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Eclipse UOMo

Eclipse Juno Demo Camp

Manchester, UK

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What is it?

Units of Measurement API

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Avoiding Interface�and Arithmetic Errors

The Goal

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Emphasis

Most of today’s technologies including the Java Language so far lack support for common non-trivial Arithmetic problems like Unit Conversions

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What do these disasters have in common?

Patriot Missile�The cause was an inaccurate calculation of the time since boot due to a computer arithmetic error.
Ariane 5 Explosion�The floating point number which a value was converted from had a value greater than what would be represented by a 16 bit signed integer.

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What do these disasters have in common?

Gimli Glider (near miss)�Fuel loading was miscalculated through misunderstanding of the recently adopted Metric System, replacing the Imperial System
Mars Orbiter �Preliminary findings indicate that one team used English units (e.g. inches, feet and pounds) while the other used metric units for a key spacecraft operation.

NASA lost a $125 million Mars orbiter because a Lockheed Martin engineering team used English units of measurement while the agency's team used the more conventional metric system for a key spacecraft operation
This also underlines the added risk when 3^rd party contractors are involved or projects are developed Offshore

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NASA “Star Wars” Initiative, 1983

23^rd March 1983. Ronald Reagan announces SDI (or “Star Wars”): ground-based and space-based systems to protect the US from attack by strategic nuclear ballistic missiles.

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1985

Mirror on underside of shuttle

SDI Experiment: The Plan

Big mountain in Hawaii

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1985

SDI Experiment: What really happened

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1985: What happened?

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Unit Tests wouldn‘t find these…

All previous example illustrate three categories of errors difficult to find through Unit Testing:

Interface Errors (e.g. millisecond/second, radian/degree, meters/feet).
Arithmetic Errors (e.g. overflow).
Conversion Errors (e.g. wrong factors or rounding)

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Causes of Conversion Errors

Ambiguity on the unit

Gallon Dry / Gallon Liquid
Gallon US / Gallon UK
Day Sidereal / Day Calendar
...�

Wrong conversion factors:

static final double PIXEL_TO_INCH = 1 / 72;

double pixels = inches * PIXEL_TO_INCH

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Eclipse UOMo

One Small Step…

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Eclipse UOMo

Namespace: org.eclipse.uomo.*
Two main areas

Static Type Safe Units of Measure Support

Based on Units of Measurement API
On top of ICU4J, the Globalization standard at Eclipse and others (Android, GWT, Google Financial, etc.)

Prime UCUM Implementation

Successor to Eclipse OHF UCUM Bundle

One Unit Framework to Measure them All

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Eclipse UOMo

UOMo currently consists of

UOMo Core

General parts of the framework, reusable components

UOMo Util

Utility classes, Formatting, Date/Time and other ICU4J or Unicode related items

UOMo XML

XMLPull and support for Markup Languages like UnitsML, MathML or SensorML

Bundles

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Eclipse UOMo

UOMo Units

Based on Units of Measurement API

UOMo UCUM

Unified Code for Units of Measure support

UOMo Business

Business Types and Monetary System

Bundles (2)

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UOMo: UCUM

The Unified Code for Units of Measure is a code system intended to include all units of measures being contemporarily used in international science, engineering, and business.
The purpose is to facilitate unambiguous electronic communication of quantities together with their units.
The focus is on electronic communication, as opposed to communication between humans.
A typical application of The Unified Code for Units of Measure are electronic data interchange (EDI) protocols, but there is nothing that prevents it from being used in other types of machine communication (e.g. persistence).

Unified Code for Units of Measure

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UOMo: UCUM Examples

UCUM String	Human Unit	Quantity
m/s	Meter per second	Length
%	Percent	None
[tbs_us]	Tablespoon (US)	Volume
mm2	Square Millimeter	Area
mL/kg/h	Millilitre per Kilogram per hour	Dose
cm[H2O]/(s.m)	Centimeter H20 per second and meter	Pulmonary pressure time product