Established model
The double diamond
UK Design Council · 2005
Two cycles of widening then narrowing: first to find the right problem, then to find the right answer to it.
Its place in the frameworkOmni Core›UI and UX Optimization
What it does
Discover, define, develop, deliver. The reason there are two diamonds rather than one is the whole argument: teams converge on a solution before they have converged on a problem, and the first diamond exists to make that difficult. The widening halves are the ones under pressure to be skipped.
- Reach for it when
- At the start of any redesign, particularly one that began with a proposed solution.
- Where it stops
- It describes a shape, not a practice. Drawn on a plan while the team works the way it always did, it changes nothing.
UK Design Council, 2005; revised as the Framework for Innovation, 2019.
Why it sits at UI and UX Optimization
Making the things people actually use work: understanding how they are used, deciding deliberately, testing changes rather than assuming them, and being usable by everyone.
A model is only useful when you reach for it at the right moment. This one answers a question that arises here — so it is filed here, and nowhere else. These are the working areas it serves:
- Understanding useUsability-testing practice, and the finding that a small number of observed sessions surfaces the majority of significant problems.
- Design decisionsDesign-rationale practice, and interaction-design principles on consistency and recognition over recall.
- Testing changesControlled experimentation practice, and the common failure modes of underpowered and prematurely stopped tests.
- AccessibilityThe Web Content Accessibility Guidelines and the legal obligations that increasingly attach to them.
What it touches elsewhere
Nothing in a business is decided on its own. A conclusion reached with this model at UI and UX Optimization lands in these other cores, whether or not anyone follows it there.
- Customer SupportSupport contacts are the cheapest available list of interface problems, and it is rarely read as one.
- Market CoreConversion problems in the buying journey are frequently interface problems.
- Brand CoreThe visual system constrains interface design and should not prevent it from working.
- Business CoreAccessibility is a compliance obligation in most jurisdictions and belongs in the register.
Filed at the same place
These answer questions that arise at UI and UX Optimization too. Where they disagree with this one, the disagreement is the useful part.
- Nielsen’s usability heuristicsTen general principles for interface design, used as a checklist to find problems without recruiting users.
- The Fogg Behaviour ModelA behaviour happens when motivation, ability and a prompt arrive at the same moment — and fails if any is missing.
Elsewhere in Omni Core
These are other people’s models, named here so you can go to the source and use them properly. The Omnigoal is not affiliated with their authors and is not endorsed by them; nothing of theirs is reproduced here — no canvas, no diagram, no wording. Each is described in our own words, with the originator credited, because the framework is a place to put thinking, not a replacement for the people who did it. Model names and trademarks belong to their respective owners and are used here only to refer to the work itself.
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