Maps the solution space of a design, architecture, or business-model problem with General Morphological Analysis (Zwicky box, 1969; Ritchey's Cross-Consistency Assessment) — parameters × discrete values, every cross-parameter value pair judged consistent or excluded for a stated reason, then the count and shortlist of internally consistent configurations. Use when many interacting choices must be explored without missing viable combinations — "map all viable configurations", "Zwicky box / morphological analysis", "how many internally consistent combinations exist?", "prune the impossible combos". Not for consequences of one decision (`futures-wheel`) or 2×2 futures (`scenario-planning`).
Maps the solution space of a design, architecture, or business-model problem with General Morphological Analysis (Zwicky box, 1969; Ritchey's Cross-Consistency Assessment) — parameters × discrete values, every cross-parameter value pair judged consistent or excluded for a stated reason, then the count and shortlist of internally consistent configurations. Use when many interacting choices must be explored without missing viable combinations — "map all viable configurations", "Zwicky box / morphological analysis", "how many internally consistent combinations exist?", "prune the impossible combos". Not for consequences of one decision (`futures-wheel`) or 2×2 futures (`scenario-planning`).
license
MIT
metadata
{"category":"decision-strategy","method":"General Morphological Analysis (GMA) with Cross-Consistency Assessment (CCA)","origin":"Fritz Zwicky, Caltech, 1940s (book 1969); computer-aided GMA and CCA — Tom Ritchey, Swedish Defence Research Agency / Swedish Morphological Society, 1995–2006","version":"2.0.0"}
General Morphological Analysis (Zwicky box + CCA)
General Morphological Analysis (GMA) is Fritz Zwicky's method (Caltech, 1940s; Discovery, Invention, Research through the Morphological Approach, 1969) for structuring a multi-dimensional, non-quantifiable problem: name its parameters, list each one's discrete values, and treat every combination of one value per parameter as a candidate configuration. Tom Ritchey's computer-aided form (Swedish Defence Research Agency, 1995–2006) adds Cross-Consistency Assessment (CCA): every value pair is judged for mutual consistency and only the survivors form the solution space. It prevents anchoring on the few familiar combinations while viable ones go unexamined.
When to invoke
Invoke when:
A product architecture, business model or policy option has 4–8 interacting choices and all viable combinations matter — "map the solution space", "explore all viable architectures", "Zwicky box", "morphological analysis".
The question is how many internally consistent configurations exist and which contain a required feature ("must sell grid flexibility").
Do NOT invoke when:
The change is fixed and the question is its downstream effects — futures-wheel.
Two critical uncertainties are to be narrated into four futures — scenario-planning; GMA is for more than two dimensions where consistency is the issue.
Trends influence each other directionally — cross-impact-analysis; CCA judges compatibility, never causation.
The problem cannot yet be stated as parameters — decompose-research-question first.
A shortlist already exists and needs scoring or testing — decision-matrix-mcda, then cheapest-experiment.
Procedure — the Zwicky/Ritchey cycle
1 — Define the problem and its parameters
State the problem in one sentence. Choose 4–8 parameters (dimensions) — the independent questions any solution must answer ("what stores energy?", "who owns the hardware?"). Parameters must be MECE: no parameter is a value of another, and one value per parameter fully specifies a configuration. Beyond eight the field becomes unwieldy.
2 — List the values of each parameter
Give each parameter 2–6 discrete, named values (Ritchey: "conditions"). Discretise continuous quantities into bands (5 kWh / 15 kWh); include "none" when it is a real option. Values within a parameter are mutually exclusive by construction — that is what makes the field a box, not a checklist.
3 — Build the box and size the raw space
Set the parameters as columns with their values beneath — the morphological field, or Zwicky box. The raw count is the product of the value counts, N = n₁ × n₂ × … × nₖ (morph.py box): five parameters with 3–4 values give 432 configurations; 6–10 parameters give 50,000–5,000,000 (Ritchey 2006).
4 — Cross-Consistency Assessment
Compare every value with every value of every other parameter, pair by pair, asking only "can these two coexist?" — no direction, no causality. Record each pair as consistent, or excluded as a logical contradiction (the concepts cannot both hold), an empirical implausibility (very unlikely on evidence) or a normative exclusion (ruled out by policy, law or values — Ritchey: use sparingly, label clearly), each with a one-line reason. Pairs grow only quadratically (115 against 432 configurations below), which is why the field is reducible; morph.py cca lists what is still un-assessed.
5 — Derive the solution space
Configurations containing no excluded pair are the internally consistent solution space. Count them and the reduction with morph.py space; Ritchey reports typical fields shrinking by 90–99 %. A tiny reduction means a permissive CCA; a total one means a wrong exclusion or an over-constrained problem — revisit step 4.
