View source for Measurement:Unit Identifiers


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

AOWIS defines a canonical set of unit identifiers used in all system interfaces, storage formats, APIs, and inter-system data exchanges.

All unit identifiers MUST be ASCII-only strings and MUST NOT contain Unicode characters, superscripts, or typographic symbols.

Units are machine-readable tokens and are not intended to represent typographic or human-rendered SI notation.

== General Rules ==

* All unit identifiers MUST be ASCII-only.
* Unit identifiers MUST be unambiguous and consistent across all AOWIS-compliant systems.
* Each physical quantity MUST map to exactly one canonical unit.
* Units MUST NOT be context-dependent or system-dependent.
* Units MUST be stable identifiers suitable for JSON, databases, and file formats.

== Requirements ==

<pre>
REQ-MEAS-UNI-001: Unit identifiers MUST be ASCII-only strings.

REQ-MEAS-UNI-002: Unit identifiers MUST NOT contain Unicode characters, superscripts, or typographic symbols.

REQ-MEAS-UNI-003: Each physical quantity in AOWIS MUST map to exactly one canonical unit identifier.

REQ-MEAS-UNI-004: Units MUST be used consistently across all AOWIS system interfaces and storage formats.

REQ-MEAS-UNI-005: Units MUST NOT be context-dependent or implementation-defined.

REQ-MEAS-UNI-006: Semantic meaning MUST be derived from the quantity field, not from the unit identifier.
</pre>

== Canonical Unit Identifiers ==

=== Length and Spatial Quantities ===

{| class="wikitable"
! Quantity !! Definition !! Canonical Unit !! EPANET Mapping
|-
| length || Linear spatial extent || m || Pipe/link length (SI-normalized EPANET model)
|-
| elevation || Vertical height relative to datum || m || Node elevation (SI-normalized EPANET model)
|-
| distance || Spatial separation between points || m || Derived geometric quantity
|-
| position_offset || Relative spatial offset magnitude || m || Not explicitly represented in EPANET
|}

=== Area and Volume ===

{| class="wikitable"
! Quantity !! Definition !! Canonical Unit !! EPANET Mapping
|-
| area || Two-dimensional spatial extent || m2 || Not directly used
|-
| volume || Storage volume || m3 || Tank volume (SI-normalized EPANET model)
|}

=== Flow and Transport ===

{| class="wikitable"
! Quantity !! Definition !! Canonical Unit !! EPANET Mapping
|-
| volumetric_flow_rate || Volume per unit time || m3_s || Link flow (SI-normalized EPANET model)
|-
| mass_flow_rate || Mass per unit time || kg_s || Not directly represented (derived)
|}

=== Pressure and Stress ===

{| class="wikitable"
! Quantity !! Definition !! Canonical Unit !! EPANET Mapping
|-
| pressure || Force per unit area in fluid system || Pa || Node pressure (SI-normalized EPANET model)
|-
| stress || Internal material stress || Pa || Not represented
|}

=== Time ===

{| class="wikitable"
! Quantity !! Definition !! Canonical Unit !! EPANET Mapping
|-
| time || Simulation or observation time || s || Simulation time (EPANET internal time normalized to seconds)
|-
| duration || Time interval length || s || Simulation duration / reporting intervals
|}

=== Electrical Quantities ===

{| class="wikitable"
! Quantity !! Definition !! Canonical Unit
|-
| current || Rate of electric charge flow || A
|-
| voltage || Electric potential difference || V
|-
| resistance || Opposition to electric current flow || ohm
|-
| power || Rate of energy transfer || W || Not represented
|-
| energy || Work or transferred electrical energy || J
|-
| capacitance || Ability to store electric charge || F
|}

== Data Representation Format ==

All AOWIS measurement values MUST use the following structure:

<pre>
{
  "quantity": "<physical_quantity>",
  "value": <numeric_value>,
  "unit": "<canonical_unit>"
}
</pre>

Example:

<pre>
{
  "quantity": "pipe_length",
  "value": 1200,
  "unit": "m"
}
</pre>