The document outlines a presentation on actor models and finite state machines (FSM) in software design, emphasizing that all computations occur within actors and communication is message-based. It details FSMs as a modeling technique which allows actors to change states and behaviors based on events, illustrated with an inventory system case study. Additionally, it mentions topics not covered in depth, including shared state, persistence, and best practices for using Akka.

1. By:
Harmeet Singh (Taara)
Software Consultant

2. Agenda
1. Actor Model/Akka (Brief)
.
2. Finite State Machine (FSM)
3. Demo.
4. Leftover: The things we didn’t cover

5. ActorModel:Fundamentals
➔ All Computations is performed within Actor.
➔ Actors can communicate only through messages.
NOTE: Modeling a software this allows you to deal
with state in an atomic way, isolated way which is
core principal of actor model.

6. ActorModel:Fundamentals
➔ In response to a message, an actors can:
– Change its State or Behavior
– Send message to other actors.
– Create a finite number of child's

7. ActorModel:Fundamentals
-Actors can change their State or Behavior
➔ Each behavior in the system can represent a state,
and the actor can move from one state to the next
when its receives a message. There are few
mechanism we can use to change behavior in the face
of different states:
– Conditional Based on an Actor State.
– Hotswat: become() and unbecome().
– Finite State Machine (FSM).

8. FiniteStateMachine(FSM):
-Actors can change their State or Behavior
If we are in state S and the event E occurs, we
should perform the actions A and make a
transition to the state S'.
State(S) x Event(E) -> Actions (A), State(S')

9. Finite State Machine (FSM)
➔ Common language independent modeling technique.
➔ FSM is defined by a number of states and the
different triggers for all possible transitions.
➔ Transitions are only happen when the machine is
trigger by an event.
➔ Event in an Akka FSM are the messages that actor
received.

10. FiniteStateMachine(FSM):
-Visualize FSM

11. FiniteStateMachine(FSM)
–Case Study: Inventory System

12. FiniteStateMachine(FSM)
Case Study: Inventory System
Akka-FSM

13. FiniteStateMachine(FSM)
-User Cases
➔ Change actors behaviors according to state.
➔ Perform transitions during actor state change.
➔ Finite number of states.
➔ Model pure actor model using DDD.

14. Leftover:Thethingswedidn’tcover
➔ Shared state with Agents.
➔ Akka persistence.
➔ Actor Model with DDD (Domain Driven Design).
➔ Akka best Practices.

15. References:
➔ Applied Akka Patterns By
Michael Nash and Wade Waldron.
➔ Learning Akka By Jason Goodwin.
➔ Akka in Action By
Raymond Roestenburg (Author) , Rob Bakker (Author) and Rob W