the same cube have the same
relationships to other logical objects and can easily be analysed and displayed together.
Logical Measures: Measures populate the cells of a logical cube with the facts collected about
business operations. Measures are organised by dimensions, which typically include a Time
dimension.
Measures are static and consistent while analysts are using them to inform their decisions. They
are updated in a batch window at regular intervals: weekly, daily, or periodically throughout the
day. Many applications refresh their data by adding periods to the time dimension of a measure,
and may also roll off an equal number of the oldest time periods. Each update provides a fixed
historical record of a particular business activity for that interval. Other applications do a full
rebuild of their data rather than performing incremental updates.

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