X-Received: by 10.224.217.195 with SMTP id hn3mr30156685qab.5.1367773346343; Sun, 05 May 2013 10:02:26 -0700 (PDT) X-Received: by 10.49.37.39 with SMTP id v7mr1427389qej.27.1367773346328; Sun, 05 May 2013 10:02:26 -0700 (PDT) Path: news.cambrium.nl!textnews.cambrium.nl!feeder1.cambriumusenet.nl!feed.tweaknews.nl!209.85.216.87.MISMATCH!l3no2401407qak.0!news-out.google.com!y6ni0qax.0!nntp.google.com!m7no2430327qam.0!postnews.google.com!glegroupsg2000goo.googlegroups.com!not-for-mail Newsgroups: comp.databases.theory Date: Sun, 5 May 2013 10:02:26 -0700 (PDT) In-Reply-To: Complaints-To: groups-abuse@google.com Injection-Info: glegroupsg2000goo.googlegroups.com; posting-host=79.164.43.178; posting-account=HyT01AoAAABE6CONnHE4NnFiYtoWAdfY NNTP-Posting-Host: 79.164.43.178 References: <515dc4c8$0$6066$e4fe514c@dreader36.news.xs4all.nl> <43eee84c-61eb-41cd-87bd-a7cf13a46c82@googlegroups.com> <6bbcbec3-adb2-4014-aa5a-f89f66d5c29b@googlegroups.com> <15eccbc4-b53a-4196-91b2-011ac4f91012@f18g2000vbs.googlegroups.com> <74b5393d-a532-4960-ab28-278772b8a013@googlegroups.com> User-Agent: G2/1.0 MIME-Version: 1.0 Message-ID: <13303797-7866-4981-85fa-69e962b995fe@googlegroups.com> Subject: Re: The same simple question to relational theorist (with video now). From: Evgeniy Grigoriev Injection-Date: Sun, 05 May 2013 17:02:26 +0000 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Xref: news.cambrium.nl > The query results in your examples often show empty cells. If their cont= ents are something like NULL, then no, your system can almost by definition= not be relational. 1) E.g. in http://www.dcs.warwick.ac.uk/~hugh/TTM/Missing-info-without-null= s.pdf on page 7 there is a question "BUT WHAT DO THOSE QUESTION MARKS MEAN?= ". I don't try to go in meaning of the empty cell so deeply. It's just emp= ty cells. 2)I could say that an implementation of my solution is as relational as usi= ng executive machine is. If we are using "true relational" system as execut= ive machine the result will be perfect theoretically. If we are using SQL D= BMS the result will possible contains NULL, dublicates etc. Offered princip= les can be applied to both "true" and "not true" relational systems. 3) 3-valued SQL logic is a very old question. It's intrestiong question but= it's not principial for me. My solution could appear 25 years back on that= level of relational theory and OO programing. For me a most hard thing was= to forget about all complicated things and ideas which appeared since that= time. > The system seems to be based on hierarchies of classes. That makes me wo= nder about situations where there are self-references (boss of employee3 is= employee2, boss of employee2 is employee7, ...) and transitive closures in= the processing. I dont' implement transitive closures cases in the prototype. Common idea l= ooks like=20 CREATE CLASS EMPLOYEE { name...; } CREATE CLASS BOSS EXTENDS EMPLOYEE { employees SET OF EMPLOYEE; } SELECT #b.employees.name FROM BOSS #b... THROUGH #b.employees... DOWN #b.name=3D"MainBoss" //"THROUGH" checks if some of "b.employees" are BOSSes=20 // and executes SELECT again for found ones. // "DOWN" sets "starting point" in BOSS'es hierarchy. This query returns names of all employee under "MainBoss". (Don't be stri= ct it's just a concept:) =20 > I'm wondering how transactions/commit/rollback fit into the system. If t= here is "autocommit" upon each NEW GOODS() executed, then I wonder about th= e situations that require SQL users to switch over to deferred constraint c= hecking. (And if there is no possibility to declare constraints, then no, = what you've created is not worth being called a DBMS. But I rather doubt t= his is the case.) 1) Transaction is not a question between OO and RM. :) 2) I don't understand what does "deferred constraints" mean here. 3) I gave an examples of constrains in video (from ~4:00). Could you explay= m your question in more details with these contrains if it's possible? > You also use the term "inheritance" in connection with your classes, but = it is unclear to me what "inheritance" really means here, or how it could b= e useful to me as a user of this system. Object domain can change and, according to the changes, you can create new = classes (inc. by multiple inheritance) in active DBMS. There is no necessit= y to rebuild, recompile, reload and make other re- over system in this case= , just create new class and you can use it with existing ones. You could = see the video after 19 min once again. I gave an example of how the system = can be extended by means of multiple inheritance.=20