How JSR 385 could have Saved the Mars Climate Orbiter DevoxxUA 2019
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The document discusses the Mars Climate Orbiter mission, which failed due to a mix-up between metric and imperial units. It suggests that using JSR-385, a Java specification request for a units of measurement API, could have prevented this error. JSR-385 provides a standard library for defining and working with physical quantities and units that avoids issues with primitive types. The document provides an overview of key concepts in JSR-385 like dimensions, units, quantities, and systems of units.
How JSR 385 could have Saved the Mars Climate Orbiter DevoxxUA 2019
- 1. How JSR-385 could have Saved the Mars Climate Orbiter Werner Keil & Thodoris Bais @thodorisbais@wernerkeil
- 4. Mars Climate Orbiter • Launched on 11 December 1998 • 338 kilograms • $125 millions • To study Martian climate, atmosphere and surface changes @thodorisbais@wernerkeil
- 5. Result of the Mission @thodorisbais@wernerkeil
- 8. Mars Climate Orbiter “The problem here was not the error; it was the failure of NASA’s systems engineering, and the checks and balances in our process, to detect the error. That’s why we lost the spacecraft.” Edward Weiler NASA associate administrator of space science, IEEE Spectrum: Why the Mars Probe went off course @thodorisbais@wernerkeil
- 9. Lessons Learned @thodorisbais@wernerkeil •Read the software specifications •Use JSR-385 instead of primitives •Fail-fast
- 12. What is the Fundamental Problem? Primitive (Java) types are primitive types @thodorisbais@wernerkeil
- 13. What is the Fundamental Problem? Primitive (Java) types are primitive types • static final double C = 1079252849; • static final double SPEED_OF_LIGHT = 1079252849; • static final double SPEED_OF_LIGHT_IN_KM_PER_H = 1079252849; @thodorisbais@wernerkeil static final Quantity<SPEED> SPEED_OF_LIGHT = Quantities.getQuantity(1079252849, Units.KILOMETRE_PER_HOUR);
- 14. Rolling your Own Library • Development • Maintenance • Upgrades & extensions @thodorisbais@wernerkeil
- 15. Werner Keil Thodoris Bais Spec Lead JSR-385 Expert Group Member JSR-385 Let’s meet @thodorisbais@wernerkeil
- 17. @thodorisbais@wernerkeil JSR-385: Units of Measurement API 2.0 JSR-363 Modularity Support Java SE >=8
- 18. JSR-385 Basic Concepts • Dimensions • Units • Quantities • Prefixes • Converters • Formats • Systems of units @thodorisbais@wernerkeil
- 20. Write a program to calculate the BMI of a person Exercise description BMI is a person's weight in kilograms (kg) divided by his or her height in meters squared @thodorisbais@wernerkeil
- 21. Setting up a project <dependencies> <dependency> <groupId>tech.units</groupId> <artifactId>indriya</artifactId> <version>2.0.1</version> </dependency> </dependencies> @thodorisbais@wernerkeil
- 23. –Wikipedia “A physical quantity is a physical property of a phenomenon, body, or substance, that can be quantified by measurement.” Definition of a Physical Quantity @thodorisbais@wernerkeil
- 24. Speed of Light c = 299,792,458 m/s Value Unit @thodorisbais@wernerkeil
- 25. One more quote @thodorisbais@wernerkeil –Ibidem “The same physical quantity can be represented equivalently in many unit systems.”
