Re: Another view on analysis and ER
Date: Fri, 07 Dec 2007 13:27:14 GMT
Message-ID: <SSb6j.10853$3W.3518_at_trndny04>
"mAsterdam" <mAsterdam_at_vrijdag.org> wrote in message
news:475941b3$0$235$e4fe514c_at_news.xs4all.nl...
> Sorry for butting in this late, and not even completely on topic.
> 'Facts' triggered my interest.
>
> Jon Heggland schreef:
>
> > ...(The idea of viewing a database as a
> > collection of facts was a revelation for me in that regard.) In fact, I
> > have the opposite problem; I am unable to look at an E/R diagram without
> > thinking about relations.
> >
> > Consider this proposition: "Jon was born in 1974", encoded in a relvar
> > of the form Born(Person, Year). I think we'll agree that represents a
> > fact about Jon. You would probably assume that Jon is an entity (though
> > I'm unsure about what you'd call the relvar/predicate in itself---is it
> > an entity (type)?). But I would also say that the proposition is as much
> > a fact about the year 1974! Is 1974 an entity? I really don't care.
> > Facts are all.
>
> Consider the statement "Jon is 33 years old". It conveys the same real
> world fact in a clumsier way than "Jon was born in 1974". Next year it
> won't even convey the same fact anymore. "Jon was born in 1974"
> catches the invariant better than "Jon is 33 years old".
>
> Consider "John is in Canada". When? The fact isn't
> complete without that piece of information.
>
Time for a Clinton moment. The above discussion depends on what the meaning of the word "is" is.
To a Spanish speaker, the following are two different facts:
"Juan es loco."
"Juan está loco."
I apologize for using Spanish rather than a more common language. Spanish
is the only language, other than English, that I know well enough to use to
illustrate the point.
I recall that Bob Badour attributed to Dijkstra the motto that one should
always do computer science in a second language.