Kernel Modeling Language (KerML) 1.1 RTF — Open Issues - OMG Issue Tracker

Key: KERML11-213

Status: open

Source: P-1 AI ( Ethan Lew)

Summary:

The result expression of VectorFunctions::'cartesian-' applies CartesianVectorOf twice, so it does not compute the difference of two vectors (or the negation of one).

Specification p. 394 and library model (SysML-v2-Release 2026-08, Kernel Libraries/Kernel Function Library/VectorFunctions.kerml, line 222):

function 'cartesian-' specializes '-' {
    in v: CartesianVectorValue[1];
    in w: CartesianVectorValue[0..1];
    inv precondition { w != null implies v.dimension == w.dimension }
    return u: CartesianVectorValue[1] =
        CartesianVectorOf(
            if w == null? CartesianVectorOf(v.elements->collect{in x : Real; -x})
            else CartesianVectorOf(
                (1..v.dimension)->collect{in i : Positive; v#(i) - w#(i)}
            )
        );
}

Both branches of the if already construct a CartesianVectorValue. The outer CartesianVectorOf(...) then takes that vector as its components, which are declared Real[*], so the argument does not conform. Read literally, the result is a one-dimensional vector whose single element is the difference vector. Every v - w and -v on Cartesian vectors is affected. The neighbouring 'cartesian+' has no such outer wrapper.

Example:

package Repro {
    private import VectorFunctions::*;
    attribute d = CartesianVectorOf((1.0, 2.0)) - CartesianVectorOf((3.0, 5.0));
    // expected: elements (-2.0, -3.0), dimension 2
    // as defined: dimension 1, and the one element is a CartesianVectorValue, not a Real
}

Proposed resolution: remove the outer CartesianVectorOf:

return u: CartesianVectorValue[1] =
    if w == null? CartesianVectorOf(v.elements->collect{in x : Real; -x})
    else CartesianVectorOf(
        (1..v.dimension)->collect{in i : Positive; v#(i) - w#(i)}
    );

Reported: KerML 1.0b4 — Sun, 18 Oct 2026 04:35 GMT

Updated: Tue, 20 Oct 2026 18:42 GMT