Re: Constraints and Functional Dependencies

From: Tony D <>
Date: 27 Feb 2007 15:20:09 -0800
Message-ID: <>

[Quoted] On Feb 27, 6:29 pm, "Marshall" <> wrote:
> Do you have any references for QUEL for someone who would like
> to read about the language?

Well, you can go to and download a GPL edition of Ingres 2006 and the documentation, and read about QUEL and even try it out ;) Sadly, QUEL is in something approaching deep freeze, as Ingres don't add QUEL specifics for new things they add to the SQL implementation, but it's pretty much industrial strength - to the point that many of Ingres' system catalogues are QUEL views.

> If one is interested in learning about
> functional languages, or OO languages, one has many to choose
> from, and can see many different approaches being tried, and
> compare features, etc. For relational languages, there is SQL,
> and not a lot else.

I was going to bemoan this in my first post, but opted not to. Has anyone ever made publicly available an implementation of the likes of Modula-R, I wonder ?

> Setl or Nestl? Not altogether algebraic. There's TutD, of course. I
> am impressed with its semantics, but I can't say I find it compelling.

I wish I could agree about the semantics, but I'm not yet convinced. I'm also not 100% convinced about the utility of possreps. What exactly do they get me that conversion functions don't, with fewer additional concepts ? The utility I *do* see for them is in version control. Imagine you have a database with user defined types, and you need to add some additional detail to one of those types. Without possreps, you may end up having to copy the data out, amend the datatype definition, then copy the data back in. Hardly a vote grabber. (That's (a) well off the topic and (b) overly practical, I know...)

> Its relational features are
> of course very advanced but outside of that it's quite staid.
> My aspiration is for the advanced relational semantics of
> TutD combined with some of the goodness of modern
> functional languages.

> My expectation, Tony, is that you
> would be sympathetic for the desire for higher order
> functions. :-)

Now whatever gave you *that* idea, Marshall ? ;))))

Haskell + full support for relations = a very worthwhile experiment,to me.

> In any event, I expect I would enjoy reading about QUEL.

I think you would. Go for it :) Any questions, ask Roy Hann - he did have an email alias of "quelgeek" at one time, I'm pretty sure !

  • Tony
Received on Wed Feb 28 2007 - 00:20:09 CET

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