Common Workflow Compositions

Understanding common workflow compositions helps you design better workflows and solve problems more effectively.

1. Fan-Out/Fan-In (Parallel Processing)

○ → [Prepare Data] → ◇+ → [Process A] → ◇+ → [Combine Results] → ●
                      └ → [Process B] → ┘

Use when: Processing the same data with multiple services simultaneously

Benefits:

• Faster execution (parallel instead of sequential)
• Independent processing paths
• Results synchronized automatically

Example: Execute a quantum circuit on multiple backends to compare results.

2. Pipeline (Sequential Processing)

○ → [Step 1] → [Step 2] → [Step 3] → [Step 4] → ●

Use when: Each step depends on the previous step's output

Benefits:

• Clear data flow
• Simple to understand and debug
• Each step transforms data for the next

Example: Generate circuit → Encode → Execute → Decode → Visualize

3. Conditional Flow (Exclusive Gateway)

○ → [Check Condition] → ◇× → [Path A] → ●
                         └→ [Path B] → ●

Use when: Different actions needed based on data or conditions

Benefits:

• Dynamic workflow behavior
• Handle different scenarios
• Optimize based on input characteristics

Example: Use fast optimization for small problems, accurate optimization for large problems.

Setting Conditions:

1. Add an Exclusive Gateway (◇×) from the palette
2. Create multiple outgoing paths
3. Select each sequence flow (arrow)
4. In properties, set Condition expression:

   = count(flightRoutes) < 5  // Fast path
   = count(flightRoutes) >= 5  // Accurate path

4. Error Handling with Boundary Events

○ → [Main Task] → [Success Action] → ●
    │
    └→ [Error Handler] → [Cleanup] → ●

Use when: You need to handle failures gracefully

Benefits:

• Graceful degradation
• User notification on errors
• Cleanup and recovery actions

Implementation:

1. Select a service task
2. Click Append Boundary Event → Error Boundary Event
3. Connect error event to error handling tasks
4. Add notification or cleanup services

5. Looping (Multi-Instance)

○ → [For Each Item in Array] → [Process Item] → [Collect Results] → ●

Use when: You need to process array data iteratively

Benefits:

• Process collections automatically
• Parallel or sequential execution
• Aggregate results

Implementation:

1. Select a service task
2. In properties, find Multi Instance
3. Set Loop Type: Parallel or Sequential
4. Set Input Collection: Array variable name
5. Set Element Variable: Name for current item

Example: Process each flight route individually for detailed analysis.

6. Timer Events (Scheduled Execution)

○ (clock icon) → [Periodic Task] → [Process Data] → ●

Use when: You need periodic or scheduled execution

Benefits:

• Automated scheduling
• Time-based triggers
• Periodic monitoring

Types:

• Timer Start Event: Trigger workflow on schedule
• Timer Intermediate Event: Wait for duration
• Timer Boundary Event: Timeout handling

Example: Run optimization every hour with latest flight data.

7. Message Events (External Triggers)

○ (envelope icon) → [Wait for Message] → [Process] → ●

Use when: Workflows triggered by external systems

Benefits:

• Event-driven architecture
• Integration with external systems
• Asynchronous communication

Use Cases:

• API webhooks
• External data updates
• User actions