Decompose Work Packages (Level 2)

Purpose

At Level 1 (EST-03) you sized features by T-shirt. That was good enough for a rough cut. Level 2 is different: you have the scenario, you have the screen, you have SAO.md describing exactly how the stack works. You don't need to guess which layers a feature touches — BPE-01 will tell you. EST-06 runs BPE-01 in dry-run/estimation mode on each work package to produce a bottom-up artifact list, then wraps each artifact with a PERT triplet from the Reference Table.

This is the key idea: BPE-01 Plan → exact artifact list → PERT triplets per artifact → sum = Function Point decomposition. No generic taxonomy lookup required.

Prerequisites

• docs/architecture/SAO.md exists and is current
• EST-05 complete (Rough Estimates available as cross-check)
• Requirements stability ≥ 80% (McConnell prerequisite)

Gating Condition

If SAO.MD does not exist, skip this activity. Return here after SAO.MD is produced (typically after ESM workflow completes). Record this as a gate condition in ESTIMATION_STRATEGY.md.

Steps

Step 1: Select the Work Package

Take the next undecomposed work package from the sprint plan (EST-05 output). You need three inputs:

1. The scenario file — docs/features/{act}/{feature}.feature
2. The screen — find the matching node in the dialogue map (docs/architecture/screen-flow.drawio)
3. SAO.md — the authoritative architecture and stack description

Step 2: Run BPE-01 in Estimation Mode

Execute BPE-01 (Plan Feature) for this work package, treating it as if starting from scratch. BPE-01 will produce an Implementation Plan that lists every artifact needed:

→ Input:  feature file + screen name + SAO.md
→ Output: Implementation Plan listing every artifact:
          - Django Model + Admin (if new data shape)
          - Repository methods (which ones, for what queries)
          - Service layer (what business logic)
          - Django View + URL pattern (which views, GET/POST)
          - Unit + Integration tests (what to test)
          - Django Template + HTMX (which fragments/pages)
          - Feature Acceptance Tests (from scenario steps)
          - Journey Certification Tests (if cross-feature flow)
          - DoD checklist
          - E2E Playwright tests + PR

For each artifact, BPE-01 will also output its reuse flag based on codebase assessment:
- NEW — doesn't exist yet, build from scratch
- EXTEND — exists but needs significant modification
- REUSE — exists, minimal touch needed

Estimation mode means: produce the plan but do not write any code. Stop after BPE-01 Plan and record the artifact list.

Step 3: Assign PERT Triplets

For each artifact in the Implementation Plan, assign PERT triplets (min / expected / max tokens) from the Reference Table K ranges:

Apply reuse multipliers based on BPE-01 codebase assessment:
- NEW: 1.0× (full token range)
- EXTEND: 0.6× (reading + modifying existing code)
- REUSE: 0.3× (trivial wiring or config change)

Step 4: Record the Work Package

Enter in the WBS Features tab:

Scenario ID:    {ACT}-{ENTITY}-{OPERATION}-{NN}
Feature:        {Feature name from .feature file}
Screen:         {Screen name from dialogue map}
Sprint:         {Sprint number}
L1 Size:        M (2 SP)
BPE-01 run:     YES / ESTIMATION MODE

Artifacts from BPE-01 Plan:
  WP-01  Django Model (Widget)           NEW     min=12K  exp=16K  max=25K
  WP-02  Repository (WidgetRepo)         NEW     min=8K   exp=11K  max=18K
  WP-03  Service (WidgetService)         EXTEND  min=8K   exp=11K  max=19K  [×0.6]
  WP-04  View + URL                      NEW     min=10K  exp=14K  max=22K
  WP-05  Unit + Integration Tests        NEW     min=16K  exp=22K  max=38K
  WP-06  Template + HTMX                 REUSE   min=2K   exp=4K   max=8K   [×0.3]
  WP-07  Feature Acceptance Test         NEW     min=10K  exp=14K  max=22K
  WP-08  DoD checklist                   NEW     min=4K   exp=6K   max=10K
  WP-09  E2E test + PR                   NEW     min=8K   exp=11K  max=18K
  ────────────────────────────────────────────────────────────────────────
  TOTAL:                                          min=78K  exp=109K max=180K

Step 5: Cross-Check Against Level 1 Rough Estimate

Compare Level 2 total to Level 1 estimate from EST-05:
- Within ±30% → consistent, proceed
- L2 > 30% higher than L1 → which artifact is driving the gap? Document it.
- L2 > 30% lower than L1 → check for missing artifacts. Common omissions: tests, DoD, E2E.

Record delta and rationale in the WBS Features tab notes column.

Step 6: Repeat for All Work Packages

Work through all sprint work packages, highest priority first. After every sprint's worth, sum L2 totals and compare against the Monte Carlo seed in EST-07. If cumulative L2 is >25% outside L1 project total, update the Rough Estimates tab before proceeding.

Rules to Follow

I. BPE-01 Is the Decomposition Engine

Do not substitute a generic artifact checklist for BPE-01 Plan. The whole point of Level 2 is that you have the actual feature, screen, and architecture — use them. BPE-01 will produce a more accurate artifact list than any template can.

II. DoD Is Fixed Overhead

The DoD checklist (BPE-06) applies to every work package. Never omit it. It is not optional.

III. Tests Are Not Optional

Unit, integration, feature acceptance, and E2E tests are separate work packages. Omitting them produces a false low — the work still happens, it just becomes unplanned rework.

IV. Decompose Before Estimating

Assigning a PERT triplet to a scenario as a whole without running BPE-01 first is a Level 1 estimate masquerading as Level 2. If you skip the BPE-01 step, mark confidence as LOW and document why.

V. Reuse Is Not Free

Extending an existing component still consumes tokens for reading, understanding, and modifying existing code. Use 0.3× for trivial reuse, 0.6× for significant extension, 1.0× for new.

Success Criteria

• BPE-01 Plan executed (estimation mode) for every Level 2 work package
• Each work package has a full artifact list with reuse flags
• PERT triplets assigned to every artifact
• L1/L2 cross-check performed and delta documented
• WBS Features and Detailed Estimates tabs complete

Inputs

Read these before starting this activity. They are produced earlier in the playbook and are authoritative — raise a drift event instead of deviating.

• User Journey (Document, Required) — produced by Define User Journey (#36).
• Screen Flow / Dialogue Map (Diagram, Required) — produced by Create Dialogue Maps (#38).
• Feature Files (Document, Required) — produced by Write Feature Files (#39).
• HTML Mockups (Code, Optional) — produced by Create Mockups (#40).
• Estimation Reference Table (Document, Required) — produced by Calibrate Reference Stories (#67).
• Estimation Template (Excel) (Document, Required) — produced by Size Scenarios (Level 1 SWAG) (#68).