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Data Warehousing and Data Mining

notes 10.5 MoLap Model

MOLAP-based products organize, navigate and analyze data typically in an aggregated form.
They require tight coupling with the applications and they depend upon a multidimensional
database (MDDB) system. Efficient implementations store the data in a way similar to the form in
which it is utilized by using improved storage techniques so as to minimize storage. Many efficient
techniques are used as spare data storage management on disk so as to improve the response
time. Some OLAP tools, as Pilot products (Software Analysis Server) introduce ‘time’ also as
an additional dimension for analysis, thereby enabling time ‘series’ analysis. Some products as
Oracle Express Server introduce strong analytical capabilities into the database itself.
Applications requiring iterative and comprehensive time series analysis of trends are well
suited for MOLAP technology (e.g. financial analysis and budgeting). Examples include Arbor
Software’s Essbase. Oracle’s Express Server, Pilot Software’s Lightship Server, Sinper’s TM/1.
Planning Science’s Gentium and Kenan Technology’s Multiway.
Some of the problems faced by users are related to maintaining support to multiple subject areas
in an RDBMS. As shown in Figure 10.13, these problems can be solved by the some vendors by
maintaining access from MOLAP tools to detailed data in and RDBMS.
This can be very useful for organizations with performance-sensitive multidimensional analysis
requirements and that have built or are in the process of building a data warehouse architecture
that contains multiple subject areas. An example would be the creation of sales data measured
by several dimensions (e.g. product and sales region) to be stored and maintained in a persistent
structure. This structure would be provided to reduce the application overhead of performing
calculations and building aggregation during initialization. These structures can be automatically
refreshed at predetermined intervals established by an administrator.

figure 10.13: MoLap architecture

10.6 conceptual Models for Multi-dimensional information

A data model is for a database designer what a box of colors is for a painter: it provides a means
for drawing representations of reality. Indeed, it has been claimed that “data modeling is an art”,
even if the product of this activity has the prosaic name of database scheme.
When a data model allows the designer to devise schemes that are easy to understand and can
be used to build a physical database with any actual software system, it is called conceptual. This
name comes from the fact that a conceptual model tends to describe concepts of the real world,
rather than the modalities for representing them in a computer.

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