Wednesday, August 21, 2013

INFORMATION PACKAGES - A NEW CONCEPT

INFORMATION PACKAGES—A NEW CONCEPT
We will now introduce a novel idea for determining and recording information requirements for a data warehouse. This concept helps us to give a concrete form to the various insights, nebulous thoughts, and opinions expressed during the process of collecting requirements. The information packages, put together while collecting requirements are very useful or taking the development of the data 'warehouse to the next phases.

Requirements Not Fully Determinate. As we have discussed, the users arc unable to describe fully what they expect to see in the data warehouse. 'You are unable to get TA handle cm what pieces or in you want to keep in the data warehouse. You are unsure of the usage patterns. You cannot determine how each class of users will use the new system. So, when requirements cannot be fully determined. we need a new and innovative concept to gather and record the requirements. The traditional methods applicable to operational systems are not adequate in this contest we cannot start with the functions, screens and reports. We cannot begin with the data structures. We have noted that the users tend to think in terms of business dimensions and analyze measurements along such business dimensions. This is a significant observation and can form the very basis for gathering information.

The new methodology for determining requirements for a data warehouse system is based on business dimensions. It flows out of the need of the users to base their analysis on business dimensions. The new concept incorporates the basic measurements and the business dimensions along which the users analyze these basic measurements. Using the new methodology, you come up with the measurements and the relevant dimensions that must be captured and kept in the data warehouse. You come up with what is known as an information package for the specific subject.

Let us look at information package flu sales for a certain business. Figure 5-4 contains such an information package. The subject here is sales, the measured facts or the measurements that are of interest for analysis are shown in the bottom section of the package diagram. In this ease, the measurements are actual sales, forecast sales, and bud-get sales. The business dimensions along which these measurements arc to be analyzed are shown at the top of diagram as column headings. In our example, these dimensions arc lime, location, product, and demographic age group. Each of these business dimensions contains a hierarchy or levels. For example, the time dimension has the hierarchy going from year down to the level of individual day. The other intermediary levels in the time dimension could be quarter, month, and week. These levels or hierarchical components are shown in the information package diagram.

Your primary goal in the requirements definition phase is to compile information pack-ages for all the subjects for the data warehouse. Once you have firmed up the information packages. You'll be able to proceed to the other phases.

Essentitilly information packages enable you to:
  • Define the common subject areas
  • Design key business metrics
  • Decide how data must be presented
  • Determine how users will aggregate or roll up
  • Decide the data quantity for user analysis or query
  • Decide how data will be accessed 

Figure 5-4 An Information Package

  • Establish data granularity
     
  • Estimate data warehouse size
     
  • Determine the frequency for data refreshing
     
  • Ascertain how information must be packaged

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