Petri nets are a mathematical model that can be nicely used to express workflows. Using the petri net model, we will find out how to control the flow of a node.js program and why this can be very handy in quite a few cases.

1. Process Orchestration.
A petri net perspective

2. Overview
• petri nets
• some control flow examples
• a bit of determinism
• fitting in your code

3. Petri nets
• mathematical description language for
distributed systems
• bipartite graph
• exact mathematical definition of execution
semantics
• nondeterministic execution (unless...)

4. Petri net elements
• Place
• Transition
• Arc

5. Execution
• Tokens and markings
• Arc weight
• Capacity

6. Petri net types
• classical petri net
• colored petri net
• timed petri net
• hierarchical petri net

7. Mathy sugar
• Reachability
• and the infinite reachability graph problem
• Liveness
• dead
• potentially fireable
• can fire arbitrarily
• can fire indefinitely
• may always fire
• Boundedness
• 1-bounded (safe)
• k-bounded

8. Patterns and constructs
Sequential
FIFO queue

9. Patterns and constructs
Parallel routing

10. Patterns and constructs
Conditional routing

11. Patterns and constructs
LIFO queue

12. Patterns and constructs
Random memory for 3 memory cells

13. Patterns and constructs
Modulo 3

14. insert node
• Orchestration through high level petri nets
• potentially complex petri nets
• lightweight control structure
• correctness validation
• no ambiguity in petri net model
• functional node

15. high level petri net
• Color
• data typing and guarding
• business rules
• Time
• execution time constraints
• timed event generation
• Hierarchy
• sub nets

16. A few leverages
• workspace generation with yeoman
• functional units
• async or sync units
• hell, promises, awaiting async,....

17. Transition executions
• pass, input, output, subnet
• Standard library
• js, .net, interpreted
• synchronous or asynchronous

18. Execution policy
• input connector
• business rules
• end markings
• exception handling
• stop
• continue
• sub net

19. An example