Software Efficiency Ecosystem: A Matrix Approach to Specifications

Executive Summary

As the Green Software Foundation expands its specification portfolio across multiple domains (AI, Web, Mobile) and impact metrics (Energy, Carbon, Water, Abiotic Depletion), we face a combinatorial explosion problem. Each new domain requires updating every impact specification, and each new impact metric requires versions for every domain.

This proposal introduces a matrix architecture that separates domain specifications from impact specifications, enabling:

• Scalability: New domains automatically inherit all impact methodologies; new impact metrics automatically apply to all domains
• Reduced maintenance overhead: Update domain definitions once, or impact methodologies once, instead of maintaining N×M separate specifications
• Clear separation of concerns: Domain experts focus on software boundaries and functional units; impact experts focus on measurement methodologies
• Natural progression paths: Organizations can mature from operational metrics (SEE, SWE) to comprehensive metrics (SCI, SWI) without feeling like they've "failed" a specification
• Audience alignment: Each specification serves distinct stakeholders with different needs and agency

The Problem: Combinatorial Explosion

Current State

Today, as we deploy specifications across domains and impacts, we're creating a maintenance challenge:

• SCI exists as the foundational spec
• SCI for AI is being deployed
• SEE (Software Energy Efficiency) is being explored
• SWE (Software Water Efficiency) is being explored

The Explosion Pattern

As we scale:

1. Adding a new domain (e.g., Quantum Computing) requires updating every impact specification:

   • SCI for Quantum
   • SEE for Quantum
   • SWE for Quantum
   • SCE for Quantum
   • etc.

2. Adding a new impact (e.g., Abiotic Depletion) requires creating versions for every domain:

   • SAD for AI
   • SAD for Web
   • SAD for Mobile
   • etc.

3. Updating domain guidance (e.g., refining the functional unit for AI) requires changes across:

   • SCI for AI
   • SEE for AI
   • SWE for AI
   • Every other AI-related spec

This creates N×M specifications where N = number of domains and M = number of impact metrics.

Why This Matters

The combinatorial explosion creates:

• High maintenance burden: Every domain refinement cascades across all impact specs
• Inconsistency risk: Domain definitions may drift across different impact specifications
• Delayed value: New impact methodologies can't leverage existing domain work without creating multiple spec versions
• Cognitive overhead: Practitioners must navigate many similar-but-different specifications

The Solution: Matrix Architecture

Core Concept

Separate specifications into two orthogonal dimensions:

1. Software Domain Specification (SD): Defines software boundaries and functional units for different domains (AI, Web, Mobile, etc.) - NOT the impact being measured
2. Software Impact Specifications (SEE, SCE, SCI, SWE, SWI, SAD): Define measurement methodologies and equations for different impacts - NOT domain-specific boundaries

All measurements follow the pattern: X per R where:

• X = the impact metric (defined by Impact Specs)
• R = the functional unit (defined by Domain Specs)

The Matrix

| Domain ⌄ | SEE | SCE | SCI | SWE | SWI | SAD |
|----------|-----|-----|-----|-----|-----|-----|
| AI       |  ✓  |  ✓  |  ✓  |  ✓  |  ✓  |  ✓  |
| Web      |  ✓  |  ✓  |  ✓  |  ✓  |  ✓  |  ✓  |
| Mobile   |  ✓  |  ✓  |  ✓  |  ✓  |  ✓  |  ✓  |
| Quantum  |  ✓  |  ✓  |  ✓  |  ✓  |  ✓  |  ✓  |

Each cell represents a specific persona and audience with distinct needs and agency.

Example: Adding Quantum Computing

Today: Create 6+ new specifications (SCI for Quantum, SEE for Quantum, SWE for Quantum, etc.)

With Matrix: Update Software Domain Spec with one new section defining:

• Software boundary for quantum systems
• Recommended functional unit (e.g., per quantum gate operation, per circuit execution)

Result: All impact specifications (SEE, SCE, SCI, SWE, SWI, SAD) automatically support Quantum domain.

Example: Adding Water Efficiency

Today: Create versions for every domain (SWE for AI, SWE for Web, SWE for Mobile, etc.)

With Matrix: Create one SWE specification defining:

• Methodology for operational water measurement
• Equation for water per functional unit
• Data sources and calculation guidance

Result: SWE automatically works with all domains (AI, Web, Mobile, Quantum) using their established functional units.

Specification Definitions

Software Domain Specification (SD)

A single specification defining software boundaries and functional units for different domains:

• AI: Boundary = inference/training systems; Functional unit = per token, per prediction, per training run
• Web: Boundary = application services; Functional unit = per request, per user session, per page view
• Mobile: Boundary = client applications; Functional unit = per active user, per session, per transaction
• Quantum (future): Boundary = quantum circuits; Functional unit = per gate operation, per circuit execution

Key principle: The functional unit and boundary don't change across different impact methodologies. If you recommend "per token" for AI in SEE, you recommend "per token" for AI in SWE.

