Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uunet!cimshop!davidm From: cimshop!davidm@uunet.UU.NET (David S. Masterson) Newsgroups: comp.databases Subject: Re: Comment on the "Third-Generation Database System Manifesto" Message-ID: Date: 24 Sep 90 17:44:03 GMT References: <21178@hercules.csl.sri.com> <1990Sep24.071412.3561@odi.com> Sender: davidm@cimshop.UUCP Distribution: comp Organization: Consilium Inc., Mountain View, California. Lines: 46 In-reply-to: dlw@odi.com's message of 24 Sep 90 07:14:12 GMT In article <1990Sep24.071412.3561@odi.com> dlw@odi.com (Dan Weinreb) writes: In article (I) write: Actually, the immutable, system-assigned primary key was a central part of the Codd/Date RM/T model (Date's Introduction to Database Systems V2), so the UID concept doesn't disagree with the relational model. Well, the RM/T model is not the same thing as the Relational model. The people are the same (so to speak) but RM/T is a distinct model, with new elements (such as the system-assigned primary key) designed to remedy some problems of the relational model. The OODB's also provide the equivalent of a system-assigned primary key. This is an interesting point. Is the contention, therefore, that the current relational implementations are representative of the relational model? Codd seems to contend that no one has yet implemented even RMV1 (let alone RM/T), but all these versions go into the definition of the relational model. Your paragraph seems to suggest that the current implementations are representative of the relational model and Codd's 12 rules (and 300+ newer rules) are something entirely new. A relational system can take advantage of the same clustering idea. "Time consuming optimizations", IMHO, are in the eye of the beholder. An OODB wouldn't have the full understanding of relationships that can occur in a database and, so, couldn't take advantage of a recursive join operation (unless the OODB was a relational DB). And why wouldn't an OODB have a full understanding of relationships? Your paragraph above must be read in the light of some understanding of "what is an OODB" and "what is a relational DB". You say that it can't have understanding unless it is a relational DB. Do you seriously mean that it has to follow Codd's Rules or else such an optimization is impossible? I suspect you mean something less stringent. Is what you mean incompatible with the definition of OODB, as given in the OODB manifesto? No it isn't. Looking at it now, my paragraph was more stringent than I wanted it to be. What I meant was that, when you get down to it, considerations such as these can be accomplished by both the OODB and the relational DB, so there really may not be that much of a difference between the two. -- ==================================================================== David Masterson Consilium, Inc. uunet!cimshop!davidm Mtn. View, CA 94043 ==================================================================== "If someone thinks they know what I said, then I didn't say it!"