My first Publication Agile-Data-Warehouse-Design-eBook | Page 143

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Chapter 4
Adding New Examples to Conformed Dimensions
Ask for any new
examples needed to
cover the five event
story themes and
describe new
dimensional roles
Test conformed
dimensions by
adding new
examples
You not only want stories to relate new events to existing events, you also want
them to tell you as much as possible about each new event detail. You make sure
that they do by asking for typical, different, repeat, missing, and group themed
stories, as described in Chapter 2. To cover all these themes and illustrate new roles
for role-playing dimensions you will need examples that are not present in any
BEAM ✲ tables modeled so far.
When stakeholders give you new examples try adding them to the appropriate
dimension before using them in event stories. Apart from allowing you to use the
examples by abbreviation, filling out their dimensional attributes is also a great test
of conformance that helps you to spot missing or non-conformed attributes. For
role-playing dimensions, you may have to adjust some existing attributes to match
new roles; e.g., COMMISSION is a mandatory (MD) attribute of SALESPERSON,
but would be a non-mandatory exclusive (X) attribute of a conformed EMPLOYEE
[RP] dimension that must play the role of warehouse worker as well as salesperson.
Asking for examples encourages everyone to define and use conformed dimen-
sions. Why make up new example values when you can copy them from a con-
formed BEAM✲ dimension table?
Modeling New Details and Dimensions
Ask for additional
when details before
copying more
dimensions from
the matrix
Don’t forget to
check for additional
who, what, where,
why and how details
too and add them to
the matrix
Mark new details
with a [?] type as a
reminder to model
their dimensional
attributes
After you have filled in the themed examples for who (WAREHOUSE WORKER),
what (PRODUCT), and when (SHIP DATE), proceed through the 7Ws in BEAM ✲
order (see Figure 2-2) by asking for any other when details before moving on to
who, and what, and where. For each of these W-types copy the relevant dimensions,
one at a time from the matrix, and ask for examples.
Before you move on to the next W-type always check for additional details of the
current type. Seeing the event stories build up will often prompt stakeholders to
suggest additional details they couldn’t think of when modeling at the matrix
summary level. As soon as stakeholders confirm any additional who, what, where,
why or how detail with relevant examples, add them to the matrix where they too
might become conformed dimensions.
Figure 4-20 shows four who, and where details added to the shipping event.
CUSTOMER and DELIVERY ADDRESS, with their highly abbreviated examples,
are conformed dimensions, while CARRIER and WAREHOUSE are new and have
not been modeled as dimension tables yet. Any new details/dimensions, like these,
can be marked as type [?] as a reminder that, while they maybe on the matrix, they
still need to be modeled at the attribute level, with examples, when the event is
completed.