Software Impact Specifications

Each specification defines only the measurement methodology and equation:

SEE (Software Energy Efficiency)

• Metric: Operational energy per functional unit
• Scope: Direct energy consumption (Scope 1 & 2 equivalent)
• Audience: Engineering teams, DevOps, platform engineers

SCE (Software Carbon Efficiency)

• Metric: Operational carbon emissions per functional unit
• Scope: Energy + grid carbon intensity (Scope 2 equivalent)
• Audience: Sustainability teams, engineering teams, corporate reporting

SCI (Software Carbon Intensity)

• Metric: Operational + embodied carbon per functional unit
• Scope: Energy + grid carbon + embodied emissions (Scope 3 equivalent)
• Audience: Sustainability leaders, executive reporting, public disclosure

SWE (Software Water Efficiency)

• Metric: Operational water consumption per functional unit
• Scope: Direct/site-based water usage
• Audience: Data center operators, cloud providers, sustainability teams

SWI (Software Water Intensity)

• Metric: Operational + embodied water per functional unit
• Scope: Direct + indirect water usage (full supply chain)
• Audience: Policy makers, corporate water stewardship programs

SAD (Software Abiotic Depletion)

• Metric: Abiotic resource depletion per functional unit
• Scope: Mineral and metal resource consumption
• Audience: Circular economy teams, supply chain sustainability, academic researchers

Hierarchy and Dependencies

To avoid redundant information and ensure consistency, specifications inherit from upstream dependencies:

graph TD
    SD[Software Domain Spec]
    SD --> SEE[SEE: Operational Energy]
    SEE --> SWE[SWE: Operational Water]
    SWE --> SWI[SWI: Operational + Embodied Water]
    SEE --> SCE[SCE: Operational Carbon]
    SCE --> SCI[SCI: Operational + Embodied Carbon]
    SD --> SADE[SADE: Operational Abiotic Depletion]
    SADE --> SADI[SADI: Operational + Embodied Abiotic Depletion]

Dependency rationale:

• SCE depends on SEE: Carbon = Energy × Grid Carbon Intensity, so carbon methodology builds on energy methodology
• SCI depends on SCE: Total carbon = Operational carbon (SCE) + Embodied carbon
• SWE depends on SEE: Water and energy are often coupled (cooling, power generation)
• SWI depends on SWE: Total water = Operational water (SWE) + Embodied water

Taxonomy: Efficiency vs. Intensity

The naming convention signals measurement scope and organizational maturity:

Efficiency = Operational Focus

• Measures direct, operational impacts
• Examples: SEE, SWE, SADE
• Easier to measure with available data
• Aligns with Scope 1 & 2 reporting
• Entry point for organizations beginning their measurement journey

Intensity = Operational + Embodied

• Measures total lifecycle impacts
• Examples: SCI, SWI, SADI
• Requires supply chain data and embodied calculations
• Aligns with Scope 3 reporting
• Maturity milestone for advanced organizations

Rationale

This taxonomy reflects natural organizational progression:

1. Start with operational (Efficiency): Data is available, measurements are actionable at granular levels
2. Add embodied (Intensity): As organizations mature their reporting and supply chain transparency

Historical note: In 4 years of SCI development, we've learned that embodied emissions data isn't available at granular enough levels to be immediately useful to software teams. Operational metrics (SEE, SWE) provide stepping stones toward comprehensive measurement (SCI, SWI).

Organizations are encouraged to:

• Publish all levels: SEE, SCE, and SCI serve different audiences
• Progress over perfection: Celebrate operational metrics rather than viewing them as "incomplete" comprehensive metrics

Maturity Pathways

The hierarchy enables clear progression paths for organizations:

Maturity Levels

Level 1: Energy Foundation

• Measure SEE (operational energy)
• Build measurement infrastructure
• Establish functional unit definitions
• Outcome: Understand energy consumption patterns

Level 2: Carbon Accounting

• Measure SCE (operational carbon)
• Add grid carbon intensity data
• Integrate with Scope 2 reporting
• Outcome: Connect energy to climate impact

Level 3: Comprehensive Carbon

• Measure SCI (operational + embodied carbon)
• Include embodied emissions from hardware/infrastructure
• Support Scope 3 reporting
• Outcome: Full carbon lifecycle accounting

Why This Matters

Problem with "partial SCI": When organizations say "we computed the energy part of SCI," it signals failure to complete the specification.

Solution with progression: When organizations say "we computed SEE," it signals successful completion of Level 1 and celebrates progress toward Level 2 (SCE) and Level 3 (SCI).

Audience Alignment

Each level serves distinct stakeholders:

• SEE: Platform engineers optimizing infrastructure
• SCE: Sustainability teams tracking operational emissions
• SCI: Executive leadership and public disclosure

Organizations should publish all applicable levels because different audiences need different metrics for decision-making.

