1. @wernerkeil | @UnitAPI#JSR363 | #EclipseScience | #ECE2016
The First IoT JSR: Units of Measurement
JSR-363
Werner Keil
@wernerkeil & @UnitAPI
https://www.jcp.org/en/jsr/detail?id=363
http://unitsofmeasurement.github.io

2. @wernerkeil | @UnitAPI#JSR363 | #EclipseScience | #ECE2016
The First IoT JSR: Units of Measurement
Werner Keil
•Consultant – Coach
•Creative Cosmopolitan
•Open Source Evangelist
•Software Architect
•Spec Lead – JSR363, Eclipse UOMo Project Lead
•Individual JCP Executive Committee Member
[www.linkedin.com/in/catmedia]

3. @wernerkeil | @UnitAPI#JSR363 | #EclipseScience | #ECE2016
What are Units of Measurement?
6,089 ??????
A Measurement
A Unit

4. @wernerkeil | @UnitAPI#JSR363 | #EclipseScience | #ECE2016
What is the problem, in code?
int distance = 6089; //in ???
float speed = airplane.getSpeed(); //in ???
System.out.println(“TTD: “ + (distance/speed) + “
hours”);
6,089 ??????
A Measurement
A Unit

5. @YourTwitterHandle#DVXFR14{session hashtag} @wernerkeil | @UnitAPI#JSR363 | #EclipseScience | #ECE2016
LEARNING FROM THE PAST…
Some examples of how things can go wrong…

6. @wernerkeil | @UnitAPI#JSR363 | #EclipseScience | #ECE2016
Some real-life mishaps…
NASA “Star Wars” Initiative, 1985
Sea Level

7. @wernerkeil | @UnitAPI#JSR363 | #EclipseScience | #ECE2016
NASA Mars Climate Orbiter, 1999
Some real-life mishaps…
[Cost $125M-300M]
“Preliminary findings indicate that one team used US/English units
(e.g. inches, feet and pounds) while the other used metric units for a key
spacecraft operation.”

8. @wernerkeil | @UnitAPI#JSR363 | #EclipseScience | #ECE2016
2001: Escape of the 250Kg tortoise
Los Angeles Zoo lent Clarence, a 250-kilogram, 75-
year-old Galapagos tortoise, to the Exotic Animal
Training and Management Program at Moorpark
College in Moorpark CA.
The first night in his new home, Clarence wrecked it:
“He just pushed one of the fence poles right
over,” said Moorpark's Chuck Brinkman.
The L.A. Zoo warned that Clarence was big, and
needed an enclosure for an animal that “weighs
in at about 250”, so that's what the college
built.
Unfortunately, they thought the zoo meant 250
pounds, so the enclosure wasn't adequate for
holding a 250-kilogram (552 lbs) beast.
Clarence

9. @wernerkeil | @UnitAPI#JSR363 | #EclipseScience | #ECE2016
Why do we need a specification?
There are no specifications or standards for handling units in Java.
The current solution is to use primitives, that don’t provide any Type
Safety.
The errors are difficult to find using unit testing:
Interface and Internationalization (e.g. radian/degree, meters/feet);
Arithmetic operations (e.g. overflow);
Conversion between units (e.g. from same domain);

10. @wernerkeil | @UnitAPI#JSR363 | #EclipseScience | #ECE2016
What is JSR-363?
Interfaces and abstract classes supporting unit operations including:
Checking of unit compatibility;
Expression of measurement in various units; and
Arithmetic operations on units.
Concrete classes implementing standard unit types (base, derived) and
unit conversion.

11. @wernerkeil | @UnitAPI#JSR363 | #EclipseScience | #ECE2016
What is a Unit?
c. (a) Any determinate quantity, dimension, or magnitude adopted as a
basis or standard of measurement for other quantities of the same kind
and in terms of which their magnitude is calculated or expressed.
Oxford English Dictionary
Or … A well defined standard we all know?
Unit Definition
Second The duration of 9,192,631,770 periods of the radiation corresponding to the
transition between the two hyperfine levels of the ground state of caesium 133 atom
Kilogram The mass of the international prototype kilogram [a very special lump of metal]
metre The distance travelled by light in a vacuum in
3.3356409519815204957557671447492e-9 seconds

