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Understanding Exclusive (XOR) Gateway

An exclusive gateway (also called XOR gateway) represents a decision point in your process where exactly one outgoing path is selected based on conditions. This is one of the most common routing mechanisms used in business process modeling.

Core principles of Exclusive Gateways

When designing decision logic with exclusive gateways, consider these guiding principles:

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Configuring an Exclusive Gateway node

To configure this node effectively, it’s essential to set up both the input and output sequences within the gateway process.

Exclusive Gateways single

Exclusive Gateways multiple

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General configuration

  • Node name: Give your node a meaningful name.
  • Can go back: Enabling this option allows users to revisit this step after completing it.

When a step has “Can Go Back” set to false, all preceding steps become inaccessible.

  • Stage : Assign a stage to the node.

Exclusive Node Config

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Gateway decisions

  • Language: When configuring conditions, you can use JavaScript, Python, MVEL, or Groovy expressions that evaluate to either true or false.
  • Conditions: In the Gateway Decisions tab, you can see that the conditions (if, else if, else) are already built-in and you can select the destination node when the condition is true.

The order of expressions matters; the first true evaluation stops execution, and the token moves to the selected node.

Exclusive Gateway Decisions

After the exclusive portion of the process, where one path is chosen over another, you’ll need to either end each path (as in the example below) or reunite them into a single process (as in the example above) using a new exclusive gateway without any specific configuration.

Exclusive Gateways Multiple Flows

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JavaScript examples

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Getting input from a Switch UI element

Let’s consider the following example: we want to create a process that displays 2 screens and one modal. The gateway will direct the token down a path based on whether a switch element (in our case, VAT) is toggled to true or false.

Exclusive Gateway JavaScript Example

If, during the second screen, the VAT switch is toggled on, the token will follow the second path, displaying a modal.

After interacting with the modal, the token will return to the main path, and the process will continue its primary flow.

Example configuration:

  • Language: JavaScript
  • Expression:
input.application.company.vat == true // you can use the same method to access a value for other supported scripts in our platform: MVEL, Python and Groovy

Essentially, you are accessing a specific value or property within a structured data object. The format is usually input.{{key from where you want to access a value}}. In simpler terms, it’s a way to verify if a particular property within your input data structure (input.application.company.vat key attached to Switch UI element) is set to the value true. If it is, the condition is met and returns true; otherwise, it returns false.

The application.company.vat key corresponds to the switch UI element.

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Getting input from multiple UI elements

Consider another scenario in which the process relies on user-provided information, such as age and membership status, to determine eligibility for a discount. This decision-making process utilizes multiple conditions, and depending on the input, it may either conclude or continue with other flows.

Configuration example:

Exclusive Gateway JavaScript Example

In our case, the expressions fields will be populated with the input.application.client.age and input.application.client.membership keys, which correspond to the user input collected on the initial screen.

Here’s how we’ve configured the rules for our discount eligibility process:

  1. Users under 18 with standard membership are not eligible (redirected to not_eligible_modal):

    input.application.client.age < 18 && input.application.client.membership == "standard"

  2. Users 18 or older with standard membership are not eligible due to membership level (redirected to not_eligible_membership):

    input.application.client.age >= 18 && input.application.client.membership == "standard"

  3. Users 18 or older with gold membership qualify for a discount (redirected to discount_applied):

    input.application.client.age >= 18 && input.application.client.membership == "gold"

  4. Users 18 or older with platinum membership also qualify for a discount (redirected to discount_applied):

    input.application.client.age >= 18 && input.application.client.membership == "platinum"

  5. Any other combinations are sent to needsValidation for further review.

Each rule uses the logical AND operator (&&) to ensure both conditions must be true for the rule to apply. The rules are evaluated in sequence, and the process follows the path of the first matching rule.

The process is visualized as follows: