1.
Scientific Units
in the Electronic Age
Stuart J. Chalk, Department of Chemistry
University of North Florida
schalk@unf.edu
CINF Paper 49 – 251st ACS Meeting Spring 2016
#ACSCINFDataSummit

2.
 Why Do Computers Need to Know About Units?
 What Do We Need?
 Unit Systems
 Implementation of
Units for Computers
 Text Units
 XML Units
 Semantic Units
 What We Really Need
 Things To Do
 Conclusion
Outline
From: http://unitsml.nist.gov/Presentations/UnitsML_for_TC.pdf

3.
 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!
Why do Computers
Need to Know About Units?
From: http://www.slideshare.net/petermurrayrust/text-and-data-mining-explained-at-ftdm

4.
What Do We Need?
 A way to uniquely identify and give meaning to units…
 …and dimensions, quantities, properties(?)
 A way to uniquely identify and give meaning to fundamental
constants and conversion factors
 Must describe the semantics of prefixes
 Must accommodate all languages (spoken and computer)
 Must be usable at different levels of technology
 Must be unit system agnostic
 Must be as future-proof as possible (extensible/adaptable)

5.
What Do We Need?
 A standards organization to host a platform providing
unambiguous representations of any unit of measure
 Tools/services to allow identification of units that can be
used to represent the same quantity
 Tools/services to allow systems to interconvert units and
provide a mechanism to document the conversion
 Must be compliant with the tools/services supporting big
data and the semantic web

6.
From: http://physics.nist.gov/cuu/pdf/SIDiagramColor.pdf

7.
 International System of Units (SI)
 Including CGS and MKS
 UK Imperial System
 US Customary Units
 Burmese
 Indian
 Astronomical Units
 Troy (mass) Units
 Historical/Obsolete Units and Unit Systems
https://en.wikipedia.org/wiki/List_of_obsolete_units_of_measurement
Unit Systems

8.
Implementations of
Units for Computers
 Text String
 XML (Tagged Text)
 Semantically (URI)

9.
 International Virtual Observatory Alliance (IVOA)
http://www.ivoa.net/documents/VOUnits/
 Standardization of string representations of unit
labels (“VOUnits”) in the astronomy community
Text String Representation
From: http://www.ivoa.net/documents/VOUnits/20140523/VOUnits-REC-1.0-20140523.pdf

10.
 MathML (https://www.w3.org/TR/mathml-units)
 Presentation of Units
 Unit Symbols in Content MathML
 Conversion
of Units
XML Representation
<apply>
<divide/>
<csymbol definitionURL='http://.../units/meter#c>cm</csymbol>
<csymbol definitionURL='http://.../units/second>s</csymbol>
</apply>
<apply>
<times/>
<csymbol definitionURL='http://.../units/meter#c>cm</csymbol>
<apply>
<power/>
<csymbol definitionURL='http://.../units/second>s</csymbol>
<cn type='integer'>-1</cn>
</apply>
</apply>
<csymbol definitionURL='http://.../units/kyne'>kyn</csymbol>

11.
 Geographic Markup Language (GML)
http://www.opengeospatial.org/standards/gml
 Provides
 Unit References (“unitOfMeasure” element)
 Unit Definitions (“unitDefinition” element)
 “BaseUnit”, “DerivedUnit”, and “ConventionalUnit”
XML Representation
<gml:DerivedUnit gml:id="m3">
<gml:identifier codeSpace=“…/?iid=79">cubic metre</gml:identifier>
<gml:quantityType>Volume</gml:quantityType>
<gml:derivationUnitTerm uom="#m" exponent="3"/>
</gml:DerivedUnit>

12.
 Scientific, Technical, and
Medical Publishing (STTML)
Part of the Chemical Markup Language (CML)
http://cml.sourceforge.net/schema/
XML Representation
<stm:unit id="second" name="second" unitType="time">
<stm:description>The SI unit of time</stm:description>
</stm:unit>
<stm:unit id="newton" name="newton" unitType="force”>
<stm:description>The SI unit of force</stm:description>
</stm:unit>
<stm:unit id="g" name="gram" unitType="mass" parentSI="kg" multiplierToSI="0.001"
abbreviation="g”>
<stm:description>0.001 kg.</stm:description>
</stm:unit>
<stm:unit id="inch" name="inch" parentSI="meter" abbreviation="in" multiplierToSI="0.0254" >
<stm:description>An imperial measure of length</stm:description>
</stm:unit>

13.
 UnitsML
http://unitsml.nist.gov/
 NIST Project
– intended to be published as a standard under OASIS
 Fundamental representation of dimensions, units, quantities
 UnitsDB a symbiotic project (internal to NIST)
 Never formally standardized under OASIS…
…and NIST ran out of funding
XML Representation

