Actions in MoSy represent the atomic interactions that actors perform within a system. They are the connected pieces of a Flow., defining how actors engage and progress toward achieving objectives.
Actions are crucial because they connect actors with system entities, metrics (defined later), and key objectives. They build the story that helps structure flows and ensures alignment between business intent and technical implementation. Thus, actions form the backbone of system behavior.
Some examples of actions in an e-commerce system are “Add product to cart” (Customer actor), “Validate Stock” (System actor), and “Process payment” (Payment partner actor).
Flows are composed of Actions
End-to-end flows in a system typically require actions from multiple actors. The MoSy framework portrays this by placing actors in different swimlanes. Actions are connected following a horizontal sequence that represents time. If you’re familiar with BPMN diagrams, you’ll recognize this pattern as they resemble lanes in a BPMN representation. One of the main differences is that MoSy is less strict and more straightforward. MoSy doesn’t focus on detailing the process.
Each flow in MoSy requires a dedicated diagram, so the first step is to use the name of the corresponding flow from the High-Level System View as a heading. Then, you’ll need a swimlane for each actor participating in the flow, including your system (which you can color in a slightly different tone). See the figure below for an example. Then, you add the sequence of actions, putting them in the corresponding swimlane and connecting them with arrows (some actions are omitted in the example for brevity).
When adding actions, you must identify and mark those that make an actor fulfill a key objective. Typically, this should happen in each flow for at least one of the actors and should drive the design of the rest of the actions in the flow. If you can’t find any action where an actor gets something they wanted, that flow doesn’t add value or make sense in the system. The only exception might occur when modeling supporting flows that can be used later to build other shorter flows on top (which deliver value). You can use sticky notes or text and emojis to flag those actions.
A first look at the MoSy’s Flow Diagram depicting Actions performed by Actors in swimlanes