[Termtools] CPF/CeTA: split for relative termination?

Dear all, (sIsEmpty works fine, thanks René) can CPF/CeTA do "split" for relative termination? "split" can be used as a notational trick, to avoid unlabeling split for full termination is: SN(D / R-D) && SN(R-D) => SN(R) (application: semantic labeling in the first premise) http://cl2-informatik.uibk.ac.at/rewriting/mercurial.cgi/IsaFoR/file/1f1ecb1... I think I want SN(D / R+S) && SN(R-D / S-D) => SN(R/S) (cf. Geser "Relative Termination" (UIB 91-03) Section 3.2) but I cannot get CeTA to accept this, https://gitlab.imn.htwk-leipzig.de/waldmann/pure-matchbox/-/issues/489 - Johannes.