This document discusses event driven architecture and event processing. It defines key terms like events, event types, event processing styles, and event flows. Events are notable things that happen and can signify problems, opportunities, or deviations. Event types include ordinary and notable events. Event processing styles range from simple to complex event processing. The document outlines the common components of an event processing system including event generators, processors, channels, and reactions. It also discusses concepts like stateless and stateful event processing, event streams, and windows.

1. EVENT DRIVEN
ARCHITECTURE
VINOD WILSON – ARCHITECT – CRESTRON ELECTRONICS

2. WHAT IS IN AN EVENT?
An event is a notable thing that happens inside or outside
your business. An event (business or system) may signify a
problem or impending problem, an opportunity, a
threshold, or a deviation.

3. SPECIFICATION AND OCCURRENCE
The term event is often used interchangeably to refer to both the specification (definition) of the event,
and each individual occurrence (instance) of the event.

4. WHAT IS IN AN EVENT?
1. Event specification ID
2. Event Type
3. Event Name
4. Event Timestamp
5. Event Occurrence Number
6. Event Creator
HeaderBody

5. EVENT TYPES
• ORDINARY EVENT
• Example: Regular Temperature information
• NOTABLE EVENT
• Example: Temperature reaching above the threshold limit of 40 degrees

6. EVENT PROCESSING STYLES
• SIMPLE EVENT PROCESSING
• In simple event processing, a notable event happens, initiating downstream action(s)
• STREAM EVENT PROCESSING
• In stream event processing, both ordinary and notable events happen
• COMPLEX EVENT PROCESSING
• Complex event processing (CEP) deals with evaluating a confluence of events and then taking action
• The events (notable or ordinary) may cross event types and occur over a long period of time.
• CEP requires the employment of sophisticated event interpreters, event pattern definition and
matching, and correlation techniques
• CEP is commonly used to detect and respond to business anomalies, threats, and opportunities.

7. EVENT GENERATORS
Every event is generated from a source
Sources
1. Application
2. Data Store
3. Service
4. Business process
5. Transmitter
6. Sensor
7. Collaboration
Tool

8. EVENT PREPROCESSOR
• The processor can act as ROUTER or FILTER
• An ordinary event may be evaluated for notability by an event preprocessor (router, filter), resulting in
the generation of a new notable event.

9. EVENT CHANNEL
• The event channel, typically a messaging backbone, transports standard formatted events between
event generators, event processing engines, and downstream subscribers.

10. EVENT PROCESSING
• In the event processing layer, upon receipt, events are
evaluated against event processing rules, and actions
are initiated
• The event processing rules and actions are defined in
accordance to the needs of the interested parties, not
of the event generators.
ACTIONS
1. PUBLISH
2. NOTIFY
3. INVOKE SERVICE
4. START BUSINESS
PROCESS
5. CAPTURE
6. GENERATE EVENT
publishing the event
out to a subscription
hub
Directly notifying
humans or systems

11. EVENT REACTIONS
• Reactions to an event
Reactions
1. Automated
application
responses
2. Automated
notifications
sent to either
applications or
people
3. Human
reactions

12. MESSAGE FLOW

13. EVENT STREAM PROCESSING
• Event stream processing involves event processors receiving a number of signals from event producers
(via the event listeners) but only reacting when certain criteria are met

14. COMPLEX EVENT PROCESSING - REVERSING
• Determine event sequence that created the desired event
• CEP == AI (Artificial Intelligence)

15. EDA
• sensitive, responsive, and teachable

16. LOOSE COUPLING
• Loose coupling is the measurement of two fundamentals
• Preconception
• The amount of knowledge, prejudice, or fixed idea that a piece of software has about another piece of software
• Maintainability (Changeability)
• The level of rework required by all participants when one integrated component changes

17. ADAPTERS

18. EVENT FLOW

19. THE AGILITY CYCLE

20. SITUATION
• A situation is an event occurrence that might require a reaction
• One of the main themes in event processing is the detection and reporting of situations so that they can
be reacted to

21. EXAMPLE OF EVENT PROCESSING
Event
Generator
Event
Generator
Event
Generator
Event
Processor
Event 1
Event 2
Event 3
If certain
combinations are
measurements
are detected,
then raise alert

22. ABSENCE PATTERN OR NON-EVENT
• The fact that an event did not occur is one of the most common event processing patterns, called the
absence pattern

23. CATEGORIES OF EVENT PROCESSING APPLICATIONS

24. EVENT PROCESSING AND ITS RELATIONSHIP TO THE
REAL WORLD
• Deterministic— There is an exact mapping between a situation in the real world and its representation
in the event processing system.
• Approximate— The event processing system provides an approximation to real world events.

25. STATELESS EVENT PROCESSING
• An event processing agent is said to be stateless if the way it processes one event does not influence
the way it processes any subsequent events
• Filtering, routing and logging are all examples of stateless event processing

26. STATEFUL EVENT PROCESSING
• An event processing agent is said to be stateful if the way it processes events is influenced by more than
one input event
• An incoming event may be split into multiple events, each containing a subset of the information from
the original event
• A stream of multiple incoming events may be aggregated to produce a stream of derived events. The
derived events are typically computed from more than one event from the input stream
• Two streams of incoming events may be composed to produce a stream of derived events

27. EVENTS AND MESSAGES
• The difference here is that the event is the entity that records information about the event occurrence,
whereas the message is the mechanism used to exchange that information

28. WHAT IS AN EVENT STREAM?
• An event stream (or stream) is a set of associated events. It is often a temporally totally ordered set
(that is to say, there is a well-defined timestamp-based order to the events in the stream)
• Homogeneous event stream
• A stream in which all the events must be of the same type
• Heterogeneous event stream
• A stream in which the events may be of different types
• The stream concept can be particularly useful in applications that involve time series events, such as the
periodic reading of a sensor or periodic quotes of a stock price

29. WINDOW
• Stateful agents can be defined so that they operate only on subsets of the input events that they
receive
• In stream processing terminology, such a subset is often referred to as a window into the stream

30. SEVEN FUNDAMENTAL BUILDING BLOCKS OF EVENT
PROCESSING

31. EVENT PROCESSING AGENTS

32. CHANNEL-BASED EVENT DISTRIBUTION
• It could be an intermediary service or other piece of software (sometimes called a broker).
• It could be implemented using a multicast protocol, such as IP Multicast.
• It could be implemented using message-oriented middleware (MOM), such as a Java Message
Service (JMS) provider.

33. AN EVENT TYPE SHOULD ANSWER
• What happened?
• When did it happen?
• What other information is associated with this happening?

34. LOGICAL STRUCTURE OF AN EVENT INSTANCE

35. HEADER ATTRIBUTES
• Attributes whose values are generally set by the application: occurrence time, event certainty, and
event annotation
• Attributes whose values can be system generated: event identity, detection time, and event source

36. Thank you