Task Decomposition
Complex tasks often fail because they're too big. Decomposition breaks them into smaller, manageable subtasks that AI can handle reliably.
The Problem with Complex Prompts
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Decomposition Strategies
There are two main ways to split a big task. The right one depends on whether the subtasks depend on each other.
Horizontal vs vertical decomposition
| Criteria | Horizontal (parallel) | Vertical (sequential) |
|---|---|---|
| How subtasks relate | Independent: each can run on its own | Dependent: each builds on the previous one |
| Order | Any order, or all at once | Fixed order, one after another |
| Best for | Gathering separate pieces, like sections of a report | Pipelines where each step needs the last step's output |
| Example | Write the summary, market analysis, and product description | Define requirements, then design, then build, then test |
Horizontal (parallel)
- How subtasks relate
- Independent: each can run on its own
- Order
- Any order, or all at once
- Best for
- Gathering separate pieces, like sections of a report
- Example
- Write the summary, market analysis, and product description
Vertical (sequential)
- How subtasks relate
- Dependent: each builds on the previous one
- Order
- Fixed order, one after another
- Best for
- Pipelines where each step needs the last step's output
- Example
- Define requirements, then design, then build, then test
Horizontal (Parallel Subtasks)
Main task: Write a business plan
Subtasks (can be done independently):
1. Write executive summary
2. Research market analysis
3. Analyze competitors
4. Describe the product
5. Plan marketing strategy
Vertical (Sequential Dependencies)
Main task: Develop a feature
Subtasks (must be sequential):
1. Define requirements
2. Design architecture (needs #1)
3. Write code (needs #2)
4. Create tests (needs #3)
5. Document feature (needs #3)
Exercise: Decompose a Complex Task
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Subtask Prompt Design
Each subtask should be:
- Focused - One clear objective
- Complete - Contains all needed context
- Independent - Minimal dependencies when possible
- Verifiable - Clear success criteria
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Combining Results
After decomposition, you need integration:
Final Prompt:
"I've completed these analyses:
[Market summary]
[Competitive analysis]
[Product description]
Now synthesize into a cohesive executive summary that ties together these insights. Maximum 300 words."
Exercise: Design a Decomposition Flow
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When to Decompose
Decompose when:
- Task has multiple distinct parts
- Output would exceed quality limits
- Different parts need different expertise
- Results need to be consistent across sections
Don't decompose when:
- Task is simple and focused
- Parts are highly interdependent
- Overhead of combining outweighs benefits
Practice: Decomposition Planning
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Decomposition turns impossible tasks into achievable workflows.