# Boundary Events

**Boundary Events** are special event nodes that are attached to the **boundary of an activity** in the Process Template Diagram.\
They are used as **triggering events** that can interrupt or react to specific situations while an activity is being executed.

In ONEWEB **Process Designer**, Boundary Events follow **BPMN standards** and allow processes to respond dynamically to runtime conditions.

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### Purpose of Boundary Events

Boundary Events are used to:

* React to exceptional or time‑based conditions during task execution
* Interrupt an activity when a specific event occurs
* Trigger alternative execution paths without disrupting the overall process structure

They help model **real‑world exception handling and timing behavior** in business processes.

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### Types of Boundary Events

Process Designer provides **two types of Boundary Events**:

1. **Timer Boundary Event**
2. **Error Boundary Event**

Each type serves a different purpose and is described below.

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#### Timer Boundary Event

The **Timer Boundary Event** is used to trigger an action when a **time‑based condition** is met.

Typical use cases include:

* Task timeout handling
* Escalation when an activity takes too long
* Reminder or follow‑up actions after a defined duration
* Scheduled interruptions

Behavior:

* Attached to an activity
* Triggered when the defined time condition is reached
* Can either interrupt the activity or trigger an alternate flow (depending on configuration)

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#### Error Boundary Event

The **Error Boundary Event** is used to handle **runtime errors or exceptions** that occur during the execution of an activity.

Typical use cases include:

* Handling system or integration failures
* Capturing business errors from service calls
* Redirecting flow to error‑handling logic

Behavior:

* Attached to an activity
* Triggered when the activity throws a defined error
* Transfers execution to an alternate error‑handling path

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### Usage Guidelines

* Boundary Events must be **attached to an activity**
* Use Timer Boundary Events for **time‑based control**
* Use Error Boundary Events for **exception handling**
* Clearly design alternate paths to prevent dead‑ends
* Avoid excessive boundary events on a single activity to maintain clarity

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### Summary

**Boundary Events** enhance process flexibility and robustness by enabling **event‑driven reactions** during task execution.

Key points:

* Attached directly to activities
* React to timing or error conditions
* Support Timer and Error types
* Allow interruption or alternative flow execution
* Essential for modeling real‑world exceptions and deadlines

Proper use of Boundary Events ensures that processes designed in **ONEWEB Process Designer** are **resilient, responsive, and production‑ready**.


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