[om] DefMP elements

[Bill Naylor]

> > >As to the fourth:
> > >d) use signatures in definitions: this might prevent a definition from
> > >being misapplied in an application that doesn't know any better. This
> > >may well be done in the simple way of using universal quantifiers and
> > >set memberships inside the defining FMPs, so that this may simply be
> > >added as a recommendation to CD writers.
> But the symbol being defined has a signature in STS, which is why the sin
> on matrices is not the sin from transc1.
> James

Excuse me for appearing a bit ignorant here. The signature for sin in STS
is defined as sin: NumericalValue -> NumericalValue, where NumericalValue
is defined as:

"NumericalValue

Denotes an OpenMath object that is to be thought of as something that
represents a numerical value, or a numerical value."

this seems very circular to me, where do we define a 'numerical value'? I
mean integers are clearly numerical values, so are reals. Almost as
clearly complex numbers are numerical values. What about Quaternions? I
would have thought so? What is it that makes them numerical and matrices
not?

thoughts?

Bill.

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