A different definition of MINUS, Part 1

#11

Brian Selzer wrote:

Quote:

Just some food for thought:

1. The scope that McGoveran referred to is the set of all tuples that appear
in any possible value for the relvar.
...

I's rather say he was talking about the scope of a complement, a
standpoint that seems more useful to me.

Quote:

2. When dealing with an update, there is always a before and an after,
unless the update is null. If "Paul is asleep," and the update states,
"Paul is awake," then which is the case? Is he asleep or is he awake? He
can't be both. An expression of the algebra can only deal with one set of
circumstances--not both, since the algebra is for determining what is the
case rather than asserting what is the case. Each possible value for a
database corresponds to a distinct logical proposition, yet only one of
those propositions represents what /is/ the case. So whenever there is an
update (unless it is null, of course), you are always dealing with two
distinct propositions representing /what has been the case/ and /what is now
the case/. I just think that ignoring before and after invites dire
consequences.

You are really talking about language implementation and its various
psychological aspects, introducing all kinds of notions I don't think
are important to the logical question of equations that represent the
differences between certain relations. I'm only talking about the
A-algebra's logical implications in the RM. You may want me to talk
about language but I won't, at least, not much.

#12

Brian Selzer wrote:

Quote:

Just some food for thought:

1. The scope that McGoveran referred to is the set of all tuples that appear
in any possible value for the relvar.
...

I's rather say he was talking about the scope of a complement, a
standpoint that seems more useful to me.

Quote:

2. When dealing with an update, there is always a before and an after,
unless the update is null. If "Paul is asleep," and the update states,
"Paul is awake," then which is the case? Is he asleep or is he awake? He
can't be both. An expression of the algebra can only deal with one set of
circumstances--not both, since the algebra is for determining what is the
case rather than asserting what is the case. Each possible value for a
database corresponds to a distinct logical proposition, yet only one of
those propositions represents what /is/ the case. So whenever there is an
update (unless it is null, of course), you are always dealing with two
distinct propositions representing /what has been the case/ and /what is now
the case/. I just think that ignoring before and after invites dire
consequences.

You are really talking about language implementation and its various
psychological aspects, introducing all kinds of notions I don't think
are important to the logical question of equations that represent the
differences between certain relations. I'm only talking about the
A-algebra's logical implications in the RM. You may want me to talk
about language but I won't, at least, not much.

#13

Brian Selzer wrote:

Quote:

Just some food for thought:

1. The scope that McGoveran referred to is the set of all tuples that appear
in any possible value for the relvar.
...

I's rather say he was talking about the scope of a complement, a
standpoint that seems more useful to me.

Quote:

2. When dealing with an update, there is always a before and an after,
unless the update is null. If "Paul is asleep," and the update states,
"Paul is awake," then which is the case? Is he asleep or is he awake? He
can't be both. An expression of the algebra can only deal with one set of
circumstances--not both, since the algebra is for determining what is the
case rather than asserting what is the case. Each possible value for a
database corresponds to a distinct logical proposition, yet only one of
those propositions represents what /is/ the case. So whenever there is an
update (unless it is null, of course), you are always dealing with two
distinct propositions representing /what has been the case/ and /what is now
the case/. I just think that ignoring before and after invites dire
consequences.

You are really talking about language implementation and its various
psychological aspects, introducing all kinds of notions I don't think
are important to the logical question of equations that represent the
differences between certain relations. I'm only talking about the
A-algebra's logical implications in the RM. You may want me to talk
about language but I won't, at least, not much.

#14

Brian Selzer wrote:

Quote:

Just some food for thought:

1. The scope that McGoveran referred to is the set of all tuples that appear
in any possible value for the relvar.
...

I's rather say he was talking about the scope of a complement, a
standpoint that seems more useful to me.

Quote:

2. When dealing with an update, there is always a before and an after,
unless the update is null. If "Paul is asleep," and the update states,
"Paul is awake," then which is the case? Is he asleep or is he awake? He
can't be both. An expression of the algebra can only deal with one set of
circumstances--not both, since the algebra is for determining what is the
case rather than asserting what is the case. Each possible value for a
database corresponds to a distinct logical proposition, yet only one of
those propositions represents what /is/ the case. So whenever there is an
update (unless it is null, of course), you are always dealing with two
distinct propositions representing /what has been the case/ and /what is now
the case/. I just think that ignoring before and after invites dire
consequences.

You are really talking about language implementation and its various
psychological aspects, introducing all kinds of notions I don't think
are important to the logical question of equations that represent the
differences between certain relations. I'm only talking about the
A-algebra's logical implications in the RM. You may want me to talk
about language but I won't, at least, not much.

#15

Brian Selzer wrote:

Quote:

Just some food for thought:

1. The scope that McGoveran referred to is the set of all tuples that appear
in any possible value for the relvar.
...

I's rather say he was talking about the scope of a complement, a
standpoint that seems more useful to me.

Quote:

2. When dealing with an update, there is always a before and an after,
unless the update is null. If "Paul is asleep," and the update states,
"Paul is awake," then which is the case? Is he asleep or is he awake? He
can't be both. An expression of the algebra can only deal with one set of
circumstances--not both, since the algebra is for determining what is the
case rather than asserting what is the case. Each possible value for a
database corresponds to a distinct logical proposition, yet only one of
those propositions represents what /is/ the case. So whenever there is an
update (unless it is null, of course), you are always dealing with two
distinct propositions representing /what has been the case/ and /what is now
the case/. I just think that ignoring before and after invites dire
consequences.

