Navigating BPMN Gateways: Making Sense of 69 Options

Picture yourself at a pivotal juncture – not just an ordinary crossroads, but the bustling intersection of Business Avenue and Process Street. Seated in the driver’s seat, you find yourself tasked with navigating through a labyrinth of intricate decisions and actions. It’s within this dynamic landscape of process modeling that the metaphorical crossroads truly come alive, shaped by the presence of Business Process Model and Notation (BPMN) gateways. Interestingly, these gateways share more similarities with road signs than one might initially perceive.

The BPMN Gateways Manual serves as your comprehensive guide through this intricate network. Within its pages, we aim to unravel the meaning, intricacies of placement, and the regulations associated with the 69 existing BPMN gateways:

This manual is your roadmap through the diverse and complex world of BPMN gateways, likening them to road signs that guide you through the multifaceted journey of process modeling. So, fasten your seatbelts as we embark on this exploration, providing you with the knowledge and insights needed to navigate the intersections of Business Avenue and Process Street with confidence.

Part 1. Frequently Used Gateways

1. Exclusive gateway

Notation:

An Exclusive Gateway is akin to a “T-junction” within your processes, marked by a distinct notation resembling an empty diamond shape or a diamond shape with a cross inside. It stands as a pivotal decision point where the path ahead diverges into multiple lanes, demanding that you choose just one. This gateway functions by posing a specific question related to the current state of your process. Your response to this question determines the path you will follow among the presented alternatives.

Example:

In the diagram, a day starts when your alarm clock goes off. You switch off the alarm clock and then choose your activities based on which day of the week it is:

• if it’s Saturday or Sunday, you keep sleeping until you feel hungry.
• if it’s a workday, you get up, brush your teeth, perform other activities to get ready for the day, and only then make breakfast.

Specifics of the Exclusive Gateway:

1. Lanes coming out from an Exclusive Gateway may or may not later converge (merge) back into one path. To pair or not to pair the gateway is rather a matter of taste and agreement within your team than a strict rule:

2. Which shape to use for the gateway – with a cross or without – is also a matter of taste and agreements within your team. But for consistency, it’s better to choose one option and stick to it.

2. Inclusive gateway

Notation:

An Inclusive Gateway also forks into multiple lanes, but unlike at an Exclusive Gateway, you can choose several paths to go. At the Inclusive Gateway, you pause and check out all the presented lanes and their conditions. If you realize that several conditions apply to your current state, you include all of them into your route.

Example:

Consider a scenario where your hunger prompts you to decide on a meal. At the Inclusive Gateway:

• If you desire a caffeine boost, you prepare a cup of coffee.
• If a craving from your favorite restaurant strikes, you opt for a delivery.
• If you recognize a need for a proper dose of veggies, you choose to make a salad.

You can choose one option exclusively, a combination of two options (such as coffee and delivery), or even opt for all three simultaneously. Subsequently, you wait until all selected options are ready, resulting in a meal that satisfies your varied preferences.

Specifics of the Inclusive Gateway:

1. Optionally, this gateway can have a default option (marked with \). This means that if no other path condition evaluates to true then the default path will automatically proceed. When a default path is not defined, and none of the path conditions evaluate to true, then a runtime exception occurs.

2. Like an Exclusive Gateway, an Inclusive Gateway can be or not be paired depending on how teams agree upon this aesthetic question. However, remember that an Exclusive Gateway can’t be paired with an Inclusive Gateway. The latter doesn’t include the lanes coming out from the first Exclusive Gateway:

3. Parallel gateway

Notation:

At a Parallel gateway, you don’t take any decisions. The gateway presents you with several flows that happen simultaneously as you’re moving through the process.

Example:

Consider the goal of becoming the most effective version of yourself. You decide to optimize your daily routine, transforming your meals into a synchronized experience. This approach allows you to not only nourish yourself but also gain valuable insights from a podcast and fulfill your daily step count goal—all happening simultaneously. So, now your breakfast, lunch, and dinner include 3 parallel activities:

In this scenario, the Parallel Gateway serves as the orchestrator of these parallel activities. Each activity is independent of the others, yet collectively they contribute to the overarching goal of self-optimization.

4. Complex gateway

Notation:

As the name suggests, a complex gateway is not intuitive. Therefore, it is always accompanied by some explanatory message, which simplifies the understanding of the gateway. The most common scenario when people use Complex Gateways is when they merge lanes from a Parallel Gateway under a particular condition.

