Talk:Q47574

measured physical quantity: Dimension of physical quantity

A physical dimension (such as Mass) is measured by a unit of measurement (such as kilogram).
The idea was to model this as the inverse:
A "unit of measurement" has a "measured physical quantity" called a "Dimension of physical quantity".
But maybe there's a better way to do this (or none at all). DavRosen (talk) 15:17, 10 February 2017 (UTC)

Let's look at the International Vocabulary of Metrology

@Infovarius: If you look up item 1.19 in the International Vocabulary of Metrology, you will a number of examples of "values", the first of which is "EXAMPLE 1 Length of a given rod: 5.34 m or 534 cm". Since this publication comes from a reputable source, I am inclined to accept its definiton, namely that a "unit of measurement" is part of a "value" - after all there is a big difference between 5.34 and 534, yet, once the units are added, they both relate to the same value. Martinvl (talk) 21:57, 5 May 2017 (UTC)

@Infovarius: I am not happy with a "unit of measurement" being listed as a sub-class of a physical quantity. I can think of three valid sub-classes of physical quentities - scalar quantities (for example mass, energy), vector quantities (for example force, torque) and tensor quantities (for example stress). Furthermore, as discussed earlier, I still think that a "unit of measurement" is part of a "physical value", not a sub-class of a physical measurement. Martinvl (talk) 17:46, 7 May 2017 (UTC)

Martinvl's reasoning seems sound to me. Jc3s5h (talk) 00:18, 31 March 2018 (UTC)

Property removal

I ‎removed a claim: subclass of (P279): standard (Q1271511)). Standards sometimes are a method of defining a unit (e.g. kilogram). Other times they are an approximate implementation of a unit, useful in testing a less accurate implementation. (For example, in the past, a surveyor might have sent a high-quality surveying tape to a national laboratory where it would be laid upon a standard bench, equipped with metre marks, and a report would be issued describing how much the tape departed from the standard bench. Then the surveyor would store the tape in a safe place and use it periodically to test the length of tapes subjected to to the rough-and-tumble of field work.)

I do not think this reality fits the subclass of (P279) property. Jc3s5h (talk) 00:16, 31 March 2018 (UTC)

• No support or opposition at this time, just asking whether you have any idea what else could be used instead? The item needs a subclass of (P279) statement. —MisterSynergy (talk) 05:30, 31 March 2018 (UTC)
  • I added P279 measure (Q39875001), this seems clear, right? ArthurPSmith (talk) 13:22, 31 March 2018 (UTC)
    • I can't think of anything better than measure (Q39875001). Thanks. Jc3s5h (talk) 14:34, 31 March 2018 (UTC)

Work

I propose this as superclass as all units were invented ("created") by humans. Also it helps to bypass constraint violation for using based on (P144) in them. --Infovarius (talk) 16:01, 27 August 2020 (UTC)

You mean work (Q386724) (we have a lot of other things labeled "work")? artificial object (Q16686448) might be better, as generally a work would have a known creator, but I don't think that's generally the case for units. But maybe some do? ArthurPSmith (talk) 17:22, 27 August 2020 (UTC)

Some do for sure. Probably most recent units like becquerel (Q102573). Yes, Q386724. --Infovarius (talk) 15:50, 28 August 2020 (UTC)

Reading the short property proposal for based on (P144), for instance the comment "For example, book used for movie screenplay, or poem used by opera libretto.", this property is intended for creative works, not for any identifiable thing conceived by humans. Toni 001 (talk) 22:39, 27 August 2020 (UTC)

Yes, creative work (Q17537576) is a separate class and I don't think that units belong to it. But if they are not works how to model that pascal (Q44395) is defined ("derived") from newton (Q12438) and metre (Q11573) (or square metre (Q25343))? --Infovarius (talk) 15:50, 28 August 2020 (UTC)

Units are defined through their quantities. Quantities are either base quantities or defined through equations in terms of base quantities. Wikidata models this by linking units and quantities, and listing a defining equation with the quantity. Toni 001 (talk) 09:59, 30 August 2020 (UTC)

So where I can find equation pascal (Q44395) = newton (Q12438) / square metre (Q25343) (not in LaTeX but item form)? --Infovarius (talk) 13:42, 31 August 2020 (UTC)