Re: XQuery (and XML) vs LISP

"Marshall Spight" <marshall.spight_at_gmail.com> wrote:

>Mark Johnson wrote:
>> Christopher Browne <cbbrowne_at_acm.org> wrote:

>> The thing that has bothered me is that those promoting the relational
>> model typically provide worthless examples, typically employee and
>> department, and seem to almost religiously avoid non-trivial working
>> examples, particularly those that might seem problematic for the
>> scheme.

>Employees and departments are tables that will exist in a
>(probably relational) database in the HR department of
>every corporation in the world. It is about as real-world
>an example as you can get. It may be the case that
>you don't write applications that do that sort of thing,
>but lots of people do.

No they don't. Such examples that are shown are trivial. You don't pay someone to do something that easy, that simple. A real world requirement isn't anything like that. The other guy, in fact, agreed with me, but defended the practice. So you disagree with him, as well.

And I still think that you particularly don't see certain examples because they might seem to be counter-examples of entire scheme.

>If one belongs to the crowd that says, "I want a J2EE book, and
>the more it weighs the better it must be," one probably does
>not appreciate this perspective.

And I'm sure it rains on Mondays in Sweden, depending. Which has what to do with what?

> > For example, what is a type? What goes in the 'set', as you express
>> it, never mind any particular domain? Why is a book a 'type', when
>> there are various sorts of books? Why is a chapter a 'type', when the
>> chapters in the same book might be of a very different sort? Is the
>> appendix which is more an index a type to itself? And so on. Are the
>> paragraphs a 'type', and is the paragraph in chapter 4 different than
>> the paragraph entities in relation chapter 5?

>I don't understand your point here. It seems to be written to
>critique a set of types to describe a book. What types and
>what book? Or are you saying that type theory has nothing
>useful to say about books?

I'm just wondering what it says about them, given that was the example.

>> To normalize things does
>> it require literally hundreds and hundreds of 'relations'/tables to
>> represent the structure?

>How many classes does a Java program have? How many
>people does a company need?

Do you disagree with that idea that a more normalized scheme tends to increase the number of tables? I don't know the formula? But are you saying such a formula could not even exist?

>> Just think of the 'joins'.

>Joins are wonderful;

Most anything to excess ceases to be wonderful, unless we're literally talking the beatific vision (which isn't something you or I could live through, by the way).

>> And wasn't the RM
>> intended to free people from the 'tyranny of structure'?

>No.
>And anyway, you can't not have structure.

No, of course not. Structure. It's transcendent. It transcends any scheme. Any scheme has to represent that structure, that order. Obviously. Or else it's representing something else.

But wasn't the idea to separate out any fixed structure by reducing a very well-defined scheme to a series of connected relations? Wasn't the idea that while, again obviously, the RM itself describes a fairly rigid structure, it didn't face the problems of an early generation of COBOL, for example?

If I misunderstand, then so be it. If that wasn't a typical problem, then what did Codd set out to ameliorate? Received on Sat Feb 18 2006 - 01:06:47 CET