Re: Another view on analysis and ER

From: mAsterdam <mAsterdam_at_vrijdag.org>
Date: Fri, 07 Dec 2007 17:26:51 +0100
Message-ID: <47597326$0$227$e4fe514c_at_news.xs4all.nl>


David Cressey schreef:
> mAsterdam wrote

>> Sorry for butting in this late, and not even completely on topic.
>> 'Facts' triggered my interest.
>>
>> Jon Heggland wrote:
>>
>>> ...(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.

Did Clinton's argument hold up? Oh wait :-)

Under which interpretation/condition of "is" would "John is in Canada" not need a time to be of interest?

> In Spanish, "John is 33 years old" will be expressed roughly like this:
> "John has 33 years."
> The verb "to be" is not used.
>
> "John is a man" will be expressed using one of the Spanish verbs "to be".
>
> "John is in Canada" will be expressed using the other of the Spanish verbs
> "to be".
>
> This distinction is wasted on a person who thinks about the facts in
> English. But it isn't wasted, at all, on a person who thinks about the
> facts in Spanish. There are even statements in Spanish that differ only by
> which verb is used.

For the facttype of which "John is 33" is a statement it is possible to make language-specific intension, and a language neutral extension:

[English]: <Person> is <Age> years old
[Nederlands]: <Persoon> is <Leeftijd> jaar oud



John, 33

> To a Spanish speaker, the following are two different facts:
> "Juan es loco."
> "Juan está loco."

What do they mean? My Spanish sucks.

> Does this mean that the content of the database is different, depending on
> the first language of the observer?

One requirement for a database can be:
make sure that the content is language-neutral.

> 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.

Quoting Dijkstra can make anyone look sensible. Received on Fri Dec 07 2007 - 17:26:51 CET

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