14.
XML
Representation
From: http://www.oasis-open.org/committees/download.php/42538/UnitsML-Guide-v1.0-wd01.pdf

15.
XML Representation
From: http://www.oasis-open.org/committees/download.php/42538/UnitsML-Guide-v1.0-wd01.pdf

16.
XML Representation
<units xmlns="http://units.nist.gov/2003/01/units/SI"
xmlns:q="http://units.nist.gov/2003/01/quantities"
xmlns:usym="http://units.nist.gov/2003/01/symbols/units”>
<unit commonName="meter" unitID="unit0001" symbol="m">
<system type="base">SI</system>
<name xml:lang="en-US">meter</name>
<name xml:lang="en-GB" >metre</name>
<name xml:lang="fr" >mètre</name>
<unitSymbolRef unitSymbolIDRef="usym:symbol0001">m</unitSymbolRef>
<quantityRef quantityIDRef="q:quantity0001" />
<history href="http://…">…</history>
<definition href="http://…">…</definition>
<remarks href="http://…">…</remarks>
</unit>
</units>

17.
XML Representation
<quantity quantityID="quantity0001” commonName="length” type="base">
<name xml:lang="en-US">length</name>
<quantSymRef quantSymbolIDRef="qsym:symbol0001">l</quantSymRef>
<dimSymRef dimSymbolIDRef="dsym:symbol0001">L</dimSymRef>
<unitSIRef unitSIIDRef="SI:unit0001" />
</quantity>
<prefix prefixID="prefix0004" commonName="mega" symbol="M” power="6" system="SI"
base="10">
<name xml:lang="en-US" >mega</name>
<prefixSymbolRef prefixSymbolIDRef="psym:symbol0004" />
</prefix>
<dimensionSymbols xmlns="http://units.nist.gov/2002/01/symbols/dimensions" >
<dimensionSymbol dimensionSymbol ID="symbol0001" commonSymbol="L">
<symbolFont family="sans-serif" style="normal" weight="bold">L</symbolFont>
</dimensionSymbol>
<dimensionSymbol dimensionSymbol ID="symbol0005" commonSymbol="Θ">
<symbolFont family="sans-serif" style="normal" weight="bold">Θ</symbolFont>
</dimensionSymbol>
</dimensionSymbols>

18.
 “Semantics” - the branch of linguistics and
logic concerned with meaning
 Rather than just identify a unit,
indicate the meaning of a unit
 Resource Description Framework (RDF)
 Subject-Predicate-Object “triples”
 RDF-XML (https://www.w3.org/TR/rdf-syntax-grammar/)
 JSON-LD (JSON for Linked Data)
 Ontological Definitions
Semantic Representation

19.
 Units of Measure Ontology (UO)
https://github.com/bio-ontology-research-group/unit-ontology
http://www.ontobee.org/ontology/UO
Semantic Representation

20.
 Semantic Web for Earth
and Environmental
Technology (SWEET)
http://sweet.jpl.nasa.gov/
 “SWEET 2.3 is highly modular
with 6000 concepts in 200
separate ontologies.”
Semantic Representation

21.
 Quantities, Units, Dimensions and Data Types Ontology (QUDT)
 Version 1
http://www.qudt.org/
 Version 2
http://www.linkedmodel.org/doc/2015/DOC_schema-qudt-v2.0
 Space Time Vocabulary
http://qudt.org/vocab/unit/units-space-and-time.html
 Physical Chemistry and Molecular Physics Vocabulary
http://qudt.org/vocab/unit/units-physical-chemistry-and-
molecular-physics.html
Semantic Representation

22.
Semantic Representation

23.
Semantic Representation

24.
Semantic Representation

25.
Semantic Units Model
From: http://www.allhands.org.uk/2006/proceedings/papers/614.pdf

26.
Semantic Units Model
From: http://www.allhands.org.uk/2006/proceedings/papers/614.pdf

27.
Semantic Units Model
From: http://www.allhands.org.uk/2006/proceedings/papers/614.pdf

28.
 A Metrology Ontology!
What Do We
Really Need?
From: http://ontology.iupac.org/ontology.pdf

29.
Official Metrology
Definitions
From: http://www.bipm.org/utils/common/documents/jcgm/JCGM_200_2012.pdf

30.
 Write up a summary of current state of units
 Develop a proposal to implement units in computers based on
best features of existing work
 Development of a metrology ontology
(33 results on google – none are a general ontology for metrology)
 Evaluate support technology needed to implement the ontology
 Identify specific use cases and implement solutions
 Formalize as a standard, with use cases and example
implementations
 Applicable for text, XML, and Semantic formats…
 ...databases, ELNs, instrument software,
Things To Do

31.
 schalk@unf.edu
 Phone: 904-620-5311
 Skype: stuartchalk
 LinkedIn/Slidehare: https://www.linkedin.com/in/stuchalk
 ORCID: http://orcid.org/0000-0002-0703-7776
 ResearcherID: http://www.researcherid.com/rid/D-8577-2013
Questions?