Re: What are units-of-measure? e.g., what's a "kilometer"?
John Cowan wrote: > > 2. Is kilometer a function? e.g., kilometer(Yangtze) --> 6300 > > In general: kilometer(physical object) --> number > > "The kilometer function maps a physical object to a number." > > I think this view is the most nearly correct, but it needs amplification: > it doesn't capture that it's the *length* (rather than, say, the > average depth) of the Yangzi that is 6300 km. So we can rewrite it > in terms of relations as follows: > > Yangzi length X > X kilometer 6300 > > where "kilometer" is a relation that maps a length (an abstract property > of a physical object) into a pure number. So, kilometer is a function of this sort: kilometer(length(Yangtze)) --> 6300 "kilometer is a function which maps the length of the Yangtze to 6300." Another example: kilometer(avg-depth(Yangtze)) --> 0.25 "kilometer is a function which maps the average depth of the Yangtze to 0.25." The general case is: kilometer(distance) --> number where distance is an abstract dimension object. How are functions represented syntactically in XML? Given the above viewpoint, this form no longer seems appropriate: <River id="Yangtze"> <length units="kilometer">6300</length> </River Perhaps a more faithful representation of: kilometer(length(Yangtze)) --> 6300 is this: <River id="Yangtze"> <length> <kilometer>6300</kilometer> </length> </River> Thoughts? /Roger
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