SUO: RE: SUMO as a starter document
Unfortunately there are now 3 definitions of Exponent 10 in SUMO.
One is defined by kif as "expt 10". The other 2 are undefined.
"^" is used as exponent, but is defined as a meta operator in kif.
"E09" is undefined, but its meaning is clear to FORTRAN users.
The definitions of mega and other SI prefixes should be exponent 10
based.
For exponent 2 based notions like megabit, it is recommended by IEEE
standards coordinating committee , or whatever, to move to a new
prefix space ie kibi (Ki) , mebi (Mi), gibi (Gi) and tebi (Ti) to
avoid confusion (as noted in SUMO, but the 2-based notions are
substuted for mega there).
So a lot of work is needed just to encode SI in SUMO.
A proof that the job is done would be to be able to do
dimension checking on expressions. See the CellML mark up
language for an example of how an ontology can be used for
dimension checking in a real scientific application.
To really define a unit of measurement its necessary to define
at the same time a frame of reference of practices and institutions.
Calling a subontology a name like "SI" leaves these unstated.
It would be better to create a conglomerate like
"SI Frame of Reference", with traceability from the definitions
to the authoritative bodies (like NIST) and to the vendors of
the measuring equipment who must calibrate to certain tolerances.
Similar frames of reference are Universal Time Coordinated, and
geospatial datums.
>Yes but which still includes (for example) ...
>
>Nano-Second (constant id 452)
>
> Arg 1:
> (instance-of Nano-Second TimeMeasure-Duration)
> (instance-of Nano-Second UnitOfMeasure)
> (documentation Nano-Second "Submultiple of &%Second-Duration.
>Symbol: ns. A &%UnitOfMeasure equal to one billionth of a &%Second-
>Duration.")
>
> (equal (MeasureFn ?NUMBER Nano-Second) (MeasureFn
>(MultiplicationFn ?NUMBER 9.999999717180685E-10) Second))
>
>Surely something is wrong in the approach to representation if we
> are ending up with numerical error. Furthermore, I am not sure
>whether even the string "1E-9" would be "correct"? Where is the
>information that this is a definitional, exact multiplication factor
>(in contrast to the factors that are included for multiplication
>between metre and mile; by the way is the SI unit "meter"
>or "metre")? Where is the information that "Nano-" used with all
>other SI units carries the same definition? and so on ...
>
>As ever,
>Tim.
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