Slides from my presentation at the iSAQB Software Architecture Gathering on Oct. 14, 2021.

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A Visual Language for
Systems Integration
A focus on essential complexity
Matt McLarty, Global Field CTO
@mattmclartybc | matt.mclarty@mulesoft.com

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A look back at 25 years of systems integration...
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1996-2002

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A look back at 25 years of systems integration...
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2003-2010

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A look back at 25 years of systems integration...
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2006-present

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A look back at 25 years of systems integration...
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2014-present

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A look back at 25 years of systems integration...
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2017-present*
*(actually 1996-present)

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The Evolution of Application Integration
7
What has changed?
Protocols
Technology
Styles
EAI Broker ESB
API
Gateway
Service
Mesh
SOA API-led Microservices Serverless

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The Evolution of Application Integration
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What hasn’t changed?
Interaction types
Interaction patterns
Composition patterns
Queries Commands Events
Request-
Reply
One-way Multicast Batch Stream
Aggregation Orchestration Choreography

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Complexity in Software Engineering
9

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Essential vs. Accidental Complexity
10
Essential Complexity Accidental Complexity
The complexity of the software’s problem
space: its functional scope and customer
needs (e.g. correlating and analyzing
large amounts of data in real time)
The complexity of the software’s solution
space: its implementation details (e.g.
the languages, processes and messages
used to do the work)

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Complexity in Integration
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Essential Complexity Accidental Complexity
Queries
Commands
Events
Request-
Reply
One-way Multicast Batch Stream
Aggregation
Orchestration
Choreography
EAI
Broker
ESB
API
Gateway
Service
Mesh
SOA
API-led
Microservices Serverless

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Power of visualization
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From https://www.ruthmalan.com/journal/journalcurrent.htm
Ruth Malan

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Visualization in Software Architecture
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DDD
Eric Evans
C4
Simon Brown
EIP
Hohpe, Wolff
From https://www.enterpriseintegrationpatterns.com/index.html
From https://martinfowler.com/bliki/BoundedContext.html Fromhttps://leanpub.com/software-architecture-for-developers

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Visualizing Interactions
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“The greatest leverage in systems architecting
is at the interfaces...
When the components of a system are highly
independent, operationally and managerially,
the architecture of the system is the
interfaces…
The components are outside the scope and
control of an architect of the whole.”
Eberhardt Rechtin, The Art of Systems Architecting
From https://sdincose.org/wp-content/uploads/2017/10/TheArtOfSystemsEngineering_inaugural.pdf

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What’s the Problem?
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How can we visually map the
integration problem space?

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Interaction Types
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Query
Command
Event
?
!
:
Interaction where a component
asks another component to provide
specific information
Interaction where a component
communicates the result of a task
to other components
Interaction where a component
asks another component to
complete a state-changing task

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Interaction Patterns
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Request-Reply
One-way
Multicast
Batch
Stream
Component sends a message to another component and
expects immediate or delayed response message
Component sends a message to another
component without expecting a response
Component sends a single message to
multiple interested components
Component sends a bounded collection
of messages to another component
Component sends an unbounded series
of messages to another component

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An Example: FlexPay
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● Mobile is transforming the payments landscape
● Customers want to be recognized for their full portfolio of
holdings with Cumulus, not just account by account
● “FlexPay” is a customer-centric, dynamic payments initiative
that removes the “single account authorization” restriction
● Payments are authorized in real time utilizing a number of data
points and customer preferences
● Payments may be posted immediately or later based on
customer preferences and situational awareness
FlexPay

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FlexPay Landscape
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Product
Proxies
Product
Proxies
Payments API
Customer
Authentication
Payments
Authorization
Payments
Fulfillment
Customer Risk
Scoring
Product
Monitor
Mobile Web
Product
Proxies
Product Systems (Accounts, Credit Cards, PLC, etc.)

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Product Activity
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Product
Proxies
Product
Proxies
Payments API
Customer
Authentication
Payments
Authorization
Payments
Fulfillment
Customer Risk
Scoring
Product
Monitor
Mobile Web
Product
Proxies
Product Systems (Accounts, Credit Cards, PLC, etc.)
:
Product Monitor
queries product
systems to report new
account activity
Product Monitor
streams account
activity to Customer
Risk Scoring service to
update customer
authorization viability
?

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Payment Authorization
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Product
Proxies
Product
Proxies
Payments API
Customer
Authentication
Payments
Authorization
Payments
Fulfillment
Customer Risk
Scoring
Product
Monitor
Mobile Web
Product
Proxies
Product Systems (Accounts, Credit Cards, PLC, etc.)
?
!
:
!
Authentication
requested for
customer
Notification that
the customer is
now online
Payment
transaction sent
for authorization
Payments Authorization
service asks for current
customer score data

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Transaction Fulfillment
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Product
Proxies
Product
Proxies
Payments API
Customer
Authentication
Payments
Authorization
Payments
Fulfillment
Customer Risk
Scoring
Product
Monitor
Mobile Web
Product
Proxies
Product Systems (Accounts, Credit Cards, PLC, etc.)
:
!
Payments Authorization
service sends
notification of approved
transaction
Daily batch of payment
transactions sent to
product systems

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FlexPay Interactions
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Product
Proxies
Product
Proxies
Payments API
Customer
Authentication
Payments
Authorization
Payments
Fulfillment
Customer Risk
Scoring
Product
Monitor
Mobile Web
Product
Proxies
Product Systems (Accounts, Credit Cards, PLC, etc.)
?
:
?
!
:
!
:
!

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How does visual modeling help?
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Getting business and
IT on the same page
Illustrating data life
cycles
Opening up external
ecosystems
Defining and evolving
service boundaries
Resolving interaction
synchronicity

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What will be addressed next?
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Composition patterns... Binding to solutions... Service design canvas...
Aggregation
Orchestration
Choreography
Whiteboards?
Specifications?
Design Studios?
From
https://dzone.com/articles/streamli
ned-microservice-design-in-practice

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Summary
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● Integration primitives and patterns are stable
● Visualization helps to model essential complexity
● The “visual language” for integration consists of:
○ Interaction types
○ Interaction patterns
● Visualizing integration has many applications

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For more information...
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Visual Integration Blog Series
The many flavours of API coordination
API interaction types
A primitive look at digital integration
A visual language for digital integration
5 ways a visual integration approach helps
Resources on Visual Software Architecture
Ruth Malan - Design Visualization: Smoke and Mirrors
Simon Brown - The C4 Model for Software Architecture
Eric Evans - At Last! Some Boundaries (Context mapping presentation)

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Thank you!