tomevault-io Dependency Mapping Skill
Map dependencies between implementation slices using Design Structure Matrix (DSM), calculate risk scores, and recommend implementation sequence.
When to Use
- During Ask mode Phase 2 (CONVERGE)
- When planning multi-slice features
- Before phasing to understand risk order
Instructions
Phase 1: Build DSM Matrix
Create a square matrix with slices on both axes. Mark dependencies with *:
| #1.1 | #1.2 | #2.1 | #2.2 | #2.3 | #3.1 |
---------+------+------+------+------+------+------+
#1.1 | - | | | | | |
#1.2 | * | - | | | | |
#2.1 | | * | - | | | |
#2.2 | | | * | - | | * |
#2.3 | | * | * | | - | |
#3.1 | | | | | | - |
Legend: * = row depends on column
Reading: Row #2.2 has * in columns #2.1 and #3.1 = #2.2 depends on #2.1 AND #3.1
Phase 2: Calculate Dependency Score
For each slice, count:
| Metric | Formula | Meaning |
|---|---|---|
| Fan-in | How many slices depend ON this? | High = blocker, ship early |
| Fan-out | How many slices does this DEPEND on? | High = risky, ship later |
| Dependency Score | Fan-out count | Lower = safer |
Phase 3: Calculate Leverage Score
Score each slice on reuse of existing patterns:
| Level | Score | Description |
|---|---|---|
| Full Reuse | 0 | Uses existing component from design system/Storybook as-is |
| Extend | 1 | Extends existing component with new props/variants |
| Compose | 2 | Composes multiple existing components |
| New Pattern | 3 | Creates new component following design system tokens |
| New System | 5 | Requires new patterns not in design system |
Check these sources before scoring:
/docs/design-system/components.md- Existing componentsGlob **/*.stories.tsx- Storybook patternsSemanticSearchfor similar implementations in codebase
Phase 4: Calculate Risk Score
Risk Score = (Dependencies x 2) + Leverage + PriorityTier
Where PriorityTier:
- P1 (Frontend-only) = 0
- P2 (Frontend + Backend non-breaking) = 1
- P3 (Backend contract changes) = 2
- P4 (Data model changes) = 3
Phase 5: Identify Blockers
Flag slices that block others (high fan-in):
#3.1 WorkspaceInvite Entity
Fan-in: 3 (blocks #2.2, #2.3, #2.4)
RECOMMENDATION: Consider stub/mock for Phase 1, or ship early despite risk
Phase 6: Rank by Risk
Sort slices by Risk Score (lowest first = ships first):
| Rank | Slice | Deps | Leverage | Tier | Risk Score |
|---|---|---|---|---|---|
| 1 | #1.1 Workspace Switcher | 0 | Extend (1) | P1 (0) | 1 |
| 2 | #1.2 Members Page UI | 1 | Compose (2) | P1 (0) | 4 |
| 3 | #2.1 List Members API | 1 | N/A | P2 (1) | 4 |
Output Format
## Dependency Analysis
### DSM Matrix
[Matrix as shown above]
### Risk Scoring
| Slice | Deps | Leverage | Tier | Risk | Rank |
|-------|------|----------|------|------|------|
| [Slice] | [N] | [Level (score)] | P[N] | [Score] | [#] |
### Blockers Identified
| Slice | Blocks | Fan-in | Recommendation |
|-------|--------|--------|----------------|
| [Slice] | [List] | [N] | [Stub/Ship early/etc] |
### Recommended Sequence
1. [Lowest risk slice] - [Why safe]
2. [Next slice] - [Dependencies satisfied by #1]
...
### Existing System Leverage
| Component | Source | Slices Using | LOC Saved |
|-----------|--------|--------------|-----------|
| [Component] | [design-system/Storybook] | [List] | ~[N] |
Invocation
Invoke manually with "use dependency-mapping skill" or follow Ask mode Phase 2 (CONVERGE) which references this skill.
Related Skills
phasing- Uses risk scores to group into phasesdesign-context- Identifies existing patterns to leveragegtm-alignment- May override risk-based order for GTM priority
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