Quadratic equation as example in bpmn and camunda

1. BPMN processes
Example for students. Quadratic equation

2. D=b*b — 4ac
a b,c
End
D > 0?
start
No solutions
Roots х1,х2
x1=(-b + sqrt(D))/ 2a
x1=(-b - sqrt(D))/ 2a
We going to make process, that
will calculate roots for quadratic
equation

3. Preparations:
1. We need database with all data for camunda
2. We need docker with camunda runned on http://localhost:8651/camunda
3. We need camunda modeler - https://camunda.com/download/modeler/
4. Maybe someone need explanation for quadratic equation
- https://en.wikipedia.org/wiki/Quadratic_equation

4. Start Camunda modeler and create
bpmn process

5. Process decomposition

6. Add data flow

7. Add user variables —
a, b, c

9. Make this flow by default, if
discriminant less or equal zero

10. This flow is marked with line

11. This flow will have condition

12. Add Х1 calculation

13. Add Х2 calculation

14. To get result, just set X1 and X2
variables in form

15. Restart containers with database and camunda

16. tail -n 5 camunda/logs/catalina [TAB]
Looks like everything OK

17. Upload our process to Camunda

18. Should not be “Failed” message

21. Our user, that was registered in
Camunda

22. Go to configuration cockpit

23. Uploaded processes

24. We will clean any other deployments except quadratic_equation

26. Should be only one deployment left

27. Come back to tasks list

28. Start process of calculation

31. This task does not have a responsible,
so we must claim this task

32. Add equation parameters

33. We have a solution

34. Check process with other parameters

38. Add parameters to get unknown
solution

39. We do not have a solution, so we
will check the variables

40. Discriminant is less than zero, so
there is no solution

41. We can set the responsible to each
task, so we do not need to claim
tasks

46. Task already owned

48. Train yourself 1

49. Set defaul variables for a,b,c in format:
${ a }

50. Add form to start Event and check process
running

51. Train yourself 2

52. 1. Remove form data from Start process,
but leave default variables in format ${a}
in UserTask. Start process by add some
variables — a, b, c

55. Add variables to process

56. 2. Try to start process without variables
3. Try to delete all the deployments from
Cockpit

57. Thanks for watching!
Svyatoslav Nadozirny 2020 (C)
Integration and processes