Domain Driven Design and Event Sourcing with RIM

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Domain Driven Design and Event Sourcing with RIM
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Introduction
RIMResistance is Futile, you Will be Assimilated!
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DDD and Event Sourcing

• Introduction
• George de la Torre
• Developer of custom clinical apps
• For a long time
• Discovered RIM a long time ago
• Oleg Sitalo (silent partner)
• Developer of custom clinical apps
• For a long time together
• Believes in RIM, at occasions

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DDD and Event Sourcing

• Agenda
• Google will find heaps of stuff on this
• Will focus on the RIM stuff
• Great resources for DDD/ES
• http//msdn.microsoft.com/en-us/library/jj554200.a
  spx
• Implementing Doman-Driven Design
• Vaughn Vernon
• Domain Driven Design (the Blue Book)
• Eric Evans

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DDD and Event Sourcing

• Domain Driven Design
• Object Oriented Model
• Business needs language captured
• HL7 v3 RIM benefits
• Design done! the hardest part
• Standard open shared to all
• Deep insights into domain knowledge
• Integration of domains built in (No barriers!)
• Reuse logic across clinical domains

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Domain ModelBlueprint for all Aggregates
HL7 V3 RIM
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Supporting DomainsExternal Services
Vocabulary
Bounded Contexts
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Supporting DomainsExternal Services
Anti Corruption Layer
Other systems or Big Ball of Mud
Business Process and Rules Engines
Point This layer keeps RIM pure!
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DDD and Event Sourcing

• Event Sourcing
• Only the Aggregate (D-MIM) is persisted
• The command is saved (Behavior)
• Aggregates publishes the events
• Command Query Responsibility Segregation (CQRS)
• Command (Transaction) Model
• Query Model

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Patient Dashboard ExampleUse Case

• Schedule a patient visit
• Find Patient (Query Model)
• View Calendar (Query Model)
• Patient assigned time slot (Command)
• CreateAppointmentCommand(data) executes
• Scheduling aggregate is created from data
• The created aggregate is appended
• Publishes event to update Query Model

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Scheduling AggregateExample
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Scheduling AggregateCMET (PAT) is the Root
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Scheduling Aggregate

• Considerations
• Entity is usually the Root
• No cloning, only class codes
• Aggregates varies with the RIM set
• Act may be the Root (Strategy)
• Reference others Aggregates (Observations)
• Act Mood partitioning
• PHI segregation requirement (Query model too)
• Performance

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Scheduling Aggregate

• Considerations continued
• Serialized, XML, JSON, etc
• Relational Database (SQL)
• Cache based systems
• File systems
• NoSQL
• Natural for event stores
• Easier to query Aggregates if needed
• Aggregates loaded for logic on command

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Scheduling AggregateAppended
CreateAppointmentCommand(data)
Event Store
ID Name Version Data
1 Schedule 1.2
2 Schedule 1.2
3 Schedule 1.2
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Scheduling AggregatePublishes Events
AppointmentCreatedEvent(data)
UpdateDatabaseView()

Query model
MRN First Last DOB Phone Start End Note


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Scheduling AggregatePublishes Events
AppointmentCreatedEvent()
CreateAdmissionMessage()

HL7 2.x
MSH\ADT1MCMLABADTMCM198808181126SECURITY
ADTA01MSG00001-P2.3 EVNA01198808181123 PID
PATID12345M11JONESWILLIAMAIII19610615M
-C1200 N ELM STREETGREENSBORONC27401-1020G
L(91-9)379-1212(919)271- 3434SPATID12345001
2M101234567899-87654NC
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Scheduling AggregatePublishes Events
AppointmentCreatedEvent()
UpdateDataMart()

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Patient Dashboard ExampleTwo Separate Models
(CQRS)

• Domain (Transaction) Model
• Complex structure (RIM)
• Aggregates are only created from RIM
• Aggregates are appended (Write Only)
• Query Model
• Simplified model structure (SQL)
• Multiple models created as needed
• Model optimized for querying (Read Only)

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Simple Component DesignCQRS