This method checks whether the local ring was produced by localization at a prime ideal.
i1 : R = QQ[x,y,z,w] o1 = R o1 : PolynomialRing
i2 : P = ideal"xz-y2,yw-z2,xw-yz"; -- The twisted cubic curve o2 : Ideal of R
i3 : isWellDefined R_P o3 = true
i4 : Q = ideal"xz-y2,z(yw-z2)-w(xw-yz)"; o4 : Ideal of R
i5 : isWellDefined R_Q o5 = false