Re: Informal Survey #1 -- joins on foreign keys
Date: Sun, 29 Apr 2012 11:12:06 -0700 (PDT)
Message-ID: <26514096.155.1335723126413.JavaMail.geo-discussion-forums_at_ynek6>
Dana utorak, 10. travnja 2012. 00:49:44 UTC+2, korisnik com..._at_hotmail.com napisao je:
> On Wednesday, 4 April 2012 16:06:47 UTC-7, vldm10 wrote:
>
> > We do not understand one another regarding some important issues.
>
> Unfortunately you don't understand my references to many that are basic, simple and common in logic and mathematics.
>
> > I also think that you pay attention only to the model. However db also works with real word objects.
>
> Predicate logic wffs and relational expressions correspond. Each connects the database to the world by its predicate extensions holding the tuples of values giving true propositions. Thus every predicate and relation expression connects the database and the world. Other connection is unnecessary. (Though perhaps useful.) I have explained that a foreign key asserts that certain tuple subsetting occurs and that correspondingly a certain implication holds in the world. (About entities, if you wish). Sorry I haven't been able to make this or much else clear for you. Sorry but your papers are mostly incomprehensible and they misunderstand the RM.
>
> philip
Received on Sun Apr 29 2012 - 20:12:06 CEST