Re: Storing data and code in a Db with LISP-like interface
Date: Wed, 19 Apr 2006 10:17:22 +0300
"Nick Malik [Microsoft]" <nickmalik_at_hotmail.nospam.com> wrote in message
> "Neo" <neo55592_at_hotmail.com> wrote in message
> >> ... calling one of us an idiot. Not sure who. :-)
> > Well if you don't want the compliment, I'll take it :)
> >> Prolog is not an inherently type-safe language ...
> > This is slightly off-topic, but I am curious about your view:
> These are good questions, but I'm not sure if you are asking me about my
> views on relational data management or on logical rules management. The
> difference is simple. Relational describes relationships like 'is a' and
> 'has a' and 'is defined by' while logical rules management simply states
> 'the relationship is what you define it to be'.
> It has been well over a decade since I wrote Prolog code, so if someone
> reading this newsgroup knows Prolog and they see this, my sincere
> The concept is what I'm trying to convey.
Your Prolog is fine. I also wrote Prolog code 10 years ago (from 1991).
> > 1) What is the proper name of the relationship between person and John,
> > person and Mary, fruit and apple, fruit and banana, etc. Ie, fill the
> > verb in: person ____ john.
> > 2) What is the proper name of the reverse relationship between John and
> > person, Mary and person, apple and fruit, banana and fruit, etc. Ie,
> > fill the verb in: john ___ person.
> (to which the system responds)
> A = person
> (I skipped your question. The answer to the logic of your question is: I
> would consider john to be a named instance of the noun 'person').
> > 3) Just as John and Mary "are" persons, and apple and banana "are"
> > fruits, what are person and fruit?
> person is a noun. fruit is a noun. In Prolog, they are atoms. They have
> no 'meaning' except as defined by their relationship with john and banana.
> (You will notice that I use lower case, even for proper names. In Prolog,
> lower case tokens are 'atoms' while a token that begins with a capital
> letter is a variable).
> > 4) Supposing the answer to question 3 is xyz, what is the proper name
> > of the relationship between xyz and person, xyz and fruit, etc?
> not a sensible question in Prolog context. There is no notion of subtype
> supertype. Only expression. Imagine that we are talking about Boolean
> logic. A or B. Is A a variable? If we say "A is a B and B is a C,
> therefore A is a C," we have defined the transitive property of 'is a'.
> Before making the statement, the verb 'is a' had no such property. The
> scope of this property may be quite limited. Prolog assumes this. Most
> data management languages have a great many meta-rules. Prolog does too,
> but they are not based on the data. They are, instead, based on the
> > 5) Supposing the answer to question 3 is xyz, what is the proper name
> > of the reverse relationship between person and xyz, fruit and xyz, etc?
> See above.
> Let's say, in Prolog, you want to express the transitive nature of
> 'contains'. It could look like this:
> contains(A, B) :- contains(A, X), contains(X, B).
> Now let's establish some facts.
> contains(cup, coin).
> contains(bucket, cup).
> contains(box, bucket).
> contains(truck, box).
> contains(ship, truck).
> We are saying that the coin is in the cup is in the bucket is in the box
> in the truck is in the ship.
> Now, ask the question: is the coin in the truck?
> ? contains(truck, coin)
> to which the system responds:
> (or 'true.' Not sure anymore ;-).
> It does it by comparing the predicate contains/2 to each of the rules in
> system. There are six matching rules. One is an expression. The rest
> facts. The comparison doesn't match one of the facts, so the expression
> invoked. The expression says: any item is inside another item if you can
> find an intermediary where the item is in the intermediary and the
> intermediary is in the other item... RECURSIVE. Using a depth-first
> the system quickly finds that the coin is in a cup where a cup is in a
> bucket where a bucket is in a box where a box is in a truck, therefore the
> coin is in the truck.
Your post is fine.
Except Codd gone well beyond this with relations and databases. :-) Received on Wed Apr 19 2006 - 09:17:22 CEST