Parallel and Conditional Flows Explained

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When you see a team pause mid-conversation to clarify whether a decision point uses AND or XOR, you know they’ve moved beyond copying templates. They’re thinking—truly thinking—about logic flow. That moment of clarity is where real mastery begins. It’s not about drawing shapes. It’s about understanding how decisions split and merge, and when each type of gateway applies.

My advice? Start with one rule: every decision must serve a purpose. Don’t add gateways just because they “look right.” Let every branching point answer a real question—what’s the condition? What happens if it’s true or false? That mindset transforms flow diagrams from artwork into actionable models.

Here, you’ll learn how to use BPMN gateway patterns to represent parallel and conditional flows with precision. You’ll see real examples, avoid common mistakes, and gain the confidence to model complex business logic—without overcomplicating it.

Understanding Gateway Types: AND, OR, and XOR

Gateways are the decision points of your BPMN diagram. They determine how control flows from one step to the next, based on conditions or triggers.

AND Gateway: When All Paths Must Execute

An AND gateway splits flow into two or more parallel branches. All branches must complete before the process can continue.

This is ideal for tasks that must occur simultaneously, like initiating a background check and sending a welcome email after a new hire onboards.

Use AND gateway when every condition must be true.
Common in parallel processing, approvals, or system triggers.
Always use the parallel flow BPMN pattern when multiple tasks start at once.

OR Gateway: When Any Path May Trigger

An OR gateway lets flow continue if any one condition is met. It’s less common and more complex because it requires careful handling of implicit or explicit conditions.

Use OR only when you’re explicitly modeling a choice where only one path should execute—like a customer choosing “refund” or “replace” in a support case.

OR gateways are not used for simple yes/no decisions.
They require clear, documented conditions to avoid ambiguity.
Best reserved for complex decision logic where exclusivity is intentional.

XOR Gateway: When Only One Path May Proceed

XOR stands for “exclusive.” Only one outgoing sequence flow can trigger, based on a condition. It’s the most common type for decision points.

Use XOR when you need a strict choice: “Is the customer active?” → Yes → Continue. No → Escalate.

Use XOR for every typical decision: yes/no, pass/fail, available/unavailable.
Always label the outgoing flow with the condition (e.g., “Yes” or “Customer Active”).
Never use XOR for parallel execution.

Mastering Sequence Flow BPMN: From Start to End

Sequence flow BPMN defines the order in which activities happen. It’s the backbone of your diagram.

Each flow starts at an event, activity, or gateway and connects to the next. But not all flows are equal—some are conditional, some are sequential.

Rules for Valid Sequence Flow

Sequence flow should always go from left to right or top to bottom for readability.
Never draw flows that cross without a clear junction point.
Every sequence flow must connect to a valid element (event, task, gateway).
Always use solid lines with arrowheads to represent flow.

Common Mistakes in Sequence Flow

Connecting a gateway directly to a task without a flow.
Using multiple gateways to split a task that should be sequential.
Forgetting to label conditions on XOR gateways.

When a flow feels tangled or hard to trace, ask: “Can someone new understand this in less than 30 seconds?” If not, simplify.

Practical Example: Onboarding a New Employee

Let’s walk through a real-life scenario using BPMN gateways.

Start event: “New Employee Hired”
Task: “Set up email and access”
AND gateway: Split flow into two parallel paths
Path 1: “Run background check”
Path 2: “Send welcome email”
Both paths converge at an AND gateway
Final task: “Assign onboarding buddy”
End event: “Onboarding Complete”

This example shows a clean parallel flow BPMN design. Both tasks run independently but must finish before the next step begins.

When to Use Which Gateway: Decision Tree

Choosing the right gateway isn’t guesswork. Use this decision tree to guide your design.

Question	Answer	Gateway Type
Do all branches need to complete before continuing?	Yes	AND
Do only one path need to execute?	Yes	XOR
Can multiple paths trigger, but not all?	Yes	OR (use with caution)
Is the decision based on a single true/false condition?	Yes	XOR

This table is your quick reference. Use it to check your gateways before finalizing your diagram.

Best Practices for BPMN Gateway Patterns

Even experienced modellers make small mistakes. Avoid these traps:

Never use AND gateways to model sequential logic. That’s what sequence flow is for.
Always label XOR conditions clearly. “Yes” or “No” is not enough—use “Customer Verified” or “Check Passed”.
Keep gateways at the intersection of flows—don’t place them in the middle of a long path.
Use swimlanes to assign responsibilities for each flow path.
Validate your model using Visual Paradigm’s built-in checker to catch unconnected flows or missing gateways.

Frequently Asked Questions

What’s the difference between AND and XOR gateways in BPMN?

AND gateways split flow into multiple branches that all must complete before continuing. XOR gateways allow only one outgoing path to execute based on a condition. Use AND for parallel work, XOR for exclusive choices.

Can I use BPMN conditional flow without a gateway?

No. Sequence flow BPMN only connects elements. Conditional logic requires a gateway to determine which flow to take. Without a gateway, the flow is always sequential.

Why use OR gateways if XOR is more common?

OR gateways are used when multiple conditions could apply and flow should continue if any is true. But they’re rare and risky—ambiguity can lead to incorrect execution. Use XOR or AND instead unless you have a clear need.

How do I model parallel flow BPMN in Visual Paradigm?

Use the AND gateway symbol. Drag the gateway after a task, then connect two or more outgoing flows to separate tasks. The model will auto-validate that both branches are connected to the same AND join point.

Do gateways always need to be followed by a task?

No. A gateway can connect to another gateway, event, or even a sub-process. But ensure the logic makes sense. For example, an AND split can lead to two OR gateways if the conditions are independent.

What happens if I forget to close a parallel flow BPMN?

If a process starts a parallel flow with an AND gateway but doesn’t have a matching AND join, the model is invalid. The workflow can’t proceed correctly, and tools like Visual Paradigm will flag it as an error. Always pair every AND split with an AND join.