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Re: terminology

From: Cimode <cimode_at_hotmail.com>
Date: 18 Jun 2006 11:55:56 -0700
Message-ID: <1150656956.737834.16790@g10g2000cwb.googlegroups.com>


Speaking of terminilogy...and preciseness...

Marshall wrote:
> There's a lot of terminological discussion floating around right now,
> and some of it is really bad.
>
> Most basically, a relation is a subset of a product of sets.
What the hell is a product of sets? sets of what? product is exclusively an arithmetic operation. Which one are refering to?

What allows to qualify a relation as a subset of the exclusive output arithmetics operations?

> In the c.d.t. context, we mean a little more than that, because
> of keys and possibly constraints, and because each of the sets
> has an associated name, but that's the basic idea. A particular
> relation is a value.

No. A particular occurence of relvar in time is a value. A relation is not a relvar. A relvar is an elementary component of a relation.

> A variable is a construct that has an associated value, and also
A variable is defined and can live totally independently from the values it holds...Defining a value holder according to a value is incorrect.

As an analogy, do you define a recipient according to its content? Do you define a glass of water according to water...Both are totally independent. Water is H2O and glass of water is mainly Carbon

> has some associated destructive update operation, usually
> assignment.

What the hell is associated *destructive update operation*? A sci fi movie?

In statically typed languages, a variable has an
> associated type, and updates to the variable must conform
> to that type, possibly taking subtyping in to account.
So basically you state a variable has type, a value has type, a relation has type?
The three are different. How do you define update? Subtypes are a totally different subjects....You mix up everything!

> "Relvar" is simply an abbrevation for "relation variable." No
> more and no less--just shorthand. It is a variable, and the
> static type of the variable is a relation type.
I totally disagree with such definition because your premise is false you assume
relation = relvar = relvalue

>
> Note that there is no distinction between "relation" and "relation
> value" the same way there is no distinction between "integer"
> and "integer value."

No. a relation is a particular of function a *relation value* is a value drawn from a domain (RM) or ensemble of values. I will use your analogy of integers to prove you wrong. *integer* refers to the complete set of values drawn from the ensemble of integers meaning ALL of them. An integer value is one specific occuring value...Which basically makes say that

ALL integers = one integer...

>There are values and there are variables.
What a level of incoherence

You just stated above that there is no difference between a variable and a value...Now you state the difference between...Make up you mind!!!

> Values have a type, and in most systems variables have
> a type, such that the variable and its associated value are
> guaranteed to have compatible types, either because the
> types are equal or because the value's type is a subtype of
> the variable's type.

You make so many confusions about RM, I seriously believe you get back to reading about RM.

> Marshall
Received on Sun Jun 18 2006 - 13:55:56 CDT

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