HIF / Documentation / Normative contract

Interface Constitution

Version: 0.1

This document defines the universal normative requirements of the Human Interface Framework. A Product Profile MAY strengthen these requirements, but MUST NOT weaken them without a recorded exception and risk assessment.

The key words MUST, MUST NOT, SHOULD, SHOULD NOT and MAY are to be interpreted as normative levels.

1. Context and purpose

HIF-CTX-001. Explicit purpose

The interface MUST be designed around identified people, tasks and contexts, not merely around available technology or a component inventory.

HIF-CTX-002. Product boundaries

The interface MUST distinguish honestly between an available capability, a prototype, a demonstration, a planned capability and an external dependency.

HIF-CTX-003. Risk level

The risk of error MUST be assessed for consequential actions. Prevention, confirmation and recovery MUST be proportionate to that risk.

2. Objects and identity

HIF-OBJ-001. Stable identity

An object MUST retain its identity across changes of representation, theme, device and context unless the product model explicitly creates a new object.

HIF-OBJ-002. Object is not representation

Closing, hiding or deleting a representation MUST NOT implicitly delete the underlying object, data or access where these are distinct entities.

HIF-OBJ-003. Distinguishable types

Entity types with materially different consequences MUST be distinguishable in terminology, state and available commands.

HIF-OBJ-004. Provenance

Where provenance affects trust, rights or safety, it MUST be available before a person commits a consequential action.

3. Commands and consequences

HIF-CMD-001. Semantic command

Every consequential action MUST be represented by a semantic command with defined preconditions, effects, authority, reversibility and outcomes.

HIF-CMD-002. Independence from gesture

A command's meaning MUST be independent of any particular pointer, touch, keyboard, voice or automation binding.

HIF-CMD-003. Truthful name

A command's name and description MUST correspond to its actual effect.

HIF-CMD-004. Command availability

An unavailable command MUST either explain why it is unavailable or be omitted when no useful explanation can be given. It MUST NOT appear available and then silently ignore input.

HIF-CMD-005. Idempotence

A command SHOULD be idempotent where repetition has no independent meaning. The system MUST guard against accidental repetition of consequential actions.

4. State

HIF-STA-001. State visibility

State required for a decision MUST be available at the point of decision.

HIF-STA-002. Distinguishability

Active, selected, focused, checked, expanded, enabled, pending, completed and error states MUST be modelled separately wherever the product distinguishes them.

HIF-STA-003. Source of truth

Each state MUST have one normative source of truth. Multiple representations MAY display it but MUST NOT diverge semantically.

HIF-STA-004. Persistence

For mutable state, the duration and scope of persistence MUST be defined and material persistence MUST be understandable to the user.

HIF-STA-005. Concurrent change

Where another actor, device or process can change state, the interface MUST detect relevant conflict and MUST NOT present stale state as current.

5. Feedback

HIF-FBK-001. Action acceptance

The system MUST clearly acknowledge acceptance of an action or promptly explain its refusal.

HIF-FBK-002. Progress

An operation that does not complete immediately MUST expose meaningful progress or status. Where measurable, the indicator SHOULD report actual progress.

HIF-FBK-003. Completion

The outcome MUST be available in a location and form connected to the original task.

HIF-FBK-004. Background change

A consequential change outside the current focus MUST remain discoverable without creating unjustified interruption.

HIF-FBK-005. Truth before optimism

Optimistic presentation MAY be used only when expected and confirmed outcomes remain distinguishable and failure can be recovered correctly.

6. Errors and recovery

HIF-ERR-001. Prevention

The system SHOULD prevent foreseeable, costly errors before they occur without blocking safe exploration.

HIF-ERR-002. System responsibility

An error message MUST explain the problem without blaming the user and SHOULD distinguish invalid input, a system limitation, dependency failure and insufficient authority.