Clear Separation of Concerns

The matrix architecture recognizes fundamentally different skill sets for domain vs. impact work:

Domain Expertise (Software Domain Spec)

• Skills: Software architecture, system boundaries, domain-specific practices
• Contributors: Software engineers, architects, domain practitioners (AI engineers, web developers, mobile developers)
• Questions: What's the meaningful functional unit? Where does the software boundary begin/end?

Impact Expertise (Impact Specifications)

• Skills: Environmental science, LCA methodologies, measurement standards
• Contributors: Sustainability researchers, LCA practitioners, environmental scientists, academics
• Questions: How do we measure this impact? What data sources exist? What's the calculation methodology?

Examples:

• Abiotic Depletion (SAD): Requires specialized academic knowledge about resource depletion that most software engineers lack
• Water Methodology (SWE/SWI): Requires understanding of water scarcity, cooling systems, and hydrological impacts that are distinct from software domain knowledge

Benefit: Teams can work in parallel:

• Domain experts refine functional units and boundaries
• Impact experts refine measurement methodologies
• Neither blocks the other

Scalability Benefits

Adding Value Through Network Effects

As the matrix grows, each addition creates multiplicative value:

1. New domain added: Every existing impact metric immediately applies

   • Add Quantum → get SEE, SCE, SCI, SWE, SWI, SAD for Quantum automatically

2. New impact metric added: Immediately works across all domains

   • Add Biodiversity Impact → get measurements for AI, Web, Mobile, Quantum automatically

3. Domain refinement: Benefits all impact metrics simultaneously

   • Improve AI functional unit definition → improves SEE, SCE, SCI, SWE, SWI, SAD for AI

4. Impact methodology improvement: Benefits all domains simultaneously

   • Refine water calculation methodology → improves SWE for AI, Web, Mobile, Quantum

Value Compounding

The more specifications in the ecosystem:

• Greater the value of adding one more
• Lower the cost of maintaining the ecosystem (update once vs. N times)
• Faster the deployment of new capabilities (no need to create N variants)

Visual: Matrix Architecture

graph LR
    subgraph "Software Domain Spec (SD)"
        AI[AI Domain<br/>boundary + functional unit]
        Web[Web Domain<br/>boundary + functional unit]
        Mobile[Mobile Domain<br/>boundary + functional unit]
        Quantum[Quantum Domain<br/>boundary + functional unit]
    end

    subgraph "Impact Specs"
        SEE[SEE<br/>Energy methodology]
        SCE[SCE<br/>Operational Carbon]
        SCI[SCI<br/>Total Carbon]
        SWE[SWE<br/>Operational Water]
        SWI[SWI<br/>Total Water]
        SAD[SAD<br/>Abiotic Depletion]
    end

    AI -.->|applies to| SEE
    AI -.->|applies to| SCE
    AI -.->|applies to| SCI
    AI -.->|applies to| SWE
    AI -.->|applies to| SWI
    AI -.->|applies to| SAD

    Web -.->|applies to| SEE
    Web -.->|applies to| SCE
    Web -.->|applies to| SWE

    style AI fill:#e1f5ff
    style Web fill:#e1f5ff
    style Mobile fill:#e1f5ff
    style Quantum fill:#e1f5ff

    style SEE fill:#fff4e1
    style SCE fill:#fff4e1
    style SCI fill:#fff4e1
    style SWE fill:#fff4e1
    style SWI fill:#fff4e1
    style SAD fill:#fff4e1

Implementation Approach

This is a discussion document intended to elicit feedback and explore the architectural approach. Key questions for the group:

1. Does the matrix architecture address the scalability and maintenance challenges you've experienced?
2. Are there domain or impact specifications missing from this model?
3. Does the separation of domain vs. impact concerns feel natural for how work is actually done?
4. How would this affect existing specifications (SCI, emerging SEE)?
5. What governance implications does this create?

Appendix: Complete Matrix

graph TD
    SD[Software Domain Spec<br/>AI, Web, Mobile, Quantum, ...]

    SD --> E[Energy Branch]
    SD --> AD[Abiotic Depletion Branch]

    E --> SEE[SEE<br/>Operational Energy]
    SEE --> W[Water Branch]
    SEE --> C[Carbon Branch]

    W --> SWE[SWE<br/>Operational Water]
    SWE --> SWI[SWI<br/>Operational + Embodied Water]

    C --> SCE[SCE<br/>Operational Carbon]
    SCE --> SCI[SCI<br/>Operational + Embodied Carbon]

    AD --> SADE[SADE<br/>Operational Abiotic Depletion]
    SADE --> SADI[SADI<br/>Operational + Embodied Abiotic Depletion]

    style SD fill:#4a90e2,color:#fff
    style SEE fill:#50c878,color:#fff
    style SCE fill:#f39c12,color:#fff
    style SCI fill:#e74c3c,color:#fff
    style SWE fill:#3498db,color:#fff
    style SWI fill:#2980b9,color:#fff
    style SADE fill:#9b59b6,color:#fff
    style SADI fill:#8e44ad,color:#fff