Cross-device consistency needs degradation plans, not assumed parity

What it is

Cross-device consistency is achieved through degradation plans, not by assuming equal capability. Define what a pattern is meant to convey, then define a substitute rendering for each capability tier that still conveys it, rather than pushing premium parameters to every device.

Why it happens

Degradation beats parameter broadcast because users need semantics, not waveforms. One meaning can be rendered at different strengths: to distinguish two categories, a premium device can use fine rhythm while a low-tier device uses long versus short vibration. The crux is validating per device that the substitute still reaches the required identification accuracy. Skip that step and capability differences turn directly into semantic loss—invisible in the designer's validation environment.

Studying it

Study equivalence of the degraded renderings: on models at each capability tier, apply that tier's substitute and measure whether identification reaches the same threshold. Variables include the substitute dimension, capability tier, and cross-device use. Outcomes include accuracy and cross-device consistency ratings, the latter showing whether a given meaning reads the same across devices.

Where it stops holding

If the meaning depends on a premium-only dimension—the click feel of a very short pulse—degradation cannot be fully equivalent, and the choice is to relax the semantic requirement or state that the feature is unsupported on low-tier devices. Degradation also multiplies validation cost: each tier needs separate testing, so pattern table size must shrink in step.

Applying it

• Document each pattern's semantic goal rather than only its waveform parameters.
• Define substitute renderings per capability tier and validate accuracy on each tier.
• State which meanings cannot degrade and declare the supported range in the interface or documentation.
• Verification: measure accuracy on every target model and confirm the same meaning meets threshold everywhere; patterns that fail need a redesigned substitute.

Related

• Within the group: D3.14.1 Motor types and algorithms make haptics inconsistent across devices · D3.14.2 A haptic design may not reproduce at all on low-end devices
• Adjacent: D3.01.3 Motor type bounds the achievable haptic vocabulary · D2.05.3 Degradation paths must be predefined
• Search terms: graceful degradation · capability tiers · semantic equivalence