HIF-ERR-003. Recovery

An error state MUST provide a feasible next action: correct, retry, undo, restore, seek help or exit safely.

HIF-ERR-004. Preservation of work

Failure MUST NOT discard valid user work where preservation is technically and ethically possible.

HIF-ERR-005. Undo

Frequent or consequential reversible actions SHOULD provide undo. Where literal undo is impossible, the system SHOULD provide an explicit compensating action.

HIF-NAV-001. Orientation

A person MUST be able to determine their current location, relevant context and available routes.

HIF-NAV-002. Predictability

Equivalent navigation actions SHOULD have equivalent effects throughout the same product profile.

HIF-NAV-003. Focus

Keyboard and assistive-technology focus MUST be visible, programmatically exposed and ordered according to the task rather than visual accident.

HIF-NAV-004. Focus restoration

After a temporary layer closes or content changes, focus MUST return to a logical, predictable location.

HIF-NAV-005. Escape

A temporary mode, layer or capture state MUST provide a reliable and discoverable means of leaving it.

8. Input methods

HIF-INP-001. Primary-function independence

A primary function MUST NOT depend solely on precise pointing, dragging, hovering, timing or another single input ability.

HIF-INP-002. Equivalence

Supported input methods MUST provide semantically equivalent access to primary commands, except where the method itself is intrinsic to the task.

HIF-INP-003. Conflicts

Input bindings MUST NOT silently override established platform, accessibility or safety conventions.

HIF-INP-004. Shortcut visibility

Shortcuts that materially improve frequent work SHOULD be discoverable in the interface or its immediately available help.

9. Accessibility and adaptation

Accessibility MUST be part of the semantic and interaction architecture, not a post-production visual adjustment.

The interface MUST respect applicable preferences for contrast, text size, motion, colour scheme, input and assistive technology.

Content and primary functions MUST remain usable under supported zoom, text enlargement, viewport change and reflow conditions.

Implementation cost, visual purity or convention alone MUST NOT be used to exclude a group from a primary function.

10. Content and language

HIF-CNT-001. User language

Content MUST use terminology that the intended audience can understand. Specialist terms MUST be necessary, defined or supported by context.

HIF-CNT-002. Specificity

Labels, instructions and errors MUST identify the relevant object, action and consequence with enough specificity to support a decision.

HIF-CNT-003. Localisation

Localisation MUST preserve meaning, normative force, content hierarchy and interaction viability rather than merely substituting strings.

HIF-CNT-004. Human and machine form

Where information is both machine-readable and human-facing, neither form MUST silently contradict the other.

11. Privacy, security and trust

HIF-TRU-001. Informed action

Before a consequential transfer, disclosure, purchase, permission or destructive act, the interface MUST disclose the material consequence.

HIF-TRU-002. Symmetry of choice

Accepting and refusing a non-essential option MUST be comparably understandable and accessible.

HIF-TRU-003. Least privilege

The interface MUST request only the authority needed for the stated task and MUST explain materially unusual permissions.

HIF-TRU-004. Destructive actions

Destructive actions MUST be visually and semantically distinguishable, proportionately confirmed and followed by recovery where feasible.

HIF-TRU-005. No dark patterns

The interface MUST NOT manipulate choice through concealment, obstruction, false urgency, confirmshaming, disguised advertising or asymmetric friction.

12. Automation and AI

HIF-AUT-001. Proposal is not execution

A suggestion, preview or generated plan MUST remain distinct from an executed action.

HIF-AUT-002. Boundary of authority

Automation MUST act only within authority granted for the task. Expansion of scope requires new, informed authorisation.

HIF-AUT-003. Verifiable intent

Before a consequential automated action, the person MUST be able to verify the target, scope and expected effect.

HIF-AUT-004. Observability

Material automated actions MUST leave an understandable record of what acted, when, on what object and with what result.

HIF-AUT-005. Correctability

Automation SHOULD be interruptible, reversible or compensatable in proportion to its risk and duration.

