1. EventStorming Jeppe Cramon Copyright 2015 TigerTeam ApS
Copyright Jeppe Cramon - TigerTeam ApS 2015 1 2. Why should you be
interested? Copyright Jeppe Cramon - TigerTeam ApS 2015 2 3. No
technology, framework or pattern can fix having bad or wrong
requirements Copyright Jeppe Cramon - TigerTeam ApS 2015 3 4. How
to gather requirements from many different departments/specialists?
Copyright Jeppe Cramon - TigerTeam ApS 2015 4 Department C
Department E Department A Department D Department B 5. Sequential
data gathering? Copyright Jeppe Cramon - TigerTeam ApS 2015 5 Time
6. Or design by committee? Copyright Jeppe Cramon - TigerTeam ApS
2015 6 7. Software development is journey Involving collective
learning Copyright Jeppe Cramon - TigerTeam ApS 2015 7 8. So lets
find a fun and better way to do it Copyright Jeppe Cramon -
TigerTeam ApS 2015 8 9. Event Storming Event Storming is a fun way
of bringing developers and business experts together and drive your
analysis from the outside and quickly explore complex business
domains in hours instead of days/weeks. 10. Event Storming Event
Storming (or Model storming) is a way of starting your analysis
from the outside and quickly explore complex business domains.
Invented by Alberto Brandolini See
http://ziobrando.blogspot.dk/2013/11/introducing-
event-storming.html Copyright Jeppe Cramon - TigerTeam ApS 2015 10
11. Much requirements gathering still follow in the steps of
structural or classic OO design We write use cases/stories and
afterwards look for nouns and verbs Copyright Jeppe Cramon -
TigerTeam ApS 2015 11 12. Usually we start with a simple model
Copyright Jeppe Cramon - TigerTeam ApS 2014 12 13. And as time goes
by Copyright Jeppe Cramon - TigerTeam ApS 2014 13 14. It gets more
and more complicated Copyright Jeppe Cramon - TigerTeam ApS 2014 14
15. And finally we drown Copyright Jeppe Cramon - TigerTeam ApS
2014 15 16. We end up with One Domain Model to Rule them All
Copyright Jeppe Cramon - TigerTeam ApS 2014 16 17. Cant we avoid
ceremonial modeling? Something easier, faster and better? 18. Event
Storming Invite the right people people with questions and people
with answers. They provide the perfect mix of curiosity and wisdom.
Provide unlimited modeling space Copyright Jeppe Cramon - TigerTeam
ApS 2015 18 19. Event Storming is Powerful come up with a
comprehensive model of a complete business flow in hours instead of
weeks. Engaging: bring people with the questions and people who
know the answer in the same room and to build a model together
Efficient the resulting model is perfectly aligned with Event
Sourcing and EDA, and allows for a quick determination of Bounded
Context and Aggregate boundaries and thereby also Service
boundaries Easy the notation is ultra-simple. No complex UML Fun
Eventstorming workshops and fun, people are energized and deliver
more than they expected. The right questions arise, and the
atmosphere is the right one. Copyright Jeppe Cramon - TigerTeam ApS
2015 19 20. How to run a Event Storming Workshop Explore the domain
starting from Domain/Business Events Copyright Jeppe Cramon -
TigerTeam ApS 2015 20 Event 21. Why Events Simple semantic and
notation Represent the state transitions Gives us precision Easy to
grasp by everybody in the room Place them along a timeline to
visualize the process An event might be the predecessor or the
follower of another one. Copyright Jeppe Cramon - TigerTeam ApS
2015 21 22. Events An Event message is non-prescriptive of what
should happen in other services. It leaves this open to the
recipients, so that they themselves determine what to do based on
occurrence of the event. Events always carry a name in its
past-tense form: OrderWasAccepted, OrderHasShipped,
CustomerWasReimbursed Other qualities Immutable, i.e. content
cannot be changed Always carries the ID of the Business Object it
relates to An event can and will typically will be published to
multiple consumers. The publisher of the event does not know who
the recipients are And it doesnt know what the recipients intend to
do with the event Copyright Jeppe Cramon - TigerTeam ApS 2015 22 An
Event describes something that HAS happened 23. How to run a Event
Storming Workshop What causes Domain Events? User Action model it
as a Command External system Time Other Domain Events Documents
Copyright Jeppe Cramon - TigerTeam ApS 2015 23 External Time
Command Role Event Event Document 24. Events are often the side
effect of Commands A Command message is prescriptive of what should
happen. This is a stronger form of coupling than Event and Document
messages. A Commands primary goal is to capture USER INTENT A
Command supports a single usecase and targets a single Business
Object Commands always carry a name in its imperative form:
