A fork node splits a single flow into multiple concurrent flows in a modeling diagram.
Understanding Fork Nodes
A fork node is a fundamental element used in activity diagrams to represent parallel execution paths. Its primary function is to take a single incoming flow and divide it into two or more concurrent flows.
Key Characteristics
Here's a breakdown of the characteristics of a fork node:
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Single Input: A fork node has exactly one incoming activity edge or transition. This represents the single flow of execution entering the node.
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Multiple Outputs: It has multiple outgoing activity edges or transitions. Each outgoing edge represents a separate, concurrent flow of execution.
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Parallel Execution: After a flow reaches a fork node, all outgoing flows are initiated simultaneously (or as close to simultaneously as the system allows).
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No Data Transformation: The fork node itself doesn't modify the data or information passing through it. It simply duplicates the flow.
Fork Node vs. Join Node
It's helpful to understand fork nodes in relation to join nodes:
| Feature | Fork Node | Join Node |
|---|---|---|
| Function | Splits a flow into concurrent flows | Synchronizes concurrent flows into one flow |
| Input | One incoming edge | Multiple incoming edges |
| Output | Multiple outgoing edges | One outgoing edge |
| Concurrency | Introduces concurrency | Resolves concurrency |
Example
Imagine an online order processing system. After an order is received, a fork node could split the process into:
- Payment Processing: Verifying payment details.
- Inventory Check: Checking if the ordered items are in stock.
- Shipping Preparation: Preparing the order for shipment.
All three of these processes can happen concurrently after the order is received.
Use Cases
- Parallel Tasks: When multiple tasks can be performed independently and simultaneously.
- Concurrent Processes: Initiating several parallel processes within a larger system.
- Asynchronous Operations: Starting asynchronous operations that don't need to complete in a specific order.