HIF-AUT-006. Uncertainty

An AI-mediated interface MUST represent material uncertainty and MUST NOT present inference as verified fact.

13. Performance and resilience

HIF-PERF-001. Readiness

The interface MUST distinguish loading, interactive readiness and completed work where the difference affects action.

HIF-PERF-002. Stability

Late content and asynchronous updates MUST NOT cause avoidable loss of context, focus, target position or entered data.

HIF-PERF-003. Progressive enhancement

A core task SHOULD remain available under reduced capability, bandwidth or presentation whenever the product context permits it.

HIF-PERF-004. Preservation of result

An acknowledged successful result MUST survive navigation, refresh or transient connection loss according to the product's stated persistence model.

14. Visual system

HIF-VIS-001. Hierarchy

Visual hierarchy MUST correspond to semantic importance, structure and task order.

HIF-VIS-002. State beyond colour

Colour MUST NOT be the sole carrier of consequential state or instruction.

HIF-VIS-003. Consistent meaning

Equivalent visual forms SHOULD carry equivalent meanings within a product profile; materially different meanings SHOULD remain distinguishable.

HIF-VIS-004. Theme preserves semantics

A theme MAY change visual expression but MUST preserve information, interaction, state and accessibility semantics.

HIF-VIS-005. Third-party material

Third-party fonts, icons, images, sound and other assets MUST have verified licensing, attribution and redistribution conditions before release.

15. Colour system

HIF-COL-001. Semantics before swatches

The information, action, hierarchy and state represented by a colour role MUST be defined before a colour value is selected. A brand seed or preferred swatch MUST NOT determine interface semantics.

HIF-COL-002. Declared colour contract

Every colour system MUST declare its working and delivery colour spaces, baseline gamut, optional enhanced gamuts, conversion and gamut-mapping policy, precision and algorithm versions.

HIF-COL-003. Controlled emphasis

Every product profile MUST define an area, chroma and emphasis policy. High-chroma colour MUST be reserved for identified roles and MUST NOT cause unrelated regions or actions to compete for attention.

HIF-COL-004. Deterministic derivation

A generated palette MUST be reproducible from recorded seeds, constraints, lightness targets, chroma policy, gamut policy and algorithm version. Manual exceptions MUST be explicit, justified and reviewable.

HIF-COL-005. Semantic token boundary

Product and component code MUST consume semantic or component colour tokens, not primitive palette names or ungoverned colour literals. A theme MAY remap a semantic token but MUST NOT change its meaning.

HIF-COL-006. Rendered contrast

Required foreground, background, boundary, focus and state combinations MUST meet the applicable contrast contract in every supported mode and state. Palette-level calculations MUST NOT substitute for testing the rendered combination.

HIF-COL-007. Meaning beyond colour

Consequential information, status, validation and instruction MUST have a non-colour cue sufficient to identify their meaning when colour is unavailable or cannot be distinguished.

HIF-COL-008. Independent modes and preferences

Light and dark schemes, contrast preferences, forced colours, brand variants and environmental adaptations MUST be modelled as independent dimensions. User and platform accessibility settings take precedence over brand fidelity.

HIF-COL-009. Complete state matrix

Every interactive role MUST specify and verify rest, hover, active, focus-visible, selected, disabled, read-only, invalid, busy and relevant combined states. Fixed opacity alone MUST NOT derive states that require distinguishable meaning or contrast.

HIF-COL-010. Gamut-safe fallback

Every required colour token MUST have a conforming baseline-gamut value. Wide-gamut enhancement MAY increase expression but MUST preserve hierarchy, contrast, state distinction and meaning in its fallback.

HIF-COL-011. Evidence before release

A colour-system release MUST record inputs, generated values, semantic mappings, required pairs, automated results, rendered and human review, exceptions, residual risks, owner and version. Approval by taste or a palette sheet alone is insufficient.