Implementation Approach

Implementation Strategy Selection Framework (Meta-cognitive Approach)

Meta-cognitive Strategy Selection Process

Phase 1: Decision-Sufficient Current State Analysis

Core Question: "What does the existing implementation look like?"

Analysis Framework

Architecture Analysis: Responsibility separation, data flow, dependencies, technical debt
Implementation Quality Assessment: Code quality, test coverage, performance, security
Historical Context Understanding: Current form rationale, past decision validity, constraint changes, requirement evolution

Meta-cognitive Question List

• What is the true responsibility of this implementation?
• Which parts are business essence and which derive from technical constraints?
• What dependencies or implicit preconditions are unclear from the code?
• What benefits and constraints does the current design bring?

Stop when another current-state fact cannot change responsibility, reuse, option validity, total complexity, a contract, or verification.

Completion evidence: inspected paths, observed architecture/data-flow facts, known constraints, inferred historical rationale labeled as inferred, and unknowns that could change strategy selection.

Transition: proceed when every strategy-relevant claim is observed, explicitly inferred with evidence, or recorded as unknown.

Phase 2: Design Convergence

Core Question: "What is the smallest design that delivers the current required outcome, and what evidence forces each addition beyond it?"

Complete these steps in order before exploring implementation strategies:

1. Existing-Surface Baseline: Form the simplest end-to-end path that delivers the current outcome through existing responsibilities. Explicit requirements and accepted decisions are binding; suggested mechanisms remain candidates.
2. Evidence Check: Test that path against current requirements, verified constraints, observed in-scope problems, and evidence-backed material risks. Keep only the unmet conditions that can change the selected design.
3. Targeted Comparison: For each unmet condition, test reuse, derivation from existing data, on-demand computation, or responsibility at the current caller or boundary before adding design surface. Compare viable choices by total complexity across the dimensions that materially differ: user decisions, settings, modes, concepts, outputs, persistent state, implementation paths, UX, runtime, implementation, testing, documentation, and maintenance. Select the lowest-total-complexity choice that satisfies the condition.
4. Subtraction Check: Remove each proposed addition and re-test its governing condition. Retain it only when the confirmed outcome, a required boundary, or necessary proof becomes unmet.

Candidate paths and rejected additions remain active analysis. The durable output is the Selected Design: the complete chosen path plus evidence for each added design surface and the condition that fails when it is removed. Only an accepted ADR may retain alternatives as decision history. During implementation, use the same convergence check without producing a separate artifact.

Completion evidence: one complete Selected Design; every added design surface names its current evidence, why lower-surface resolutions fail, and its subtraction result.

Transition: proceed when every supporting claim is observed, explicitly inferred with evidence, or recorded as unknown; route an unknown that blocks the next step as an exact evidence prerequisite. User interaction is required only when the unknown requires changing the confirmed outcome, desired-future requirements, or non-goals, or authorizing an irreversible action.

Phase 3: Strategy Exploration and Creation

Core Question: "When determining before -> after, what implementation patterns or strategies should be referenced?"

Strategy Discovery Process

Research and Exploration: repository patterns first; then official documentation for the resolved dependency version; then maintained OSS implementations; use literature/blogs only for supplementary alternatives and label them as non-authoritative
Creative Thinking: Strategy combinations, constraint-based design, phase division, extension point design

Reference Strategy Patterns (Creative Combinations Encouraged)

Legacy Handling Strategies:

• Strangler Pattern: Gradual migration through phased replacement
• Facade Pattern: Complexity hiding through unified interface
• Adapter Pattern: Bridge with existing systems

New Development Strategies:

• Feature-driven Development: Vertical implementation prioritizing user value
• Foundation-driven Development: Foundation-first construction prioritizing stability
• Risk-driven Development: Prioritize addressing maximum risk elements

Integration/Migration Strategies:

• Proxy Pattern: Transparent feature extension
• Decorator Pattern: Phased enhancement of existing features
• Bridge Pattern: Flexibility through abstraction

Completion evidence: at least two feasible candidate approaches when the decision is non-trivial, with each candidate mapped to the observed constraints it satisfies and the constraints it leaves unresolved.

Transition: proceed when candidates are comparable against the same constraint set.

Phase 4: Risk Assessment and Control

Core Question: "What risks arise when applying this to the existing implementation, and which control measurably reduces likelihood or impact while preserving verification and rollback?"

Risk Analysis Matrix

Technical Risks: System impact, data consistency, performance degradation, integration complexity
Operational Risks: Service availability, deployment downtime, process changes, rollback procedures
Project Risks: Schedule delays, learning costs, quality achievement, team coordination

Risk Control Strategies

Preventive Measures: Phased migration, parallel operation verification, integration/regression tests, monitoring setup
Incident Response: Rollback procedures, log/metrics preparation, communication system, service continuation procedures

Completion evidence: each material risk has likelihood/impact evidence, one preventive or containment control, and a verification point.

Transition: proceed when every high-impact risk has either a control or a blocking escalation.

Phase 5: Constraint Compatibility Verification

Core Question: "What are this project's constraints?"

Constraint Checklist

Technical Constraints: Library compatibility, resource capacity, mandatory requirements, numerical targets
Temporal Constraints: Deadlines/priorities, dependencies, milestones, learning periods
Resource Constraints: Team/skills, work hours/systems, budget, external contracts
Business Constraints: Market launch timing, customer impact, regulatory compliance

Completion evidence: each constraint is observed, inferred, or unknown; every unknown that can invalidate a candidate names the exact evidence prerequisite.

Transition: proceed when remaining unknowns cannot change the valid candidate set, or the user resolves them.

Phase 6: Implementation Approach Decision

Select the approach that satisfies all hard constraints and current requirements with the lowest transition risk and smallest verification delay. Use lifecycle cost and implementation effort only as tiebreakers after requirement coverage, compatibility, and risk control are equal.

Vertical Slice (Feature-driven)

Characteristics: Vertical implementation across all layers by feature unit Application Conditions: Low inter-feature dependencies, output in user-usable form, changes needed across all architecture layers Verification Method: End-user value delivery at each feature completion