Re: c.d.theory glossary 0.0.1

From: Dawn M. Wolthuis <>
Date: Sun, 25 Apr 2004 10:18:58 -0500
Message-ID: <c6hb44$5rf$>

"mAsterdam" <> wrote in message news:408af3e3$0$575$
> Here is another start.
> If it is appreciated, I'll post the glossary once in a while.
sounds good. Thanks for doing this.
> --------------- "Some appetizer quote" - N.N.
> Glossary 0.0.1:
> april 25, 2004
> ---------------
> Preamble:
> ---------------
> This glossary seeks to limit lengthy misunderstandings in
> comp.database.theory.
> People tend to assume that words mean what they are
> accustomed to, and take for granted that the other
> posters have about the same connotations.
> They don't always.
> Some words are particularly suspect: database, object, normalisation.
> Some just cause minor annoyances, the misunderstanding is cleared and
> the discussion goes on: domain, type, transaction.
> We don't know well-accepted, formal or comprehensive definitions
> for everything. If you do have a useful reference, please provide it.
> If an informal description is all we have, so be it.
> Not:
> ---------------
A minor comment, but I had to look several times to see whether this was supposed to be Note: and I don't think that a title is required for this comment. If you need a title, then "This is Not" might be helpful to the reader.

> The glossary is not a dictionary or encyclopedia, such as FOLDOC,
> Wikipedia (, and the Web Dictionary of
> Cybernetics and Systems.
> Specific links to serve the glossary's purpose are welcome, of course.
> Also, it does not try to be a FAQ for "all things database".
> Credits:
> ---------------
> Contributions from within this group are not credited, quotes from
> elsewhere are. This is no ironclad rule. It is just that the first
> contributors like it that way.
> As a consequence, to all potential contributors:
> If you want your name stated please say so.
> Note to native english speakers:
> Please also check spelling and grammar mistaeks.
> ==============
> [Class]
> A class is what provides a name and a place for
> the abstract behavior of a set of objects
> said to belong to the class. (Larry Wall, Apocalypse 12)
I don't care for this definition, preferring that we have "A class is a " something. This is a weakly written definition, it seems to me. It doesn't look like it would help clear up Date's confusion on the term, for example. If we don't agree on what a class is, then several definitions would be better than something so vague, in my opinion. Is a class a software component?

> [Database]
> 1. Deluxe filesystem
> 2. Shared databank (E. Codd)
> [Entity]
> Thing of interest. (ISO)
> [Function]
> For now we have to live with *very different*
> meanings of _function_ when talking about databases:
> "The function of this function is to get the tuples from B
> that are functionally dependant on A." Please be specific.
> 1. A binary mathematical relation with at most
> one b for each a in (a,b).
> 2. A many-to-one relation of ordered pairs that
> maps each a to a unique b.

These two are identical, except in the words used, and I suspect we could pick one. I think the second is a little less easy to follow as you might be trying to figure out where the many-to-one is, especially since we are using that term to describe a single relation rather than a relationship between two relations. So, I'd pick the first and then add to it the next sentence:
> It is important to note that every function is, by definition, a relation.

> 3. purpose/use

"A purpose or use"

> 4. subroutine/procudure/method

"A subroutine, procedure, or method in software"

just a comment that, of course, 4 is the same def as 1, but indicates synonyms within the software world, thereby providing examples of the word "function" So, you might want to have two defs, the 1st with synonyms within s/w development and the 3rd, which is how the word is often used in English. Alternatively, putting the English use last might help, rather than splitting the more similar defs. I disagree that "function" is such a difficult word -- it is likely one of the easiest of these to get a def of.

5. I think this is 1 again, but it is worth stating that every "operator" is a function (where the domain for the function is a set of couples).

> [MultiValue, MV]
> 1. One name for the industry surrounding the Nelson-Pick data model.
> 2. A data field (or attribute) defined to permit a variable number of
> values as a list (array).
> [NULL] The insanity bit. No! The humility marker.
> mu: The absence of an answer to a question which requires an answer.
> /adj./
> 1. Attributes to something the absence of values.
> Ex: "The *null* set is the empty set, often represented by {}."
> /n. colloq./
> 1. A noted appearance of the absence of values.
> Ex: "This table contains *nulls*."
> Common usage:
> - Confusion arises when people use terms like "null value",
> a paradox to some, a contradictio in terminis to others.
> - Confusion arises due to the fact that nullness (the absence of value)
> is often represented on computers by the number 0.
> (Obviously, 0 is not null.)
> - In some contexts, 'null' and 'nil' mean the same thing; in others,
> they do not.
> In databases traditionally NULL is used and and opposed.
> If you want to go into this, please first search for
> mu NIL void NULL undef, 2VL 3VL.
> "It isn't the things we don't know that give us trouble.
> It's the things we know that ain't so." - Will Rogers
Fine for a start. Basically I would think we could come down to a 3VL & SQL usage (as "not a value") of NULL and a 2VL usage (as if it stood for "null set" which is a value). I do like the Will Rogers quote. I also miss your "Rows by any other name" quote at the top of the glossary, but I guess that is a matter of taste. If you keep the Will Rogers quote, then you might want to put your "Rows ..." statement back at the top.

> [Object]
> 1. Something intelligible or perceptible by the mind.
> 2. Model of an entity, characterised by behaviour and state. (ISO)

Neither of these hits the sweet spot, methinks. I'm guessing that often when we are talking about an object, it relates to something that can be stored in digital form. The first def let's us make the elephant an object, as well as the VHS tape. I'm sure there are times when we will use this term in this "English language" way. I would put that def last, however and start with ISO and then put something in that relates to what people are more likley to mean when they state "then store this object" or "persist the object" or "serialize the object" or "reference for the object".

> =============
> [[ToDo]]:
> Domain

I'll give it a weak start, just to help people jump in

  1. Given a relation R, a domain is a set Sn such that for each tuple (A1, A2, ...An, ...Am) in R, An is an element of Sn.

An issue we would have to address is that some consider domain = type (Date) while others consider one of these to include operators on the domain a

Another possible area of disagreement is whether the domain IS the set of all such values for this relation or is a superset from which these values could come

b. for any function f(a) = b the set from which valid values of a come is the domain of the function and the set of all values of b over the domain of the function is the range of the function (poorly stated -- but you get the idea and we can google for a def from mathematics to get better wording)

> Normalize (There are some notes by Dawn)
> Persistence
I think that we typically agree what this term means, but some people like to use it and some have their hair stand on end when it is used

> Relation

I'd suggest picking the original def from Codd in early papers and a more recent def that tosses in the heading, types, operators and the kitchen sink into the def of a relation.

> Type

See domain.

> Orthogonal

1. Perpendicular
something related to orthogonal concepts or orthogonal design or decomposition.

> Transaction

A set of database operations constituting a logical unit of work. Datatbase management software includes the ability to rollback complete transactions when an error is detected.

> Feel free to post suggestions to add or remove.
> [[Maybe Todo]]
> Necessary? Though obviously possible,
> I haven't seen misunderstandings,
> just strong opinions regarding these:
Agreed -- just leave 'em out for now

> Formal Theory
> =============
> Thank you for contributing.
> --
> Milestones? For the glossary I prefer inch-pebbles.
Received on Sun Apr 25 2004 - 17:18:58 CEST

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