Time for Event driven SOA
Prasad Bonthala
Senior Project Leader
ADP Private Limited

Contents
Introduction
Necessity
SOA
EDA
Event Driven SOA
Summary

Introduction
Experts agree that SOA is the best approach for new
Enterprise Architecture development
It is also possible that you have already started
working towards it
But the question is ‘Are you implementing the right
SOA’ keeping long term objectives in mind?
You may not be if you have not thought about EDA
This presentation talks about the necessity and key
benefits with the marriage of SOA and EDA

Necessity
Companies face large number of complex events
every day and responses are expected in real time
Real time trade settlement systems
Flight reservation system
Streaming stock data
Real time vehicle location for transportation
companies
SOA is good if our requirement is just to send
requests and receive responses synchronously
But not good enough to handle real time events
asynchronously

Necessity
Event-Driven SOA combines SOA’s request–response
and EDA’s event publish-subscribe paradigms
Also referred as “Business Driven Architecture”
Allows system designers to support both events and
services
It enables designers to map the application design to
the business problem which consists of both events
and services
Results in extreme agility, enabling enterprises to
conduct business at light speed

Service Oriented Architecture
(SOA)
SOA is a business-centric IT architectural approach
It is about better alignment of business and IT
through business processes and services
To create more agile and dynamic IT that can respond
quickly to new business opportunities, requirements,
and threats by quickly developing and deploying new
capabilities from putting together composite
applications from reusable business services

SOA
To get away from an isolationist practice in software
development, where each department builds its own
system without any knowledge of what has already
been done by others in the organization
This approach leads to inefficient and costly situations
where the same functionality is developed, deployed
and maintained multiple times
SOA is based on a service portfolio shared across the
organization and it provides a way to efficiently reuse
and integrate existing assets

SOA
SOA is based on a conventional request-response
mechanism

Event Driven Architecture (EDA)
What is an event?
Notable thing that happens inside or outside of your
business
An event may signify a problem, an opportunity, a
deviation, or a threshold
Each event occurrence has an event header and an
event body
Event header contains elements describing the event
occurrence
details like specification ID, event type, name, creator,
time stamp etc
Event body describes what happened

EDA
Ex: Integrated Flight Booking System
‘Flight Delayed’ event
Event body would contain the information to
communicate which flight is delayed and by how many
hours etc
Event body should be fully described so that interested
parties can use that information to take necessary
actions like re booking the transit passengers who are
on the delayed flight to another available flight
automatically
If the event is not fully described subscribers might
have to communicate with the source system to get
required information

EDA
In an event driven architecture, an event happens
inside or outside of your business, which disseminates
immediately to all event subscribers
The event subscribers evaluate the event and takes
appropriate action
An event driven architecture is extremely loosely
coupled and highly distributed
Creator has no knowledge about events subsequent
processing
Event driven architectures are best used for
asynchronous communication

EDA

Event-Driven SOA
The occurrence of an event can trigger the invocation of one
or many services
Upon generation, the event is notified to all interested
parties
The interested parties evaluate the event and optionally
take an action
The action may include invocation of service(s)
Those services may perform a simple action or an entire
business process
This interaction between events and services is commonly
referred to as Event-Driven SOA

ESB
ESB is today’s most effective way to address complex
integration challenges
It provides efficient connectivity between dissimilar
applications
It combines event-driven and service oriented
approaches to simplify integration of business units,
bridging heterogeneous platforms and environments
Acts as an intermediary layer to enable communication
between different application processes
It supports synchronous and asynchronous
communication

ESB

Summary
EDA does not replace SOA, but rather, complements it
In the service oriented architecture you have a
request that you send and you control what happens
But in the case of even driven architecture, you react
to things as and when they happen
Both have similar underlying infrastructure to talk to
various systems, to carry information from one place
to another, to transform messages that are flowing
through and to process business rules

Summary
An optimized business needs to handle both services
and events to enable extreme transaction processing
Event Driven SOA (also referred as Business
Driven Architecture) combines the power of both
SOA and EDA to address all the capabilities needed to
respond to the real-time business dynamics