APPE.

Adobe's licensed PDF rendering core, which most commercial RIPs (Caldera and ColorGATE among them) build on instead of writing their own PDF interpreter. When a RIP release leads with an APPE version number, that number describes the shared engine underneath, not the vendor's own code. Two RIPs on the same APPE build rasterize a PDF the same way; the difference between them is the workflow wrapped around it.