Quantities, Units, Dimensions and Types (QUDT) Schema - Version 2.1.17

This version: 2.1

Latest published version: http://www.qudt.org/doc/2022/04/DOC_SCHEMA-QUDT-v2.1.html

Previous published version: http://www.qudt.org/doc/2022/02/DOC_SCHEMA-QUDT-v2.1.html

Editor: Ralph Hodgson, TopQuadrant, Inc

Contributors: Daniel Mekonnen, David Price, Jack Hodges, James E. Masters, Simon J D Cox, Steve Ray

Last Modified: 2022-04-20T11:00:01.493-04:00

Copyright © 2011 - 2022 qudt.org , All Rights Reserved.

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The QUDT, or "Quantity, Unit, Dimension and Type" schema defines the base classes properties, and restrictions used for modeling physical quantities, units of measure, and their dimensions in various measurement systems. The goal of the QUDT ontology is to provide a unified model of, measurable quantities, units for measuring different kinds of quantities, the numerical values of quantities in different units of measure and the data structures and data types used to store and manipulate these objects in software.

Except for unit prefixes, all units are specified in separate vocabularies. Descriptions are provided in both HTML and LaTeX formats. A quantity is a measure of an observable phenomenon, that, when associated with something, becomes a property of that thing; a particular object, event, or physical system.

A quantity has meaning in the context of a measurement (i.e. the thing measured, the measured value, the accuracy of measurement, etc.) whereas the underlying quantity kind is independent of any particular measurement. Thus, length is a quantity kind while the height of a rocket is a specific quantity of length; its magnitude that may be expressed in meters, feet, inches, etc. Or, as stated at Wikipedia, in the language of measurement, quantities are quantifiable aspects of the world, such as time, distance, velocity, mass, momentum, energy, and weight, and units are used to describe their measure. Many of these quantities are related to each other by various physical laws, and as a result the units of some of the quantities can be expressed as products (or ratios) of powers of other units (e.g., momentum is mass times velocity and velocity is measured in distance divided by time).

The namespace prefix for resources in this ontology is: qudt

The schema graph is available as: Turtle

Table of Contents

  1. Resource Index
    1. Imported Graphs
    2. Non-imported Resources
  2. Resource Details
    1. Classes
    2. Properties
    3. Instances

Imported Graphs

A list of graphs imported by http://qudt.org/2.1/schema/qudt is shown below.

Graph URIIntent
http://www.linkedmodel.org/schema/dtypeThe purpose of DTYPE is to provide, by import, a foundation for data types.
http://www.linkedmodel.org/schema/vaemThe purpose of VAEM is to provide, by import, a foundation for commonly needed resources for metadata on an ontology.

Non-imported Resources

The graph uses 12 resources from other graphs that are not imported, as listed below:

Resource Index

The main namespace for resources in this graph is http://qudt.org/schema/qudt/ with the prefix qudt.


The graph defines, or extends, 68 classes, as indexed below:

Quantity Kind (abstract)
Aspect Class
Base Dimension Magnitude
Binary Prefix
Bit Encoding
Boolean encoding type
Byte Encoding
Cardinality Type
Char Encoding Type
QUDT Concept
Constant value
Counting Unit
Currency Unit
Data Encoding
QUDT Datatype
Date Time String Encoding Type
Decimal Prefix
Derived Unit
Dimensionless Unit
Endian Type
Enumerated Value
Enumeration scale
Floating Point Encoding
Integer Encoding
Interval scale
Logarithmic Unit
Math Function Type
NIST SP~811 Comment
Nominal scale
Ordered type
Ordinal scale
Physical Constant
Quantity Kind
Quantity Kind Dimension Vector
CGS EMU Dimension vector
CGS ESU Dimension vector
CGS GAUSS Dimension vector
CGS LH Dimension vector
Imperial dimension vector
Quantity Kind Dimension vector (SI)
Quantity type
Quantity value
Ratio scale
Rule Type
Scalar Datatype
Scale type
Signedness type
String Encoding Type
Structured Data Type
System of Quantity Kinds
System of Units
User Quantity Kind


The graph defines, or extends, 184 properties, as indexed below:


The graph defines, or extends, 27 instances, as indexed below:

Big Endian
Boolean Encoding
Countably Infinite Cardinality Type
Finite Cardinality Type
Uncountable Cardinality Type
Char Encoding
Single Precision Real Encoding
IEEE 754 1985 Real Encoding
ISO 8601 UTC Date Time - Basic Format
Little Endian
Long Unsigned Integer Encoding
OCTET Encoding
Partially Ordered
Short Signed Integer Encoding
Short Unsigned Integer Encoding
Signed Integer Encoding
Single Precision Real Encoding
Totally Ordered
UTF-8 Encoding
Unsigned Integer Encoding
QUDT Schema - Version 2.1.17

Restricted Datatypes

The graph defines, or extends, 10 restricted datatypes, as indexed below:

Latex String
case-insensitive UCUM code
case-insensitive UCUM term
case-sensitive UCUM code
case-sensitive UCUM terminal
float percentage
integer percentage
value union
`float [xsd:float]`[>= "0.00"^^`float [xsd:float]` , <= "100.00"^^`float [xsd:float]`]
`integer`[>= 0 , <= 100]

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