6 — Select drivers and label configurations
Fix one or more values as drivers — a required feature or a scenario condition — and list the consistent configurations containing them (morph.py solutions --must). Name each interesting configuration and note what would have to be true for it to work.
7 — Report
Fill the output template: problem, box, raw versus consistent counts, exclusion register, drivers, named shortlist. The exclusions are the analysis; the counts merely follow, so show the reasons.
Every field is mandatory — without the exclusion register the count has no argument.
Worked example
Problem: which architectures for a residential home-energy product are internally consistent, and which can sell grid flexibility? Five parameters — Storage (3 values), Control (4), Revenue (3), Ownership (3), Pricing (4) — and nine reasoned exclusions (examples/home-energy.json). python3 scripts/morph.py --demo prints (header lines omitted):
Parameters: Storage(3) × Control(4) × Revenue(3) × Ownership(3) × Pricing(4)
Raw configurations: 3 × 4 × 3 × 3 × 4 = 432
Exclusions: 9 value pairs (logical 5, empirical 3, normative 1) in 5 of 10 parameter-pair blocks (115 value pairs to assess in total)
Consistent configurations: 172 of 432 (260 removed = 60.2 % reduction)
Consistent configurations containing Revenue:Grid flexibility (VPP): 54 of 172 consistent (raw 432)
# Storage Control Revenue Ownership Pricing
1 Small battery (5 kWh) Rule-based schedule Grid flexibility (VPP) Customer-owned One-off purchase
2 Small battery (5 kWh) Rule-based schedule Grid flexibility (VPP) Customer-owned Monthly subscription
(showing 2 of 54; raise --limit to see more)
Nine judgements out of 115 removed 260 of 432 configurations. Two do most of the work: Storage: None × Revenue: Tariff arbitrage (logical — nothing to shift) and Control: Manual app × Revenue: Grid flexibility (VPP) (logical — dispatch is machine-to-machine); with the empirical exclusion of controls-only VPP they force every VPP configuration onto a battery with automated control, so 2 × 3 × 9 = 54 survive the driver. The single normative exclusion (Customer-owned × Bundled in tariff, company policy) removes 36 configurations a policy decision could restore. Shortlist: "Buy-and-earn" (small battery, cloud optimiser, VPP, customer-owned, revenue share — works if the aggregator contract clears the customer's payback threshold); "Utility VPP fleet" (large battery, local edge optimiser, VPP, utility-owned, bundled in tariff — rests on the utility carrying the asset). morph.py cca reports CCA COMPLETE for all 10 blocks, so the count is a finding, not an artefact of un-assessed pairs.
Verification
Before shipping, confirm:
Parameters are MECE — no parameter is a value of another; nothing continuous left un-banded.
Every cross-parameter value pair assessed — morph.py cca exits 0 with CCA COMPLETE; silence is never read as consistent.
Every exclusion has a type and a reason a colleague could dispute; normative exclusions are few and labelled.
Raw count = product of the value counts; consistent count reconciled with morph.py space after every edit.
Each shortlisted configuration appears in morph.py solutions --must output — it contains the drivers and violates no exclusion.
Companion tool
scripts/morph.py does the arithmetic of steps 3–6 from a JSON box (parameters; exclusions with type and reason; optional consistent pairs and assessed_blocks): raw and consistent counts, deterministic solution listing with driver filters, CCA coverage. Stdlib only, offline; every command takes --json.
scenario-planning — Ritchey pairs an external scenario field with an internal strategy field; hand consistent configurations to the 2×2 method or vice versa.
futures-wheel — map the consequences of the configuration finally chosen.
cross-impact-analysis — when interactions are directional influences, not compatibilities.
decompose-research-question — turns a sprawling question into step 1's parameters.
key-assumptions-check — audit the premises behind the empirical and normative exclusions.
decision-matrix-mcda — score the shortlisted configurations against weighted criteria.
cheapest-experiment — the smallest test for each shortlisted configuration.
T. Ritchey, "Problem structuring using computer-aided morphological analysis," Journal of the Operational Research Society 57(7):792–801, 2006. https://doi.org/10.1057/palgrave.jors.2602177
A. Álvarez and T. Ritchey, "Applications of General Morphological Analysis: From Engineering Design to Policy Analysis," Acta Morphologica Generalis 4(1), 2015, ISSN 2001-2241. https://www.swemorph.com/amg/pdf/amg-4-1-2015.pdf
R. H. Pherson and R. J. Heuer Jr., Structured Analytic Techniques for Intelligence Analysis, 3rd ed. CQ Press / SAGE, 2019, ch. 9, §9.8 "Morphological Analysis". ISBN 978-1-5063-6893-1.