Example:

In the case of a highly productive breakfast/lunch/dinner, how do we know that the meal is over and we can continue with other activities? We can merge the lanes from the Parallel Gateway into a Complex Gateway and say “When all the food is eaten and at least one of the two events (podcast is finished or 500 calories are burned on the treadmill) happened, we can consider the food break over.“

5. Exclusive Event-based gateway

Notation:

An Exclusive Event-Based gateway shares similarities with an Exclusive gateway in that you can choose only one out of several lanes forking from the gateway. However, the distinction lies in the timing of decision-making:

• At an Exclusive gateway, you can promptly make a decision regarding the current state of your system and choose the right path immediately.
• At an Exclusive Event-Based gateway, you are required to pause and wait until one of the events related to the forking lanes occurs before making a decision.

Example:

Consider a scenario where you find yourself at a restaurant, having just placed an order for a meal. At this Exclusive Event-Based gateway:

• If the meal arrives within 15 minutes, you decide to stay and enjoy your meal.
• However, if 15 minutes pass without any sign of your order, you make the decision to leave the place and express your dissatisfaction through a devastating review.

In this example, the Exclusive Event-Based gateway introduces a temporal aspect to decision-making. The choice you make is contingent upon the occurrence or non-occurrence of events within a specific time frame, emphasizing the importance of timing in determining your course of action.

6. Parallel Event-based gateway

Notation:

Like a Parallel gateway, a Parallel Event-based gateway doesn’t make you take any decisions. Multiple flows unfold concurrently, but in this case, each flow is contingent upon the occurrence of a specific event.

Example:

In the scenario of a highly productive meal, any of the three parallel subprocesses—consuming the food, listening to a podcast, and using a treadmill – can initiate first. Depending on which event transpires first – your meal is ready, the podcast is downloaded, or the treadmill is switched on, the corresponding action follows:

The sequence in which these parallel activities unfold doesn’t matter. What does matter is that any activity can start without the corresponding preliminary event having happened.

Part 2. Specific Event-based gateways

While Part 1 presented you with the must-know gateways to navigate any Business Process terrain, Part 2 is about rare Business Process road signs that you will hardly find in any available BPMN guidebook.

These unique gateways share a commonality – they are Event-Based, and beyond that, each is inseparably tied to a specific BPMN event. Unlike their more prevalent counterparts – Exclusive and Parallel Event-Based gateways, these gateways offer a nuanced approach to decision-making, often involving scenarios where the nature of the event holds the key to the chosen path.

Let’s revisit the Exclusive Event-Based gateway for a moment. This gateway allows us to make decisions based on the occurrence of events, emphasizing the freedom to choose the path based on whichever event happens first. Notably, the Exclusive Event-Based gateway accommodates diverse event types, such as Timer Events, Message Events, and more. It stands as a universal gateway, providing unparalleled flexibility in designing business processes.

On the other hand, specific Event-Based gateways imply that we know an event of which type (a Timer, Message etc.) is going to happen. It’s just the nature or specifics of the event determine which path to choose.

Example:

Envision managing your inbox as a curated experience. The process starts with receiving an email. If it’s promotional, a swift transfer to the Trash folder ends the interaction. For non-promotional emails, the process delves into a thoughtful dance: reading and categorizing into the Personal, Work, or For Later folder (the default folder in which you put all emails that you can’t categorize right away).

One way to depict this process in a diagram is the following:

And here is another way to depict the same process:

Let’s take a look at another example.

At one point of the process, an error occurs. Depending on the type of the error, the task to process it differs.

Essentially, when you encounter a BPMN event within a diamond shape that isn’t an Exclusive or Parallel Event-Based gateway, mentally breaking down the image into the event itself and the subsequent Exclusive Gateway is a practical approach.

Specific Event-based gateways are no more than a way to picture process divergence based on the details of a particular event, but instead of two elements, there is only one (economical use of chart space). Whether or not you utilise such a notation depends on your taste and agreements in your team/organization. If specific Event-Based gateways do not provide clarity and your stakeholders are more used to the classics, it’s better to stick to the traditional 6 gateways described in Part 1.

But regardless of the style you choose to depict specific Event-Based Gateways, in order to operate with them confidently, you need to be familiar with various categories of BPMN events such as:

• start/intermediate/end events
• catching/throwing events
• interrupting/non-interrupting events

and their combinations.

It’s another big chapter in the BPMN Traffic Manual, the mastering of which is a crucial step toward becoming a true professional on the road of Business Process Modeling.

Much like deciphering road signs while driving, understanding BPMN gateways can be remarkably intuitive. Observing one in a diagram often provides a clear indication of whether it signifies a decision-making point or a moment of process parallelization, contextualized within the schema. However, the significance of these gateways extends beyond mere interpretation; they are integral to both interpreting existing processes and constructing new ones, forming the backbone of a BPMN roadmap.

When you encounter a BPMN diagram, you’re not just reading signs that follow established processes; you’re also an architect, designing novel processes and encapsulating them within the visual language of BPMN. The challenge lies not only in recognizing the gateways but also in wielding them effectively to articulate complex business processes clearly and unambiguously.