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Chapter 8
How Many
measured end-to-end. If this happens stakeholders will instinctively tell process
stories with multiple when details, as described in Chapter 2, that represent the
milestones that must be reached to complete the process.
Retrospectively as evolving: You can remodel an evolving event from multiple
discrete events, when you discover, with the help of an event matrix, that they
represent a process sequence (as described in Chapter 4).
Adding milestone
details is straight-
forward when there
is a 1:1 relationship
between events
When an evolving
event can have
repeating
milestones, the
most recent or total
milestone details
are stored as part of
the event
Ask how many
questions to
discover repeating
milestones
Whichever route you come to it, modeling an evolving event involves adding
multiple milestone details to an event table, as in the Figure 8-4 example which
shows shipment, and delivery milestones added to CUSTOMER ORDERS. Adding
these milestone details is straightforward when there is a 1:1 relationship between
all the events, because their granularity is unchanged by merging them; for exam-
ple, if each order is associated with exactly one shipment, followed by exactly one
delivery, all the details would naturally align and no information is lost by aggre-
gating multiple events, or “made up” by allocating portions of events.
However, if an evolving event story can have repeating milestones (multiple occur-
rences of a specific milestone) there is a 1:M relationship between events, and
something has to be done to bring everything to the same granularity. For example,
if a single order line item for 100 units results in 4 staggered shipments from the
warehouse that are then batched up in 2 deliveries by the carrier, the 4 shipment
events and 2 delivery events need to be reduced to a single record to match the
order event. The simplest way to align the multiple milestones is to record the
totals for their additive quantities and the most recent values for all other details.
For example, DELIVERY DATE and CARRIER, in Figure 8-4, hold the last deliv-
ery date and the last carrier (if more than one carrier was used) and DELIVERED
QUANTITY holds the running total number of items delivered, so far, for each
order line item.
You discover the cardinality of milestones by asking how many questions about
each milestone verb—these are hidden in the prepositions for the milestone details,
particularly in the milestone when details. For the evolving CUSTOMER ORDERS
event you would ask the following questions based on SHIP DATE:
How many shipments can there be for an ordered product ?
If the stakeholders’ answer is “more than one”, you should ask:
When there is more than one ship date for an order, which
one will you use to measure the order process?
The best way to ask this type of question, about multiple milestone values, is to get
stakeholders to fill out the evolving event table with example stories.