Databases Reference
In-Depth Information
MODELING CHECKLIST
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Business requirements document
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Data source documentation, data models and/or file layouts, and defini-
tions of the data
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Flip charts
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Markers
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Tape, magnets, or pushpins to hang up flip chart pages (you could use
self-sticking flip charts too)
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A spreadsheet with each source data element
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Electronic means for documenting the business dimensional model
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Connection to the network to look at live data content
It is helpful to have three different people working electronically: one to
document the diagrams, one to takes notes for the ETL process, and one
to look at the actual data and other source system references.
Brainstorming the Framework
Begin by simply starting a list of possible dimensions and fact groups. The
intention is to get some rough ideas. Don't spend a lot of time debating whether
or not something is a dimension or will simply be an attribute. Just capture the
ideas. For the possible fact groups, think about the kinds of business processes
you are working with. How do you measure them? What is tracked about
those business events? It is helpful to think about the business itself, not what
is tracked in the computer systems.
Drafting the Initial Dimensions
Now, each of the dimensions can be designed. It is often easiest to start with
the Date dimension, which tends to be relatively straightforward and less
controversial than other dimensions.
Once you have picked which dimension you want to work on, you can look
for this type of data in the source systems. This is when the source system
analysts are valuable. Identify the lowest level of detail that exists anywhere
for that dimension. Next, add additional attributes and hierarchies. Look at the
source system reference tables, and look at the source system transaction tables
for more labels, descriptions, and groupings to include in the dimension. When
a good first draft is done, post it on the wall in the conference room. Then,
check the list for other possible dimensions to work on next.
