Dale@tektronix.UUCP (01/30/86)
I am looking for a statement of the formal semantics of QBE. I have read the paper "Query-by-Example: a data base language" by M.M. Zloof (IBM Syst. J., #4, 1977) which is one of the early published descriptions of QBE. That paper presents QBE by means of (what else!) examples. That's sufficient for the easy cases, but I'm uncertain of the meaning of queries involving aggregates or (in Ingres terminology) aggregate functions. And queries that involve joins on sets are completely unclear to me. There is a paper entitled "Algorithm for Processing Query by Example" by Niebuhr et al (IBM Tech. Disc. Bull., vol. 19 #2) which helps a little, but assumes the reader already understands the semantics. Anyway, any pointers to papers will be muchly appreciated. Dale Brayden Scientific Computer Center, DS 50-454 Tektronix, Inc. P.O. Box 500 Beaverton, OR 97077