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* Part of: [[Measurement:Main_Page]]
* Part of: [[Measurement:Main_Page]]
* Related to: [[Measurement:Unit_Identifiers]]


AOWIS systems, components, and data models MUST use the International System of Units (SI) as the canonical unit system.<ref name="BIPM-SI">International Bureau of Weights and Measures (BIPM) — International System of Units (SI) https://www.bipm.org/en/measurement-units/si-base-units</ref><ref name="NIST-SI">NIST — The International System of Units (SI) https://www.nist.gov/pml/owm/metric-si/si-units</ref>
AOWIS systems, components, and data models MUST use the International System of Units (SI) as the canonical unit system.<ref name="BIPM-SI">International Bureau of Weights and Measures (BIPM) — International System of Units (SI) https://www.bipm.org/en/measurement-units/si-base-units</ref><ref name="NIST-SI">NIST — The International System of Units (SI) https://www.nist.gov/pml/owm/metric-si/si-units</ref>


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).<ref name="Wikipedia-SI">Wikipedia — International System of Units https://en.wikipedia.org/wiki/International_System_of_Units</ref>
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).<ref name="Wikipedia-SI">Wikipedia — International System of Units https://en.wikipedia.org/wiki/International_System_of_Units</ref>
== Purpose ==
This specification establishes a single authoritative unit system for all physical quantities represented by AOWIS.
The use of a single unit system reduces implementation complexity, eliminates ambiguity during data exchange, simplifies validation and testing, and improves interoperability between independent AOWIS implementations.
User Interfaces can show numerical values in non-SI units for convenience, but this is only allowed ''additionally'' to the official SI-unit, and the UI needs to transfer this to the user.


== Requirements ==
== Requirements ==
=== General ===
<pre>
<pre>
REQ-MEAS-000: The International System of Units (SI) is the authoritative unit system for all physical quantities represented by AOWIS.
REQ-MEAS-000: The International System of Units (SI) is the authoritative unit system for all physical quantities represented by AOWIS.
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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-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.
REQ-MEAS-005: Each physical quantity in AOWIS MUST be mapped to exactly one canonical SI unit.
</pre>
</pre>


 
=== User Interface Specific ===
 
 
 
 
 
 
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 ===
<pre>
<pre>
REQ-MEAS-UNIT-010 — All user interfaces MUST display measurement values in SI units as the primary canonical representation.
REQ-MEAS-UI-000: User interfaces MUST clearly indicate the unit associated with every displayed or entered numerical value representing a physical quantity.


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-UI-001: User interfaces MAY display measurement values in non-SI units for convenience, but MUST also display the corresponding SI unit value, which is the authoritative representation within AOWIS.


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-UI-002: User interfaces MUST clearly indicate that SI-based values are the authoritative representation and that non-SI values are provided for convenience only.


REQ-MEAS-UNIT-013 — The SI-converted value MUST be visually and semantically distinguished as the authoritative representation of the measurement.
REQ-MEAS-UI-003: User interfaces accepting non-SI input MUST convert all values to SI units for internal processing and MUST display the SI-converted value as the primary representation after input.


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-UI-004: Non-SI input values MAY be retained for traceability purposes but MUST NOT be used for computation, storage, or control logic within AOWIS.
 
</pre>
REQ-MEAS-UNIT-015 — Unit ambiguity MUST NOT exist in any displayed measurement; each displayed value MUST have an explicitly stated unit.


== Notes ==


* REQ-MEAS-UNIT-001 — All stored measurement values MUST use SI units as the canonical representation.
External systems MAY use alternative unit systems. Any required conversion between such systems and AOWIS is performed at the system boundary in accordance with REQ-MEAS-004.
* 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.
</pre>


== References ==
== References ==
<references />
<references />

Latest revision as of 20:36, 10 June 2026

AOWIS systems, components, and data models MUST use the International System of Units (SI) as the canonical unit system.[1][2]

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).[3]

Purpose

This specification establishes a single authoritative unit system for all physical quantities represented by AOWIS.

The use of a single unit system reduces implementation complexity, eliminates ambiguity during data exchange, simplifies validation and testing, and improves interoperability between independent AOWIS implementations.

User Interfaces can show numerical values in non-SI units for convenience, but this is only allowed additionally to the official SI-unit, and the UI needs to transfer this to the user.

Requirements

General

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: Each physical quantity in AOWIS MUST be mapped to exactly one canonical SI unit.

User Interface Specific

REQ-MEAS-UI-000: User interfaces MUST clearly indicate the unit associated with every displayed or entered numerical value representing a physical quantity.

REQ-MEAS-UI-001: User interfaces MAY display measurement values in non-SI units for convenience, but MUST also display the corresponding SI unit value, which is the authoritative representation within AOWIS.

REQ-MEAS-UI-002: User interfaces MUST clearly indicate that SI-based values are the authoritative representation and that non-SI values are provided for convenience only.

REQ-MEAS-UI-003: User interfaces accepting non-SI input MUST convert all values to SI units for internal processing and MUST display the SI-converted value as the primary representation after input.

REQ-MEAS-UI-004: Non-SI input values MAY be retained for traceability purposes but MUST NOT be used for computation, storage, or control logic within AOWIS.

Notes

External systems MAY use alternative unit systems. Any required conversion between such systems and AOWIS is performed at the system boundary in accordance with REQ-MEAS-004.

References

  1. ↑ International Bureau of Weights and Measures (BIPM) — International System of Units (SI) https://www.bipm.org/en/measurement-units/si-base-units
  2. ↑ NIST — The International System of Units (SI) https://www.nist.gov/pml/owm/metric-si/si-units
  3. ↑ Wikipedia — International System of Units https://en.wikipedia.org/wiki/International_System_of_Units
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