Measurement:Units

• Part of: Measurement:Main_Page

AOWIS systems, components, and data models MUST use the International System of Units (SI) as the canonical unit system.

SI is the globally accepted standard for scientific and technical measurement and is defined and maintained by the International Bureau of Weights and Measures (BIPM).

Requirements

REQ-MEAS-000: The International System of Units (SI) is the authoritative unit system for all physical quantities represented by AOWIS.

REQ-MEAS-001: All numerical values representing physical quantities within an AOWIS-compliant system MUST be represented using SI units.

REQ-MEAS-002: Implementations MUST produce results that are numerically consistent with SI-based processing.

REQ-MEAS-003: Implementations MUST NOT introduce conversion artifacts, rounding errors, or precision loss that are outside the documented precision of the measurement.

REQ-MEAS-004: Interfaces between AOWIS-compliant and non-AOWIS-compliant systems MUST convert all non-SI physical quantities to SI units before they become part of the AOWIS measurement model and MUST convert from SI units when exporting data to systems requiring non-SI units.

REQ-MEAS-005: User interfaces MUST clearly indicate the unit associated with every displayed or entered numerical value representing a physical quantity.

Non-SI unit systems MAY be used for user input and display purposes, provided that:

• All input values MUST be internally converted to SI units for storage and processing
• The original input unit MUST be preserved as metadata where applicable
• The system MUST clearly indicate the unit associated with every displayed value
• If multiple unit systems are displayed, SI units MUST be clearly identifiable as the primary reference
• Conversion between unit systems MUST be deterministic and consistent across implementations
• User interfaces MAY support alternative unit systems (e.g. imperial units), but SI units remain the authoritative representation within AOWIS.

Requirements

REQ-MEAS-UNIT-010 — All user interfaces MUST display measurement values in SI units as the primary canonical representation.

REQ-MEAS-UNIT-011 — If a user provides input in a non-SI unit (where supported), the system MUST convert the value to SI units for internal processing and display the SI value as the primary result.

REQ-MEAS-UNIT-012 — If a non-SI input unit is provided by the user, the system MUST also display the original user-provided value as secondary information, clearly labeled with its unit and explicitly marked as user-provided input (origin data).

REQ-MEAS-UNIT-013 — The SI-converted value MUST be visually and semantically distinguished as the authoritative representation of the measurement.

REQ-MEAS-UNIT-014 — The original user-provided value MUST NOT be used for calculations, control decisions, or storage without conversion to SI units.

REQ-MEAS-UNIT-015 — Unit ambiguity MUST NOT exist in any displayed measurement; each displayed value MUST have an explicitly stated unit.


* REQ-MEAS-UNIT-001 — All stored measurement values MUST use SI units as the canonical representation.
* REQ-MEAS-UNIT-002 — Non-SI input values MUST be converted to SI units before storage or processing.
* REQ-MEAS-UNIT-003 — The original input unit MUST be preserved as metadata when provided.
* REQ-MEAS-UNIT-004 — Systems MUST ensure that every displayed measurement value has an explicitly defined unit.
* REQ-MEAS-UNIT-005 — SI units MUST be identifiable as the authoritative reference in all multi-unit displays.
* REQ-MEAS-UNIT-006 — Unit conversions MUST be deterministic and consistent across implementations.
* REQ-MEAS-UNIT-007 — UI-only display formats MUST NOT affect stored or transmitted canonical SI values.