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Swimlane diagrams – systems or actors or both?

We’ve been having some internal debate about the appropriate use of swimlane diagrams.  Everyone agrees that swimlane diagrams are a helpful model.  They allow you to create a process flow that does not require you to identify the system or actor involved in each process step, as this can be inferred from the swim lane in which that process step occurs.

Where we have some disagreement is in whether or not it is appropriate to mix systems with actors in a single diagram.  One side argues that swimlane diagrams should have either all actors or all systems, but not both.  The other side argues that mixing the two is entirely appropriate.

While I don’t expect to resolve this argument within this post, I thought I’d highlight a few thoughts about the two schools of thought.

Systems or Actors, but not both

  • This is cleaner than mixing, and it allows you to look at the actors involved in a task as a whole, since each actor has its own swimlane.
  • Clearly useful for modeling business processes that have no system component, or for representing the business process from a system agnostic standpoint
  • Also useful for mapping processes that are implemented by a collection of systems that have minimal human interaction.
  • You can always “mix” the model of actors vs systems by identifying actors or systems inside the process steps

Mix Actors and Systems Freely

  • Many business processes involve systems taking the role of a person (in fact, many systems are designed to eliminate a person having to do something), so you could argue that a system taking the role of a person should have a swimlane that is a peer to a person
  • Interactions between a human actor and a system in a process almost always trigger a use case, though it is not always easy to reference the use case from the diagram.
  • If we’re defining human system interactions, are there better models for us to be using than a swimlane diagram?

4 Responses to Swimlane diagrams – systems or actors or both?

  1. Randy November 15, 2017 at 4:02 pm #

    I am encountering this dilemma. I have a flow where an actor is “Entering a Transfer Order within System X” and I have a swimlane for system X as a result that states “Create a pick to the WH to transfer goods to contractor”. The user initiated the process by utilizing system x and as a result system x did something. To me, one is showing how the system is being used by the person and the other is showing the system functionality performed. If we want to replace system x, I would need to know what system x does within the business process to know that this functionality needs to be fulfilled by a new system.

  2. Manny Bonet November 29, 2017 at 1:33 pm #

    Before there were computer systems all work was done by humans therefore all swim lanes represented humans. Little by little computer systems have replaced humans in every task they can do thus is seems to me that making a distinction between system and actor is really a non issue. A more accurate representation is that when it comes to performing work that can be mapped by a process diagram both systems and humans are actors in a process. A philosopher would clearly identify this as an ontological issue.

  3. Manny Bonet November 29, 2017 at 1:53 pm #

    I inadvertently gave an incomplete answer, Godel would be proud. You mention human – system interactions as if though there is some conflict. Lets use a doorbell as a system the human actor presses the button on the doorbell system. the doorbell system actor closes the circuit and generates the current which triggers the buzzer. The problem occurs here when we want to say that the human actor rings the bell, but that is simply not true the human actor touches a button the system actor rings the bell. a distinction that some would argue is trivial but is actually the source of many problems in modeling. I am sure you are aware that modeling is a province of philosophy.

  4. Manny Bonet November 29, 2017 at 4:06 pm #

    I inadvertently gave an incomplete answer, Godel would be proud. You mention human – system interactions as if though there is some conflict. Lets use a doorbell as a system the human actor presses the button on the doorbell system. the doorbell system actor closes the circuit and generates the current which triggers the buzzer. The problem occurs here when we want to say that the human actor rings the bell, but that is simply not true the human actor touches a button the system actor rings the bell. a distinction that some would argue is trivial but is actually the source of many problems in modeling. I am sure you are aware that modeling is a province of philosophy.

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