Cómo dibujar un diagrama BPMN

Write down the event that starts the process, then every distinct way it can finish. Not the steps - the ends. This takes two minutes and it is where the disagreements are.

"Recruiting" is not a process. "From an approved vacancy to a live advert" is: it has one trigger and a stated finish, so two people can now disagree about whether shortlisting is inside it, cheaply, before anything has been drawn.

Name more than one end event if the process has more than one outcome. A process that can be rejected and does not show rejection as an ending is a process the diagram is lying about.

Before any shapes, write the steps as a plain list, each one a verb and an object: write advert, review wording, post advert. The naming rule is doing work here rather than enforcing style.

• A noun on its own - Advert - hides whether it is written, checked or published.
• A passive form - Advert is reviewed - hides who reviews it, which is the question the pool has to answer later.
• A name containing and is two tasks, or it is a subprocess. Split it now, while it is a line of text rather than a box with four edges attached.

One pool, left to right, start event to end event, no gateways at all. This is the figure at the top of this article, and it should feel too simple - that is the point.

The happy path is the spine everything else hangs from, and drawing it alone forces the question of what normally happens to be settled before the question of what occasionally happens. Diagrams built the other way round tend to have three exception branches and no clear main line, which is how a process diagram ends up being read by nobody.

Keep it on one horizontal line. Bending the main path around a corner to fit the page costs a reader more than a wide diagram does.

Now ask, at each step, what else can happen. Every answer is a gateway, and the marker in it is the whole decision:

• Exactly one path - exclusive gateway, the rhombus with an X.
• All paths, always - parallel gateway, the plus. Remember the join waits for every branch.
• One or more, depending - inclusive gateway, the circle. Powerful and the easiest to deadlock, so balance every split with its join.
• Whichever happens first - event-based gateway. It decides nothing, it waits.

Then add the loops, because this is the step people skip. If work can be sent back, draw the flow back to the task that repeats - not to the gateway that noticed the problem. The full set of five rhombi and when each is right is in BPMN gateways.

A second pool is expensive: sequence flow may not cross a pool boundary, so everything between the two becomes a message, and the diagram gets taller. Pay that cost for one reason only - there is a participant you do not control and cannot instruct.

A customer, a supplier, a payment provider, a job board: those are pools. Your own departments are not. Finance and legal both work for the same organisation and sequence flow has to be able to run between them, so they are lanes inside one pool.

When you do add one, consider leaving it empty. A collapsed pool says the messages are known and the internals are not, which is usually the honest position and stays true when the other party changes how they work.

Quick, mechanical, and between them they catch most of what goes wrong:

1. Every path reaches an end event. Follow each branch with a finger. A path that stops at a task is a token stranded forever.
2. Every split has its join. Particularly parallel and inclusive ones - an unbalanced pair is the standard way to deadlock a process.
3. Every task is a verb and an object. The names that fail this are the steps nobody has thought through.
4. No sequence flow crosses a pool boundary. One glance along each boundary line.
5. Somebody who does the work has read it. This finds more defects than the other four together, and it is the only one that catches a diagram that is internally perfect and describes the wrong process.

Five complete processes built this way are in BPMN examples, and every symbol used along the way is indexed in the BPMN symbol reference.