Event-Based Gateway

Waits for the first of several competing events (messages, signals, timers) and routes to its path. All other subscriptions are cancelled when the first event fires.

<eventBasedGateway id="waitForResponse" />
<sequenceFlow sourceRef="waitForResponse" targetRef="msgCatch" />
<sequenceFlow sourceRef="waitForResponse" targetRef="timerCatch" />
 
<intermediateCatchEvent id="msgCatch">
  <messageEventDefinition messageRef="ResponseMessage" />
</intermediateCatchEvent>
<intermediateCatchEvent id="timerCatch">
  <timerEventDefinition><timeDuration>PT10M</timeDuration></timerEventDefinition>
</intermediateCatchEvent>

Execution behavior

1. The engine forks a token to each outgoing catch event and creates subscriptions for all of them, grouped by a shared event_gateway_group_id
2. When the first event fires, the server:
   • Marks that subscription as consumed
   • Deletes or marks all sibling subscriptions in the same group as consumed
   • Cancels any sibling timers
3. Execution continues only down the path of the winning event

The XOR enforcement is server-side — the engine itself creates all subscriptions; the server cancels the losers.

Supported target event types

• Message intermediate catch event
• Signal intermediate catch event
• Timer intermediate catch event