Sorry about that. Yes, you need an identifier for each survey. You cannot use v000 for that purpose, because it can happen that DHS does two surveys in the same country with the same version of the core questionnaire. (The third character of v000 is often taken to be the phase of DHS--that's what I thought until relatively recently--but it actually identifies the version of the questionnaire.) You can find many instances of two successive surveys in the same country having the same value of v000. It is best to construct a unique identifier for each survey, as you describe. That's what I meant by "survey" in that line.