spaceship-test.n3

@prefix math: <http://www.w3.org/2000/10/swap/math#> .
@prefix nary: <http://gallows.inf.ed.ac.uk/schema/n-ary#> .

## a curried predicate embedding the kilogram unit
:massInKilograms a nary:BinaryRelation ;
    nary:reifiedType :MassObservation ;
    nary:subjectPredicate :system ;
    nary:objectPredicate :value ;
    nary:arg [
        nary:predicate :unit ;
        nary:object :kg
    ] .

## a curried predicate embedding the pounds unit
:massInPounds a nary:BinaryRelation ;
    nary:reifiedType :MassObservation ;
    nary:subjectPredicate :system ;
    nary:objectPredicate :value ;
    nary:arg [
        nary:predicate :unit ;
        nary:object :lb
    ] .

## a unit conversion description
[ 
    a :Conversion ;
    :fromUnit :kg ;
    :toUnit :lb ;
    :factor 2.2
] .

## a simplistic rule for converting units
{
    ?obs a :MassObservation ;
        :system ?sys ;
        :value ?val ;
        :unit ?unit .
    ?conv a :Conversion ;
        :fromUnit ?unit ;
        :toUnit ?toUnit ;
        :factor ?factor .
    (?val ?factor) math:prod ?toVal .
} => {
    [
        a :MassObservation ;
        :system ?sys ;
        :value ?toVal ;
        :unit ?toUnit
    ] .
} .

:s1 :massInKilograms 1000.0 .