CreateOrder, ShipOrder, CancelOrder, ReimburseCustomer, etc. Other
qualities Immutable, i.e. content cannot be changed Always carries
the ID of the Business Object that it relates to A command can only
be handled by ONE service The Operations that consume Commands dont
return values but can throw exceptions Copyright Jeppe Cramon -
TigerTeam ApS 2015 24 A command describes a Task that you want
someone else to carry out for you and the recipient can reject the
Command 25. Commands & Events Commands mutate Business Object
state which results in one or more Events being published Copyright
Jeppe Cramon - TigerTeam ApS 2015 25 Command Event(s) AcceptOrder
OrderAccepted ShipOrder OrderShipped AddComment CommentAdded
QuarantineReview ReviewQuarantined UnquarantineReview
ReviewUnquarantined 26. Commands & Events Copyright Jeppe
Cramon - TigerTeam ApS 2015 26 Receives a Command Asynchronously
Publishes multiple Events asynchronously 27. Using Business Events
to drive Business Processes Copyright Jeppe Cramon - TigerTeam ApS
2015 27 Sales Service Shipping Billing Sales Customers
MessageChannel Online Ordering System Web Shop (Composite UI)
Billing Service Shipping Service Order Accepted Event AcceptOrde r
Command The sales fulfillment processing can now begin 28. Have you
heard of flash mobs? Copyright Jeppe Cramon - TigerTeam ApS 2015 28
29. Choreographed Processes Copyright Jeppe Cramon - TigerTeam ApS
2015 29 Sales Service Order Accepted Billing Service
Orderfulfilment Service Process Manager (Saga) Shipping Service
Online Ordering System Message Channel Order Accepted Order
Accepted Customer Billed Customer Billed Order Authorized Order
Authorized 30. Documents can also drive processes Copyright Jeppe
Cramon - TigerTeam ApS 2015 30 31. Before computers Copyright Jeppe
Cramon - TigerTeam ApS 2015 31 Sales department Shipping department
Billing Department 32. Document? Copyright Jeppe Cramon - TigerTeam
ApS 2015 32 33. Example of a document driven business process
Copyright Jeppe Cramon - TigerTeam ApS 2015 33 iueiuei iueiuei
1271871 iueiuei 1271871 Customer Department Account Department
Payments Department 34. Most developers and business people are
already familiar with this way of thinking Copyright Jeppe Cramon -
TigerTeam ApS 2015 34 Todo In progress Done Work Board 35. How to
run a Event Storming Workshop Explore Aggregates Outside In An
Aggregate receives Commands and decides to execute them or reject
them If the Aggregate executes a Command it will produce one or
more Domain Events as a result Copyright Jeppe Cramon - TigerTeam
ApS 2015 35 36. Aggregates Invoice InvoiceLine * Account * What:
Cluster coherent Entities and Value Objects, with complex
associations into Aggregates with well defined boundaries. Choose
one entity to be root and control access to objects inside the
boundary through the root. External objects hold references to the
root Aggregates only refer to other aggregates by identity (their
id) Motivation: Control invariants and consistency through the
aggregate root. Enables: Loading schemes, coarse grained locking
and Ensuring consistency & transactional boundaries for
Distributed scenarios Root 37. How to run a Event Storming Workshop
Explore Sub domains Different areas of responsibility map pretty
well to different subdomains or portions of the pork Copyright
Jeppe Cramon - TigerTeam ApS 2015 37 38. How to run a Event
Storming Workshop Explore Bounded Contexts During the discussion,
some conflict areas with regards to different interpretations of
terms might emerge Draw boundaries between the multiple consistent
models that will coexist in your domain. Copyright Jeppe Cramon -
TigerTeam ApS 2015 38 Accep t Order Order Order Accepted Order
Order Delivered Sales Delivery 39. Bounded Context Domain Driven
Design (DDD) The setting in which a word or a statement appears
that determines its meaning Ensures that our is clear and precise
Copyright Jeppe Cramon - TigerTeam ApS 2014 39 40. How to run a
Event Storming Workshop Other Targets: Sketching User Personas
Sometimes the person issuing the command is important to capture
Sketching Key Acceptance Tests If the discussion revolves around
corner cases or ambiguous scenarios, remove ambiguity by defining a
clear acceptance test Sketching Key Read Models For some scenarios
what the users see is far more important than what the system does
Copyright Jeppe Cramon - TigerTeam ApS 2015 40 41. Event Storming
Legend: User Action modeled as a Command External system Time
Domain Events Documents IT Operations (Gateway) Aggregate Read
Model External Time Command Role Event Event Document IT Ops Read
Model Aggregate 42. Thank you Jeppe Cramon [email protected]
www.tigerteam.dk Twitter: @tigerteamdk and @jeppec Want to learn
more? Contact me for training and mentoring
