The NIST ontology defines 4 basic classes that are great:
_qudt:QuantityKind [11]_, _qudt:Quantity [12]_, _qudt:QuantityValue [13]_, _qudt:Unit [14]_
but the properties set leaves me a bit thirsty. Take "Area" as an example. I'd like to reference properties named .ft2 and .m2 so that, for instance, an annotation might be [[Leasable area.ft2::12345]]. To state the precision applicable to that measurement, might be [[Leasable area.ft2:fractionDigits :: 0]] to indicate say, rounding. However, in the NIST ontology, there is no "ft2" property at all -- this is an SI unit though, so it seems identifying first the system of measurement units, and then the specific measurement unit is not a great idea because these notations are then divorced from the property name itself, a scenario guaranteed to cause more user errors & omissions I think.
Someone's mentioned uncertainty facets, so I suggest these from the qudt ontology:
Property: .anyType:relativeStandardUncertainty Property: .anyType:standardUncertainty
Other facets noted might include
Property: .anyType:abbreviation Property: .anyType:description
Property: .anyType:symbol
-john
On 19.12.2012 08:10, Herman Bruyninckx wrote:
On Wed, 19 Dec 2012, Denny Vrandečić wrote:
Martynas, could you please let me know where RDF or any of the W3C standards covers topics like units, uncertainty, and their conversion. I would be very much interested in that.
NIST has created a standard
in OWL: "QUDT - Quantities, Units, Dimensions and Data Types in OWL and XML":
<http://www.qudt.org/qudt/owl/1.0.0/index.html [5]>
I fully
share Martynas' concerns: most of the problems that are being
discussed in this thread (and that are very relevant and interesting)
should not be solved with an "object oriented" approach (that is, via
properties of objects, and "inheritance") but by semantic modelling (that
is, "composition" of knowledge). For example, one single data
base
representation of a unit can have multiple "displays" depending
on who
wants to see the unit, and in which context; the viewer and the
context are
rather simple to add via semantic primitives. For example,
the "Topic Map"
semantic standard would fit here very well, in my
opinion:
<http://en.wikipedia.org/wiki/Topic_map [6]>.
Cheers,
Denny
Herman http://people.mech.kuleuven.be/~bruyninc%3E Tel: +32
16 328056 Vice-President Research euRobotics http://www.eu-robotics.net [7] Open RObot COntrol Software <http://www.orocos.org [8]> Associate Editor JOSER <http://www.joser.org [9]>, IJRR <http://www.ijrr.org [10]>
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