&ND v2

+++document/meta
schemaVersion = "1"
id = "aeon-gp-measurement-v1"
title = "AEON GP Measurement v1"
description = "Draft general-purpose measurement convention for units, measurement systems, precision, and currency."
family = "conventions"
group = "General-Purpose Conventions"
standing = "official"
lifecycle = "draft"
normativity = "normative"
license = "CC0-1.0"
path = "specification/conventions/aeon-gp-measurement-v1"
order = 70
publish = true
keywords = ["AEON", "measurement", "units", "precision", "currency", "measurement systems"]
related = ["aeon-conventions-overview", "measurement-reference", "compound-unit-labels"]
+++


# AEON GP Measurement v1 [# aeon-gp-measurement-v1]

Convention identifier: [$ aeon.gp.measurement.v1]

---


## 1. Purpose [# purpose]

[$ aeon.gp.measurement.v1] defines a lightweight measurement-label convention built on AEON core syntax.

It standardizes a small set of descriptive labels for:

- measurement units
- measurement systems or standards
- representational or measurement precision
- currency denominations

This convention does [* not] extend AEON core semantics.
It relies on existing AEON constructs:

- attributes ([$ @{}])
- ordinary scalar values

---


## 2. Design Goals [# design-goals]

The measurement convention aims to be:

- minimal
- predictable
- non-computational
- cross-domain
- easy to validate downstream

It provides measurement interoperability without turning AEON into a unit-conversion language.

---


## 3. Non-Goals [# non-goals]

[$ aeon.gp.measurement.v1] does [* not require AEON core] to:

- convert units
- normalize numeric values
- infer measurement systems
- compute derived values
- perform exchange-rate logic

Examples:

~~~$ aeon
distance@{unit="m"} = 3
price@{currency="AUD"} = 19.95
~~~$

These statements only label the data.

Any computation or interpretation belongs to:

- schemas
- profiles
- processors
- application logic

---


## 4. Core Principle [# core-principle]

A measurement convention defines interpretation agreements, not language semantics.

AEON core preserves:

- bindings
- attributes
- scalar values

The convention defines how these preserved patterns are commonly understood by cooperating consumers.

---


## 5. Reserved Measurement Keys [# reserved-measurement-keys]

The following lowercase attribute keys have defined meaning under [$ aeon.gp.measurement.v1].

Attribute keys defined by this convention [* must be lowercase ASCII identifiers].

Unknown keys remain allowed and are treated as opaque unless defined elsewhere.

| Key           | Purpose                                    |
| <--           | <--                                        |
| [$ unit]      | measurement unit label                     |
| [$ system]    | measurement system or standard context     |
| [$ precision] | representational or measurement resolution |
| [$ currency]  | monetary denomination                      |
|~ Reserved measurement keys

---


### 5.1 [$ unit] [# unit]

Declares a measurement unit label associated with a value.

~~~$ aeon
distance@{unit="m"} = 3
weight@{unit="kg"} = 82
temperature@{unit="C"} = 21
~~~$

Meaning:

- identifies the unit of measurement
- purely descriptive
- does not imply conversion or calculation

---


### 5.2 [$ system] [# system]

Declares the system or standard context in which a unit or label should be interpreted.

~~~$ aeon
mass@{unit="oz", system="avoirdupois"} = 12
volume@{unit="oz", system="US-fluid"} = 8
distance@{unit="mile", system="imperial"} = 3
length@{unit="m", system="metric"} = 10
~~~$

Meaning:

- disambiguates unit systems
- provides contextual classification
- does not imply conversion behavior

---


### 5.3 [$ precision] [# precision]

Declares the intended representational or measurement resolution of a value.

~~~$ aeon
length@{unit="mm", precision=0.1} = 125.4
temperature@{unit="C", precision=0.01} = 21.37
price@{currency="AUD", precision=0.01} = 19.95
~~~$

Meaning:

- indicates expected granularity or accuracy
- does not require rounding or formatting

---


### 5.4 [$ currency] [# currency]

Declares a currency denomination associated with a numeric value.

~~~$ aeon
price@{currency="AUD"} = 19.95
budget@{currency="EUR"} = 500
~~~$

Meaning:

- identifies monetary denomination
- does not imply exchange-rate logic or accounting rules

---


## 6. Unknown Keys [# unknown-keys]

The measurement convention permits extension.

Rule:

- known reserved keys have stable meaning
- unknown keys may appear
- unknown keys should be treated as opaque unless a schema, profile, or another convention defines them

This enables forward compatibility.

---


## 7. Validation Posture [# validation-posture]

[$ aeon.gp.measurement.v1] itself is descriptive.

Validation belongs to downstream layers.

Examples:

A schema might require:

- [$ currency] to match ISO codes
- [$ unit] to match an allowed list
- [$ precision] to match allowed increments

These checks are [* not AEON core responsibilities].

---


## 8. Example Document [# example-document]

~~~$ aeon
aeon:header = {
  convention = "aeon.gp.measurement.v1"
}

distance@{unit="m", system="metric", precision=0.01} = 3
price@{currency="AUD", precision=0.01} = 19.95

mass@{unit="oz", system="avoirdupois"} = 12
~~~$

---


## 9. Interpretation Summary [# interpretation-summary]

| Pattern                | Meaning                     |
| <--                    | <--                         |
| [$ @{unit="m"}]        | measurement unit label      |
| [$ @{system="metric"}] | measurement system context  |
| [$ @{precision=0.01}]  | representational resolution |
| [$ @{currency="AUD"}]  | monetary denomination       |
|~ Measurement interpretation patterns

---


## 10. Definition [# definition]

[$ aeon.gp.measurement.v1] is a versioned interoperability convention that standardizes common measurement labels using
AEON core constructs, without extending AEON core semantics.