1. Stuart J. Chalk, Department of Chemistry University of North Florida
QUDT Toolkit: Development of a Framework to Allow Management of Digital Scientific Units
Stuart J. Chalk, Department of Chemistry University of North Florida
253rd ACS Meeting April 2017

2. Outline Why Do Computers Need to Know About Units?
Implementations of Units for Computers
QUDT
The proposal
Things To Do
Conclusion
From:

3. The Mars Climate Orbiter: A Multimillion Dollar Mistake
Although NASA declared the metric system as its official unit system in the 1980s, conversion factors remain an issue. The Mars Climate Orbiter, meant to help relay information back to Earth, is one notable example of the unit system struggle. The orbiter was part of the Mars Surveyor ’98 program, which aimed to better understand the climate of Mars. As the spacecraft journeyed into space on September 1998, it should have entered orbit at an altitude of km above Mars, but instead went as close as 57 km. This navigation error occurred because the software that controlled the rotation of the craft’s thrusters was not calibrated in SI units. The spacecraft expected newtons, while the computer, which was inadequately tested, worked in pound forces; one pound force is equal to about 4.45 newtons. Unfortunately, friction and other atmospheric forces destroyed the Mars Climate Orbiter. The project cost $327.6 million in total. Tom Gavin, an administrator for NASA's Jet Propulsion Laboratory in Pasadena, stated, "This is an end-to-end process problem. A single error like this should not have caused the loss of Climate Orbiter. Something went wrong in our system processes in checks and balances that we have that should have caught this and fixed it.”

4. Why do Computers Need to Know About Units?
Computers are used to represent data
Data is not useful unless it has a context – meaning
Part of the context of data is its unit of measure
Publication of scientific data – it needs definitive units!
Open data in repositories needs to be interoperable!
Comparing data requires unit conversions (automated)
Humans use the SI units (for example) as a standard vocabulary, computers need an equivalent

6. Units for Humans
Bureau International des Poids et Mesures (BIPM) The International System of Units (SI) International Vocabulary of Metrology (VIM)
International Organization for Standardization (ISO) ISO:80000 – Quantities and units International System of Quantities (ISQ)

7. Units for Computers – Plain Text
JCAMP Spectral Format Units – Only for units measured on the X and Y axes of spectra (
International Virtual Observatory Alliance (IVOA) “VOUnits”
Unified Code for Units of Measure

8. Units for Computers – XML
MathML (
Geographic Markup Language (GML)
Scientific, Technical, and Medical Publishing (STTML) Part of the Chemical Markup Language (CML)
Units Markup Language (UnitsML)

9. Units for Computers – Semantic
Quantities and Units of Measure Ontology Standard (QUOMOS)
Units of Measurement Ontology
Semantic Web for Earth & Environmental Technology (SWEET)
Quantities, Units, Dimensions and Data Types Ontology (QUDT)

10. QUDT - History
Development of QUDT was done as part of the NexIOM program at NASA in the late 2000s. Part of a larger semantic suite intended to represent data in the Constellation program before ultimately that program was cancelled.
QUDT lived within NASA till 2012 when…
…QUDT.org formed (not for profit)
Version 2.0 of the ontology suite is in its final development, focused on solving a number of issues related to version 1.1.

11. QUDT: Basic Structure

12. QUDT: Example Unit

13. Proposed Project
Development of a Units Repository for Administration and Dissemination of Scientific Units for Use in Semantic Applications with Ralph Hodgson, Top Quadrant and QUDT.org Steve Ray, Carnegie Mellon University and QUDT.org
Submission to the NIST Material Measurement Laboratory (MML) Grant Program

14. Proposed Project - Deliverables
Ontology suite – the framework foundation is the description of the
Concepts in metrology
SI Unit System, prefixes, and derived SI units
Quantities, QuantityKinds, Dimensions
Conversion factors, Fundamental scientific constants
Naming and Identification Rules
A reference implementation of the ontology suite for the base SI units system
Documentation – including usage examples, use cases, best practices
The Units Repository (including a units database - UnitsDB) to be hosted at NIST
Documented Application Programming Interface (API) for the Units Repository
A Validation service (also hosted at NIST) for implementers to verify they are referencing units correctly, representing units correctly, converting units correctly
Assignment of Digital Object Identifiers (DOIs) to parts of the above framework as appropriate

15. Proposed Project - Implementation

16. Other Resources A Metrology Ontology!
From:

17. Conclusion Important project for open science/open data…
…and commerce, space, energy, etc.
Still waiting on the funding
If you like this project and have suggestions of how to move funding forward at NIST (or elsewhere) contact me.

18. Questions? schalk@unf.edu Phone: 904-620-1938 Skype: stuartchalk
LinkedIn:
ORCID: