Validate left-to-right straight happy path modeling

[till-stadtler]

The rule should detect the following modeling patterns

Users often do not follow the modeling best practicing rule "modeling from left to right": https://docs.camunda.io/docs/components/best-practices/modeling/creating-readable-process-models/#modeling-from-left-to-right
They often branch off, up or down, making it difficult to decipher the "happy path".

This rule checks if at least one start and end event have the same y-coordinate (height on the canvas) in every scope.
This rule should apply to operational models (executable checkbox ticked).

This is a violation:

(This is a very simple example. In complex process models, the end event of the happy path can be hundreds of pixels above or below the start event.)

Here, at least one end event has the same height as a start event:

How does the rule improve the BPMN diagram?

Users are reminded to model the happy path from left to right. (Link to documentation can be added)
Drives remodeling efforts and contemplation about a horizontal happy path.

Rule Details

• Name: modeling-from-left-to-right
• Default notification level: warn

What alternatives did you consider?

BPMN models continue to not follow the modeling best practice of modeling from left to right.
(Of course, users might place a non-happy path end event on the same height as a start event. Without marking an end event as "the happy path end event", we are unable to notice this. Also, the models can branch off along the happy path if we do not also check that there is a path with only horizontal sequence flows (all waypoints on the same y-coordinate) between a start and end event.)