Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uunet!odi!dlw From: dlw@odi.com (Dan Weinreb) Newsgroups: comp.databases Subject: Re: Comment on the "Third-Generation Database System Manifesto" Message-ID: <1990Sep25.231521.20697@odi.com> Date: 25 Sep 90 23:15:21 GMT References: <21178@hercules.csl.sri.com> <1990Sep24.071412.3561@odi.com> Reply-To: dlw@odi.com Distribution: comp Organization: Object Design, Inc. Lines: 37 In-Reply-To: cimshop!davidm@uunet.UU.NET's message of 24 Sep 90 17:44:03 GMT In article cimshop!davidm@uunet.UU.NET (David S. Masterson) writes: In article <1990Sep24.071412.3561@odi.com> dlw@odi.com (Dan Weinreb) writes: 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. Sorry, I don't follow this at all. I must be misunderstanding you. I don't see why you think I am suggesting what you said. What I am saying is that RM/T is quite disinct from what is usually called "relational". Current "relational database system" products do not exactly implement the Relational Model, but they are a lot close to the Relational Model than to RM/T. From my reading of Codd, the "12 rules" are an attempt to be more precise about the meaning of the Relational Model, whereas RM/T is a new proposed data model that is based on the Relational Model but has several crucial changes, considered to be improvements. Anyway, this was just a minor point; it didn't have much to do with the original issue under discussion. 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. I agree that the differences between the two are often exaggerated. When you look closely, they aren't as different as they seem at first.