- 26. Speed of Light c = 299,792,458 m/s = 1,079,252,849 km/h @thodorisbais@wernerkeil
- 27. 1. Define two quantities a. A mass b. A length 2. Print them out Exercise Time @thodorisbais@wernerkeil
- 28. •Divide the mass by the square of the height •Print out the result Exercise Time @thodorisbais@wernerkeil
- 32. Multiples • km • ms • Mm? • ks? @thodorisbais@wernerkeil
- 34. Dimensions • L: length • T: time • M: mass • I: electric current • Θ: thermodynamic temperature • N: amount of substance • J: luminous intensity • (1) Force: L · M · T-2 @thodorisbais@wernerkeil
- 37. Equality and Equivalence • kΩ ≠ mHz • kΩ ≠ mΩ • kΩ ≡ kΩ • N ≅ kg·m·s-2 • kg·m-2 ≅ mg·mm-2 • 1 kΩ ≠ 1 mHz • 1 kΩ ≠ 1 mΩ • 1 kΩ ≡ 1 kΩ • 1 N ≅ 1 kg·m·s-2 • 1 kg·m-2 ≅ 1 mg·mm-2 • 1 kΩ ≅ 1,000 Ω Units Quantities @thodorisbais@wernerkeil
- 38. Quantity Addition • 1 Ω + 1 Ω = 2 Ω • 1 Ω + 1 mΩ = 1.001 Ω • 1 mΩ + 1 Ω = 1,001 mΩ • 1 Ω + 1 m “does not compile” @thodorisbais@wernerkeil
- 39. DevoxxUA School November Exam on Maths How much is 0 °C + 0 °C? • 0 °C • 0 °C • 273.15 °C Two absolute temperatures 0 °C + 0 °C = 273.15K + 273.15K = 546.30K = 273.15 °C @thodorisbais@wernerkeil
- 40. How much is 0 °C + 0 °C? • 0 °C • 0 °C • 273.15 °C An absolute temperature and a temperature change 0 °C + 0 °C = 273.15K + 0K = 273.15K = 0 °C @thodorisbais@wernerkeil DevoxxUA School November Exam on Maths
- 41. How much is 0 °C + 0 °C? • 0 °C • 0 °C • 273.15 °C Two temperature changes 0 °C + 0 °C = 0K + 0K = 0K = 0 °C @thodorisbais@wernerkeil DevoxxUA School November Exam on Maths
- 42. How much is 0 °C + 0 °C? 273.15 °C (546.30 K) 0 °C + 0 °C = 0 °C (273.15 K) 0 °C (0 K) Answer @thodorisbais@wernerkeil DevoxxUA School November Exam on Maths
- 43. Multiplication Units •kg × m = kg·m •kg × mm = kg·mm •g × km = g·km ≟ kg·m •m × m = m2 •km × km = km2 •mm × km = mm·km ≟ m2 •µm × m = µm·m ≟ mm2 Quantities •2 kg × 3 m = 6 kg·m @thodorisbais@wernerkeil DevoxxUA School November Exam on Maths
- 44. Division Units •kg / m = kg·m-1 •kg / mm = kg·mm-1 •g / mm = g·mm-1 ≟ kg·m-1 •m2 / m = m •m / m = 1 •km / km = 1 •km / m = km/m ≟ 1k Quantities • 3 kg / 2 m = 1.5 kg·m-1 @thodorisbais@wernerkeil DevoxxUA School November Exam on Maths
- 45. Powers Units •(m)2 = m2 •(km)2 = km2 •(m2)2 = m4 Quantities • (3 m)2 = 9 m2 • @thodorisbais@wernerkeil DevoxxUA School November Exam on Maths
- 46. Celsius Revisited Units •(K)2 = K2 •(°C)2 ≟ (K - 273.15)2 •m × °C ≟ m·(K - 273.15) Quantities •0 °C2 ≟ 74,610.9225 K2 •1 m°C ≟ 1 mK or 273.151K @thodorisbais@wernerkeil DevoxxUA School November Exam on Maths
- 47. Parsing Units & Quantities •299,792,458 m/s •299792458 m/s •299792.458 km/s •299,792.458 km/s •299,792,458 km*s-1 • 299,792.458 km×s-1 •299,792.458 km·s-1 •299,792.458 km·s⁻¹ •299,792.458 km*s^-1 •1,079,252,849 km/h •1,079,252,849 km/t • 670,616,629 mph Speed of Light @thodorisbais@wernerkeil
- 48. Systems of Unit Systems of UnitSystems of Unit • Metric System • Imperial System • US customary units • Roman units of measurement •Norwegian Units of Measurement @thodorisbais@wernerkeil
- 50. What Was the Fundamental Problem Again? Primitive (Java) types are primitive types @thodorisbais@wernerkeil
- 51. JSR-385 Current Status • JCP page • https://jcp.org/en/jsr/detail?id=385 • GitHub repositories • https://github.com/unitsofmeasurement • Current status • Final Release @thodorisbais@wernerkeil
- 53. @thodorisbais@wernerkeil We’re running for an Associate Seat!
- 54. Becoming a JCP Member @thodorisbais@wernerkeil