The clause lists the abbreviations the draft uses. The DIS adds solid state disk and write once read many storage to the earlier list, which is a small but useful signal that removable and optical media are no longer the only carriers in view. Clause 4 looks trivial and is not. Every deletion procedure ends in a storage medium, and the medium decides what a defensible deletion looks like. A write once medium cannot be overwritten in place, so the procedure has to destroy it, retire it or rely on encryption with key destruction. A solid state device does not behave like a magnetic disk when a block is rewritten, because wear levelling can leave copies behind. The draft's own scope keeps mechanisms out, so clause 4 is not the place to solve that. It is the place where the shared words are fixed so that the later clauses can talk about media without ambiguity. For a reader comparing editions, the addition of the two storage terms is one of the visible signs that the revision has been touched up for current infrastructure. It does not by itself change an obligation, but it changes the checklist a team should use when it inventories where records live. A deletion framework that still lists only discs, tapes and drives is likely to have a blind spot in the laptop and data centre estate.
The graph holds this control, the 0 it maps to, and the evidence behind each claim, over MCP and REST.