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Oracle Tips
by Burleson Consulting
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The Data Warehouse Development Life Cycle
Traditional Systems Analysis
There are three commonly accepted methods for systems analysis: the
Gane & Sarson method, the Ed Yourdon method, and the Tom DeMarco
systems analysis method. Recently, we have seen a new interest in
systems analysis methodologies using object orientation, with new
methodologies being introduced by Jim Rumbaugh, Peter Coad, Grady
Booch, and Schaller & Mellor. Regardless of the individual theory,
all systems analysis models share some common goals and activities.
For example, all the theories state that before any physical
construction of a system may begin, the new system must be
completely analyzed to determine all of the process logic involved
in the system. In addition, all the methodologies require
identification of the functional primitive processes and
documentation of all data stores and data flows among the processes.
The output of a system analysis is logical because no physical
constructs are introduced into the model. Physical constructs are
added in the design phase. For example, the analysis phase may
document a customer file, but developers are concerned only with
defining the data characteristics and not at all concerned about how
this file will be represented physically. Whether the customer file
is stored on Rolodex cards, an ISAM file, a BDAM file, or an Oracle
database is irrelevant in data analysis. Remember, it is the logical
specification that is used as the input in systems design. But, how
does the systems analysis change when a data warehouse system is
being developed?
Regardless of the type of system being created, a logical analysis
must always precede the start of systems design, and the design must
be completed before programming can begin. In an effort to
consolidate the systems development methodologies, research papers
have been published about the proper way to incorporate data
warehouse development into existing analysis and design
methodologies.
Fundamentally, the purpose of any systems analysis is to logically
identify the processes and the data moving between the processes,
and to describe the processing rules and data items. Only after
these items are defined can design begin, regardless of the physical
implementation of the system. To meet these goals, a data warehouse
analysis should begin with the creation of a structured
specification. A structured specification is a document which
describes all of the data, data storage, external entities, and
processes for a system. This document is then used in the design
phase for the creation of the behaviors, entity/relation model, and
class hierarchy.
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