Re: Representing Student Activity Score

> > > > Could you show how to explicity represent the following info in RM:
> > > > john take test.
> > > > john get 95.
> > > > (john get 95) for (john take test).
> > >
> > > PERSON SCORE
> > > John 50
> > > Mary 75
> >
> > A program could derive each tuple's relationship to a person and score
> > (ie tuple1's person is john, tuple1's score is 50. It doesn't encode
> > the original info explicitly.

> 
> Because it is not necessary (or proper) to refer to the tuple by its (row)
> number. Sets are not ordered, so tuple numbers are meaningless. 
> They can change. 

The expression "tuple1" is a short method of identifying one of the two tuples as listed above instead of saying "the tuple whose attribute person has the value john and whose attribute score has the value 50". The expression "tuple1" is not meant to imply its position among tuples in the db or that its position couldn't change.

By the way, your response to "[above table] doesn't encode the original info explicitly" being "Because it is not necessary (or proper) to refer to the tuple by its number" is illogical as the short method of referring to tuple by its position as listed above does not counter that the above table doesn't enode the original info explicitly.

> Besides, why refer to a tuple by its number rather than by the Primary Key?

Because no one has defined a primary key on the relation and neither is it a requirement. The "1" in "tuple1" is meant to identify tuple's position as listed above, not its ID or its position in the db.

> > > SELECT person||' scored '||score||' in the exam.' FROM =test_scores;
> > > John scored 50 in the exam.
> > > Mary scored 75 in the exam.
> >
> > SQL statement is providing relationship between the data, not data in db

> 
> Ummm, dude, somewhere along the line, some bit of code is going to provide
> the relationship, unless you've invented a psychic computer interface.

Why would you want to encode the relationship between things in code (or SQL statements) when it can be done with data in the db, as does XDb2/TM, as shown at www.xdb2.com/Example/StudentActivityScore.asp ?

> the programmer must know all possible questions that will be asked, > and all possible relationships among the data- all before entering any data.

A long-term goal of mine is for the "programmer" to be computer/software and for it to know relationships among the data, the relationships should be entered into the db.

> .. system works well with known sample data under controlled conditions.

A long-term goal of mine is for a system to work well with unknown data under uncontrolled conditions, somewhat like a human being.

> I suspect you have an interest in AI, and it looks like you are trying to > connect an inference engine to an rdb, but you tripped over the db theory.

XDb2/TM stores the following things explicitly including relationships, in a NULL-less and normalized manner. Could you untrip me and show how to represent the following explicitly using RM theory?

 john take test.
 john get 95.
 (john get 95) for (john take test). Received on Fri Jul 23 2004 - 20:54:44 CEST