12. @wernerkeil | @UnitAPI#JSR363 | #EclipseScience | #ECE2016
A Standard Measurement …
“The nice thing about standards is that you have so many to choose
from.”
Andrew S. Tanenbaum,
Computer Networks 2nd ed., p. 254
Foot
Mile
Yard Chain
Fathom
Furlong
InchNautical Mile
Statute Mile
astronomical unit (AU)
Light year
Parsec(or meter)
Passus (roman)
Hand
ångström
Scots/Welsh/English Mile
Metre fermi micron
Thou (or mil)League
rod/perch/pole
nail
Barleycorn
link
ell Cubitfinger
palm
Poppyseed
Milli Centi Kilo

13. @wernerkeil | @UnitAPI#JSR363 | #EclipseScience | #ECE2016
Dimension
Allows analysis of a quantity by the rational powers of the 7 fundamental
dimensions (quantities are compatible when they have the same
dimensions):
length (L), mass (M), time (T), electric charge (I), absolute temperature
(Θ), amount of substance (N) and luminous intensity (J)
Examples:
Speed = length/time - it’s dimensions are L=1,T=-1 (rest 0) (e.g. metre/second - ms-1)
Acceleration is speed/time (m/s/s or ms-2) L=1, T=-2
Force is mass x acceleration M x ((length/time)/time) or M=1, L=1, T=-2
Molar Entropy: M=1 L=2 T=−2 Θ=−1 N=−1 (trust me!)

14. @wernerkeil | @UnitAPI#JSR363 | #EclipseScience | #ECE2016
Quantity
A physical attribute of a thing. Something that can be measured and has
units. Compatible quantities have the same dimension…
Examples:
• Time
• Length
• Speed
• Amount of Substance
• Luminous Intensity
• Volume
• Mass
• Force
• Power
• Electrical Current
• Magnetic Flux Density
• Volumetric Flow Rate
• Fuel Economy*
• Percentage
• Eggs per carton
• Sheep per hour
• Bits and bytes …
… ∞

15. @wernerkeil | @UnitAPI#JSR363 | #EclipseScience | #ECE2016
What is the problem, in code?
int distance = 6089; //in ???
float speed = airplane.getSpeed(); //in ???
System.out.println(“TTD: “ + (distance/speed) + “
hours”);
6,089 ??????
A Measurement
A Unit

16. @wernerkeil | @UnitAPI#JSR363 | #EclipseScience | #ECE2016
What is JSR-363, in code?
Airplane airplane = new Airplane(“A380”);
QuantityFactory<Length> lengthFactory =
provider.getQuantityFactory(Length.class);
Quantity<Length> distance = lengthFactory.create(6089d,
KILO(METRE));
Quantity<Speed> airplaneSpeed = airplane.getSpeed();
Quantity<Time> timeToDest = distance.divide(airplaneSpeed)
.asType(Time.class);
System.out.println(“TTD: “ + timeToDest.to(HOUR));
TTD: 6.443381088681372 h

17. @wernerkeil | @UnitAPI#JSR363 | #EclipseScience | #ECE2016
Who is going to use JSR-363?
Java developers who work with physical quantities need to handle
measurements in their programs.
Inadequate models of physical measurements can lead to significant
programmatic errors.
Platform providers and developers can provide and use a better defined
API
Embedded developers can have less error-prone, more self-
documented code

18. @YourTwitterHandle#DVXFR14{session hashtag} @wernerkeil | @UnitAPI#JSR363 | #EclipseScience | #ECE2016

19. @wernerkeil | @UnitAPI#JSR363 | #EclipseScience | #ECE2016
JSR-363 timeline
March 11, 2014: Submitted
April 7, 2014: Creation approved
Dec 2014 – Jan 2015: Early Draft (approved)
Nov 2015 – Jan 2016: Public Review (approved)
Q3/2016 : Final Draft
Q3/2016: Final Release

20. @wernerkeil | @UnitAPI#JSR363 | #EclipseScience | #ECE2016
Links to JSR-363
Public mailing list(s) / forum(s)
Units-Dev on Google Groups:
https://groups.google.com/forum/#!forum/units-dev
Units-Users on Google Groups:
https://groups.google.com/forum/#!forum/units-users
The JSR page on JCP.org: https://jcp.org/en/jsr/detail?id=363
Project website on GitHub: unitsofmeasurement.github.io
Get sample code from our GitHub repositories on
https://github.com/unitsofmeasurement/uom-demos.

21. @YourTwitterHandle#DVXFR14{session hashtag} @wernerkeil | @UnitAPI#JSR363 | #EclipseScience | #ECE2016

22. @YourTwitterHandle#DVXFR14{session hashtag} @wernerkeil | @UnitAPI#JSR363 | #EclipseScience | #ECE2016