Quantities, Units, Dimensions and Types (QUDT) Schema - Version 2.1.40

This version: 2.1

Latest published version: http://www.qudt.org/doc/2024/06/DOC_SCHEMA-QUDT-v2.1.html

Previous published version: https://qudt.org/doc/2024/05/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: 2024-06-26T08:27:14.139-04:00

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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, 72 classes, as indexed below:


The graph defines, or extends, 183 properties, as indexed below:


The graph defines, or extends, 28 instances, as indexed below:

 [Big Endian] 
 [Bit Encoding] 
 [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-16 String] 
 [UTF-8 Encoding] 
 [Unsigned Integer Encoding] 
 [QUDT Schema - Version 2.1.40] 

Restricted Datatypes

The graph defines, or extends, 8 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] 

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