Re: BCNF and relational algebra
Date: Tue, 24 Feb 2004 00:12:44 +0100
Message-ID: <403a88ed$0$568$e4fe514c_at_news.xs4all.nl>
Perception wrote:
> "mAsterdam" <mAsterdam_at_vrijdag.org> wrote in message>>>B:Date
>>>...
>>>A:Patient Identifier -> Patient Name, Ward
>>>C:Doctor -> Clinic
>>
>>Start with providing the predicates which
>>would let the population data convey true propositions.
> > > Could you please elaborate on what you mean by true propositions?
Well, you are supposed to be the domain expert.
Domain in both the broad sense of 'universe of discourse', what are we talking about, what kind of facts should the content of these rows reflect, and in a more detailed sense: what is the valid set of values for each attribute/column/field/item/property/whathaveyou (a.k.a. it's type).
> >
>>Example:
>>A:
>> A:Patient Identifier -> Patient Name, Ward
>> ------------------ ------------ ----
>> 1 Johnson IC
>> 2 Perception RE
>>
>>What do these rows *mean* ?
>>That should give a clue to the predicate for A.
I can only take a wild guess from this.
You should be able to make a more meaningful set, but you could take
this to start with.
A first try could be:
[Attributes]
Patient Identifer: type=integer.
It comes into existence when <some meaningful event in the universe of
discourse> (up to you)
Patient Name: type=text.
Given name, manually copied from his id-card when hen the patient is
admitted to a ward (... just fantasizing to give you an idea, ehrrrm
elaborate)
Ward: type=two characters
The code at the entrance door of the ward.
[Predicate]
A possible predicate could be:
A Patient, identified by "Patient Identifier", with the given name "Patient Name", has been released from our Ward "Ward" on last tuesday.
(still improvising, that much should be clear)
[Propositions]
The propositions would now become:
Patient 1, Johnson was released from the IC Ward on tuesday. Patient 2, Perception was released from the RE Ward on tuesday.
Now you may not like the 'on tuesday' part (or other parts). I added it to illustrate that *if* this would be the predicate, this would be the set of propositons conveyed by the population. It might be a nice list for the billing department (they would need mor, of course).
In short: what does it *mean*.
HTH Received on Tue Feb 24 2004 - 00:12:44 CET