Like queries, updates too have the potential to be quite complicated in the temporal context. The chapter begins by considering updates on a database consisting of current relvars only (a comparatively straightforward case). It then considers databases consisting of historical relvars only; these investigations lead to a discussion of “U_updates,” PORTION specifications, and the need for a multiple form of assignment. It then considers databases containing both kinds of relvars. The chapter also discusses the possibility of using automatically defined views to simplify the formulation of such updates.
“temporal” update; PORTION; multiple assignment; current relvar; historical relvar; automated view
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