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Re: Other experts
- From: Leonardo Lima <
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- To: "
" <
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- Subject: Re: Other experts
- Date: Fri, 17 Oct 2014 13:42:33 -0300
Werner,
I didn't get it. Did you propose Eclipse to join our JSR as EG member or
not?
Regards,
Leonardo.
On Fri, Oct 17, 2014 at 11:09 AM, Werner Keil
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wrote:
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Leo/all,
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Thanks for the message. Will briefly reply both, you mostly quoted
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Otavio's or Martin's recent thread, but may have seen my caveat about the
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judgment and design conflicts between various ends of the JDK as early as
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JDK 1.x or Java 5. When it was officially still done by Sun alone, but
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especially things like Date/Calendar came from a planned IBM/Apple(!) joint
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venture named Taligent/Pink, which few pieces left turned into OTI, a group
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that created large portions of Eclipse;-)
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Speaking of which, the IoT project there is interested, and we should
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involve them or other users (including Jean-Marie, whether JScience or
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Embedded/Realtime Java usage at Airbus, those are also are users who'd
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implement the API more likely than using the RI;-) but not every
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"downstream" user will want to join the EG, too. I'm not even sure, if
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their company is still a JCP member?
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Many feel happy if Eclipse represents them as a whole;-)
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Unlike the use of JSR-275 by GeoAPI (lead and represented by Martin) so
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far there are solutions and implementations like JScience or UOMo (already
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at Eclipse) offering such arithmetic on an implementation level alone.
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There are not too many serious Unit libraries, if you Google it with Java
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you'll find this JSR beside 275 or JScience first;-)
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Something notable for Ada, but the language may allow things, Java doesn't
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http://www.dmitry-kazakov.de/ada/units.htm
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The basic terms are similar, as for most languages, simply because almost
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every of them relates to Andrew Kennedy's papers;-)
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Kawa (note the Lambda;-) is a powerful GNU environment for Java over 10
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years old
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http://www.gnu.org/software/kawa/Quantities.html
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It was around, when the EG of JSR 108 eventually withdrew the JSR. And
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without having been on board then I assume, it was because of similar
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disputes and discussions;-O
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In Kawa you can pretty much do anything and you normally get a result.
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Errors at most are thrown at runtime.
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OSGi Measurement, it certainly influenced the new approach a bit:
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http://www.osgi.org/javadoc/r4v42/org/osgi/util/measurement/Measurement.html
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Note all operations exist in the API except Measurement.invert()
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Which IMHO is the most questionable here, at least for Quantity. I'd be
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happy to drop that unless a large user base cries for it.
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OSGi Measurement checks everything at runtime. 1m.add(1kg) throws an
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exception, but although JavaDoc states there could be an
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ArithmeticException for Measurement.mul(Measurement), too, I have never
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seen one. And operations like:
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1kg.div(1sec) work fine and produce results like "1 kg/s" just like
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1km.div(1sec) shows "1 km/s" (Acceleration).
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I am not sure, if depriving users at least from basic operations (+-*/)
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like those defined by Fowler in his Quantity pattern would be good?;-)
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Otherwise several users might stick to Kawa or OSGi Measurement or simply
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reinvent the wheel;-/
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If an implementing class needs to throw a Runtime exception because e.g.
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"kg/s" was wrong, but "km/s" allowed in that context, then it'll do.
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If we wanted to enforce strict type safety, then similar to OpenXC there
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should be concrete classes for everything;-)
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http://android.openxcplatform.com/reference/com/openxc/measurements/Measurement.html
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On top of BaseMeasurement and Quantity. Note, there's no generic for a
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quantity type, only to ensure, numeric values are used and Quantity extends
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Unit, I hope nobody wants us to go there?;-D
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Unless the classes are final, one could declare a Meter.multiply(Meter)
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method in a subclass of Meter returning Liter.
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OpenXC has no intention of arithmetic support, even basic unit conversion
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is not supported. Probably a reason why practically no other vendor than
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Ford cares about it, not even in Europe?;-)
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Regards,
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Werner
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Am 17.10.2014 13:59 schrieb "Leonardo Lima"
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<
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Hello, Werner!
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> You mentioned you talked with Eclipse guys about they supporting this.
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> Why don't they join this JSR as Experts as well? Did you propose it to
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> them?
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> I think it would add value to the discussion, having other people with
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> explicit needs in this field.
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> Regards,
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> Leonardo.
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