You are really talking about language implementation and its various
psychological aspects, introducing all kinds of notions I don't think
are important to the logical question of equations that represent the
differences between certain relations. I'm only talking about the
A-algebra's logical implications in the RM. You may want me to talk
about language but I won't, at least, not much.

#16

Brian Selzer wrote:

Quote:

Just some food for thought:

1. The scope that McGoveran referred to is the set of all tuples that appear
in any possible value for the relvar.
...

I's rather say he was talking about the scope of a complement, a
standpoint that seems more useful to me.

Quote:

2. When dealing with an update, there is always a before and an after,
unless the update is null. If "Paul is asleep," and the update states,
"Paul is awake," then which is the case? Is he asleep or is he awake? He
can't be both. An expression of the algebra can only deal with one set of
circumstances--not both, since the algebra is for determining what is the
case rather than asserting what is the case. Each possible value for a
database corresponds to a distinct logical proposition, yet only one of
those propositions represents what /is/ the case. So whenever there is an
update (unless it is null, of course), you are always dealing with two
distinct propositions representing /what has been the case/ and /what is now
the case/. I just think that ignoring before and after invites dire
consequences.

You are really talking about language implementation and its various
psychological aspects, introducing all kinds of notions I don't think
are important to the logical question of equations that represent the
differences between certain relations. I'm only talking about the
A-algebra's logical implications in the RM. You may want me to talk
about language but I won't, at least, not much.

#17

Brian Selzer wrote:

Quote:

Just some food for thought:

1. The scope that McGoveran referred to is the set of all tuples that appear
in any possible value for the relvar.
...

I's rather say he was talking about the scope of a complement, a
standpoint that seems more useful to me.

Quote:

2. When dealing with an update, there is always a before and an after,
unless the update is null. If "Paul is asleep," and the update states,
"Paul is awake," then which is the case? Is he asleep or is he awake? He
can't be both. An expression of the algebra can only deal with one set of
circumstances--not both, since the algebra is for determining what is the
case rather than asserting what is the case. Each possible value for a
database corresponds to a distinct logical proposition, yet only one of
those propositions represents what /is/ the case. So whenever there is an
update (unless it is null, of course), you are always dealing with two
distinct propositions representing /what has been the case/ and /what is now
the case/. I just think that ignoring before and after invites dire
consequences.

You are really talking about language implementation and its various
psychological aspects, introducing all kinds of notions I don't think
are important to the logical question of equations that represent the
differences between certain relations. I'm only talking about the
A-algebra's logical implications in the RM. You may want me to talk
about language but I won't, at least, not much.

#18

Brian Selzer wrote:

Quote:

Just some food for thought:

1. The scope that McGoveran referred to is the set of all tuples that appear
in any possible value for the relvar.
...

I's rather say he was talking about the scope of a complement, a
standpoint that seems more useful to me.

Quote:

2. When dealing with an update, there is always a before and an after,
unless the update is null. If "Paul is asleep," and the update states,
"Paul is awake," then which is the case? Is he asleep or is he awake? He
can't be both. An expression of the algebra can only deal with one set of
circumstances--not both, since the algebra is for determining what is the
case rather than asserting what is the case. Each possible value for a
database corresponds to a distinct logical proposition, yet only one of
those propositions represents what /is/ the case. So whenever there is an
update (unless it is null, of course), you are always dealing with two
distinct propositions representing /what has been the case/ and /what is now
the case/. I just think that ignoring before and after invites dire
consequences.

You are really talking about language implementation and its various
psychological aspects, introducing all kinds of notions I don't think
are important to the logical question of equations that represent the
differences between certain relations. I'm only talking about the
A-algebra's logical implications in the RM. You may want me to talk
about language but I won't, at least, not much.

#19

Brian Selzer wrote:

Quote:

Just some food for thought:

1. The scope that McGoveran referred to is the set of all tuples that appear
in any possible value for the relvar.
...

I's rather say he was talking about the scope of a complement, a
standpoint that seems more useful to me.

Quote:

2. When dealing with an update, there is always a before and an after,
unless the update is null. If "Paul is asleep," and the update states,
"Paul is awake," then which is the case? Is he asleep or is he awake? He
can't be both. An expression of the algebra can only deal with one set of
circumstances--not both, since the algebra is for determining what is the
case rather than asserting what is the case. Each possible value for a
database corresponds to a distinct logical proposition, yet only one of
those propositions represents what /is/ the case. So whenever there is an
update (unless it is null, of course), you are always dealing with two
distinct propositions representing /what has been the case/ and /what is now
the case/. I just think that ignoring before and after invites dire
consequences.

You are really talking about language implementation and its various
psychological aspects, introducing all kinds of notions I don't think
are important to the logical question of equations that represent the
differences between certain relations. I'm only talking about the
A-algebra's logical implications in the RM. You may want me to talk
about language but I won't, at least, not much.

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A different definition of MINUS, Part 1

comp.databases.theory comp.databases.theory

Re: A different definition of MINUS, Part 1 - 12-17-2008 , 08:23 AM

Re: A different definition of MINUS, Part 1 - 12-17-2008 , 08:23 AM

Re: A different definition of MINUS, Part 1 - 12-17-2008 , 08:23 AM

Re: A different definition of MINUS, Part 1 - 12-17-2008 , 08:23 AM

Re: A different definition of MINUS, Part 1 - 12-17-2008 , 08:23 AM

Re: A different definition of MINUS, Part 1 - 12-17-2008 , 08:23 AM

Re: A different definition of MINUS, Part 1 - 12-17-2008 , 08:23 AM

Re: A different definition of MINUS, Part 1 - 12-17-2008 , 08:23 AM

Re: A different definition of MINUS, Part 1 - 12-17-2008 , 08:23 AM