My first Publication Agile-Data-Warehouse-Design-eBook | Page 57

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Chapter 2
Figure 2-3
Initial event table
Several important BEAM ✲ notation conventions are indicated in Figure 2-3. The
subject (CUSTOMER) and object (PRODUCT) are capitalized, and have become
column headers. The verb (orders) is in lowercase, and is placed in its own row
above the object. This row will be used to hold other lowercase words shortly. The
capitalized column headers are the event details that will eventually become facts
or dimensions. The lowercase words will connect subsequent details to the event
and clarify their relationships with the main clause. They make event stories
readable, but are not components of the physical database design.
Draw data tables on whiteboards without borders between or below the example
rows. Fewer lines make freehand drawing quicker and neater, while at the same
time visually suggesting that the examples are open ended: that stakeholders can
add to them at any point to illustrate ever more interesting stories that help to
clarify exceptions.
Don’t name the
event until it is
complete
Leave some
working space for
detail about detail
The rest of the table is left blank, with several empty rows for example data and
space above for an event name. Don’t attempt to name the event just yet because
this may prejudice the details that the stakeholders provide.
The table is now ready to record event details and example data (event stories) to
clarify the meaning of each detail. In Figure 2-3 there is also space reserved above
the table as a scratchpad for recording detail about detail: important details that
you may capture along the way that don’t belong directly to the event (see What?
later in this chapter) but will need to be modeled as dimensional attributes after the
event is complete.