Given how workflows are done, it is possible to create several workflows attached to a same model. In my understanding that would allow to separate some activities and transitions that are independent to others and prevent the system checking all the possible transitions and conditions, but only those defined in a specific workflow.

However, the methods defined in the Workflow Service, like for instance trg_validate does only take in parameters the res_model and res_id. So how can it know on which workflow to look at ?

Let's say we want to delete the workinstance of a particular object by calling trg_delete. Will it delete all workinstances of all workflows ? If yes, then what is the point of having several workflows for a same model ?