Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!crdgw1!uunet!vtserf!creatures!csgrad!holliday From: holliday@csgrad.cs.vt.edu Newsgroups: comp.databases Subject: Re: Looking for ERA databases Message-ID: <1058@creatures.cs.vt.edu> Date: 23 Mar 91 17:48:07 GMT References: <4821@berry7.UUCP> Sender: usenet@creatures.cs.vt.edu Reply-To: holliday@csgrad.cs.vt.edu () Distribution: comp Organization: Virginia Tech Computer Science, Blacksburg, VA Lines: 28 In article cimshop!davidm@uunet.UU.NET (David S. Masterson) writes: >>>>>> On 12 Mar 91 21:23:14 GMT, saxena@motcid.UUCP (Garurank P. Saxena) said: >Garurank> We are looking for a database which supports the Entity-Relationship >Garurank> (ERA ) model. Other requirements from the database would be > >Garurank> Are there commercial or prototype ER databases available? > >Isn't ER just a modeling for relational databases? Therefore, don't all >relational databases support the ER(A) model by definition? BTW, what do you >mean by "schema evolution"? >David Masterson Consilium, Inc. No - ERA is often used to help design relational layouts, but these methods end up converting from ERA to relational tables. As data models, they are 2 different things. I am only aware of 2 full-fledged ERA databases. One is PSA, from MetaSystems, Ann Arbor. It's been sold in various forms since the 70s, descending from ERA research at U of Mich, and shows its age. The second is Camera, from ASTEC in Greenbelt MD, which is marketed as a direct competitor to PSA. -- Glenn | holliday@csgrad.cs.vt.edu OR Holliday | glenn%bayberry@chado.fidonet.org OR | GHOLLID@access.nswc.navy.mil (Internet)