1.
OASIS Quantities and Units of Measure Ontology Standard (QUOMOS) An Introduction
v Rev. D / April 2010 1

2. Outline Goals of the QUOMOS Standard Why use an ontology?
What QUOMOS is NOT trying to do
Liaisons and existing work
This short presentation introduces QUOMOS, a new Technical Committee of OASIS, the Organization for the Advancement of Structured Information Standards. It will cover the goals of the QUOMOS project, briefly describes the advantages of using an ontology to capture the work, explains what the committee is, and is not, trying to do, and identifies other organizations and work important to systems of units. 2

3. Goals of the QUOMOS Standard
Develop a core set of ontology modules covering:
Quantities
Units
Scales
Develop extension mechanisms for non SI units and other measurement systems
Provide a consistent framework for current activities modeling units of measure
Dimensions
Base and derived SI units
Relationships between units
The goals of the QUOMOS activity are to formally encode our current system of units of measure, including definitions of quantities, units, scales, dimensions, base & derived SI units and their relationships. Using a formal approach to writing down these definitions helps in reducing errors of interpretation when they are being applied.
A second goal is in recognition of the fact that a number of projects have sprung up around the world that are tackling various portions of this problem, and it is the aim of this Technical Committee to help bring these activities into a consistent framework. It is important to note that we are not trying to force-fit all such efforts into one rigid approach, but we are attempting to ensure there are clear bridges (or maps) between different models so that the similarities and differences are clearly visible. 3

4. Why Use an Ontology?
Ontologies allow the explicit specification of the multiple possible interpretations of concepts so that people can recognize commonalities and differences in the semantics of the concepts that they use.
One might ask why an ontology is necessary for this work. An ontology, in the computer science meaning of the word, is simply “a formal representation of knowledge by a set of concepts within a domain and the relationships between those concepts. It is used to reason about the properties of that domain, and may be used to describe the domain.” [adapted from Wikipedia]. It provides a shared vocabulary, much as the VIM (Vocabulaire Internationale de Metrologie) does for the metrology community, but it does it in a formal, computer-readable language.
By using this formal approach, you gain a number of benefits… 4

5. Why Use an Ontology?
An Ontology (in this sense) is a computer readable specification, thereby enabling:
Automated consistency checking
Reasoning – i.e. deducing logical implications of assertions.
Incorporation directly into scientific and engineering software tools
You can use computer-based reasoning engines to ensure consistency and to check for errors of logic. You can also uncover possibly unanticipated implications of a new statement, or assertion.
Just as importantly, having the information in a computer-readable form makes it easy to incorporate the normative definitions of terms directly into scientific and engineering tools, thus reducing the chance of errors due to misinterpretation or misunderstanding of units being used in a system. 5

6. What QUOMOS is NOT trying to do
QUOMOS has no desire to modify any of the definitions put into place by existing authorities.
Rather QUOMOS seeks to formally encode those definitions in terms of logic statements
The OASIS QUOMOS Committee recognizes the existing authorities that are in place to define and govern the system of units and measures that support today’s scientific, engineering and business systems, and it is definitely not the intention of this committee to challenge that authority in any way.
Instead, we are seeking to strengthen our current system by formally encoding these definitions in a rigorous, formal manner, using the best information design practices available. 6

7. Liaisons
The QUOMOS committee intends to maintain good communications with:
BIPM (International Bureau of Weights and Measures)
ISO TC12
ISO/IEC 80000
VIM (International Vocabulary of Metrology)
UnitsML
UCUM (Unified Code for Units of Measure)
UNECE Recommendation 20
and others as appropriate
The TC will liaise and strive to coordinate its development with the work of BIPM (International Bureau of Weights and Measures), ISO/IEC 80000, VIM (International Vocabulary of Metrology), UnitsML, UCUM (Unified Code for Units of Measure) and UNECE Recommendation 20… 7

8. Existing Units Ontologies
QUOMOS plans to create a framework which can accommodate, and help with interoperation between existing units ontologies such as:
sciUnits of SWEET (NASA)
QUDT (TopQuadrant / NASA)
QUDV (OMG-SysML)
…and take into account existing quantities and units ontologies based on VIM, such as Sweet, QUDT and the QUDV component of SysML. It is expected that the scope of the QUOMOS ontology with respect to specific units will be influenced by the relationship to UnitsML and UCUM. 8

9. We look forward to hearing from you
Participants are welcome
Please visit:
We look forward to hearing from you
We welcome the participation by colleagues around the world as we undertake this exciting activity, and encourage you to explore the OASIS QUOMOS website shown here. We are particularly interested in maintaining strong connections with the international metrology community to ensure we are consistent with current and evolving practices. 9