12 Mining Your Own Business in Retail Using DB2 Intelligent Miner for Data
therefore also reside in the data warehouse. In this way the consistency and
reuse of data is optimized.
򐂰 Data marts are typically constructed to fit one requirement, ideally. However,
you should be aware of the trade-off between the simplicity of design (and
performance benefits) compared to the cost of administrating and maintaining
a large number of data marts.
2.2.6 Metadata
The metadata structures the information in the data warehouse in categories,
topics, groups, hierarchies and so on. They are used to provide information about
the data within a data warehouse, as given in the following list (also see
Figure 2-2):
򐂰 Metadata are subject oriented and are based on abstractions of real-world
entities, for example, project, customer, or organization.
򐂰 Metadata define the way in which the transformed data is to be interpreted,
for example, 5/9/99 = 5th September 1999 or 9th May 1999 British or
US?
򐂰 Metadata give information about related data in the data warehouse.
򐂰 Metadata estimate response time by showing the number of records to be
processed in a query.
򐂰 Metadata hold calculated fields and pre-calculated formulas to avoid
misinterpretation, and contain historical changes of a view.
Chapter 2. Business Intelligence architecture overview 13
Figure 2-2 Metadata with a central role in BI
The data warehouse administrators perspective of metadata is a full
repository and documentation of all contents and processes within the data
warehouse; from an end user perspective, metadata is the roadmap through
the information in the data warehouse.
Technical versus business metadata
Metadata users can be broadly placed into the categories of business users and
technical users. Both of these groups contain a wide variety of users of the data
warehouse metadata. They all need metadata to identify and effectively use the
information in the data warehouse.
Therefore, we can distinguish between two types of metadata that the repository
will contain technical and business metadata:
򐂰 Technical metadata
򐂰 Business metadata
Technical metadata provides accurate data in the data warehouse. In addition,
technical metadata is absolutely critical for the ongoing maintenance and growth
of the data warehouse. Without technical metadata, the task of analyzing and
implementing changes to a decision support system is significantly more difficult
and time consuming.
14 Mining Your Own Business in Retail Using DB2 Intelligent Miner for Data
The business metadata is the link between the data warehouse and the business
users. Business metadata provides these users with a road map for access to
the data in the data warehouse and its datamarts. The business users are
primarily executives or business analysts and tend to be less technical; therefore,
they need to have the DSS system defined for them in business terms. The
business metadata presents, in business terms, what reports, queries and data
are in the data warehouse; location of the data; reliability of the data; context of
the data, what transformation rules were applied; and from which legacy systems
the data was sourced.
Types of metadata sources
There are two broad types of metadata sources formal and informal metadata.
These sources comprise the business and technical metadata for an
organization.
򐂰 Formal metadata sources are those sources of metadata that have been
discussed, documented and agreed upon by the decision-makers of the
enterprise. Formal metadata is commonly stored in tools or documents that
are maintained, distributed and recognized throughout the organization.
These formal metadata sources populate both technical and business
metadata.
򐂰 Informal metadata consist of corporate knowledge, policies and guidelines
that are not in a standard form. This is the information that people already
know. This type of information is located in the company consciousness or it
could be on a note on a key employee's desk. It is not formally documented or
agreed upon; however, this knowledge is every bit as valuable as that in the
formal metadata sources. Often, informal metadata provides some of the
most valuable information, because it tends to be business related. It is
important to note that in many cases much of the business metadata is really
informal. As a result, it is critical that this metadata is captured, documented,
formalized and reflected in the data warehouse. By doing this you are taking
an informal source of metadata and transforming it into a formal source. Since
every organization differs, it is difficult to say where your informal sources of
metadata are; however, the following is a list of the most common types of
informal metadata:
Data stewardship
Business rules
Business definitions
Competitor product lists

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