Re: Clues on modeling a really simple concept

On 7 abr, 02:43, Bob Badour <bbad..._at_pei.sympatico.ca> wrote:
> Spike wrote:
> > On 7 abr, 01:38, jefftyzzer <jefftyz..._at_sbcglobal.net> wrote:
>
> >>On Apr 6, 3:40 pm, Spike <fau..._at_gmail.com> wrote:
>
> >>>On 6 abr, 23:11, Bernard Peek <b..._at_shrdlu.com> wrote:
>
> >>>>In message
> >>>><16d72645-6a6b-4fd4-bccf-d5002970f..._at_q2g2000vbr.googlegroups.com>,
> >>>>Spike <fau..._at_gmail.com> writes
>
> >>>>>My question is: Should i add a relationship between galleries and
> >>>>>users?
>
> >>>>>I would like to query which galleries a user has, and i don't really
> >>>>>know if it is worth adding a foreign key rather than doing a three-
> >>>>>level join query each time i want to obtain this data.
>
> >>>>Less is more. The database is fully normalised without adding an extra
> >>>>relationship. You shouldn't denormalise without a good reason.
> >>>>Denormalised systems are usually more fragile and will cost you more
> >>>>time in programming and maintenance.
>
> >>>>Of course if there is some other real-world relationship between
> >>>>galleries and users you may need to change the model. Do galleries have
> >>>>Owners, for instance and would those be Users?
>
> >>>>--
> >>>>Bernard Peek
>
> >>>Hi!
>
> >>>I was thinking about system performance vs. normalization. By adding
> >>>that extra relationship, three-level joins can be avoided, and so
> >>>stressing the dbms too much.
>
> >>>Do you think is a good idea in general to denormalize the data model
> >>>by means of performance?
>
> >>>Thanks!
>
> >>Spike,
>
> >>I'm not sure if you're deliberately trying to be provocative, but I'd
> >>say it's fair to characterize this newsgroup as denormalization-
> >>hostile ;-).
>
> > Its the very first time i post (and even read) this newsgroup, so no,
> > im not deliberately provocative.
>
> >>What's more important, I think, is to put first things first, and as I
> >>hinted at--and others made explicit--what's paramount is getting the
> >>requirements right and accurately modeling the problem domain. If
> >>users create galleries, and/or galleries can exist independently of
> >>any pictures being assigned to them, then model accordingly. Period.
>
> >>Bottom-line, IMHO: 1) model the domain accurately, and 2) deviate from
> >>the model only when *truly* warranted (NB that often denormalization
> >>is zero-sum--who cares when the data comes back faster when it's wrong
> >>or contradictory?). You might want to see if you can find a copy of
> >>"The Normal Is So... Interesting" by Chris Date (DBP&D 11/97) for more
> >>on the topic of denormalization. Many other sources abound.
>
> > The problem here is that users should be able to upload pictures
> > without specifying a particular gallery (i will use a default one).
> > In a similar way, the should be able to create an empty gallery.
>
> > Thus, there are two options: make a relationship between users and
> > galleries or create a record in the join table between pictures and
> > galleries with null values on foreign keys.
>
> The latter is wrong. Wrong in so many ways and on so many levels, it
> would be tedious to try to enumerate them.
>
> If a user can create and own empty galleries, then, obviously, gallery
> has some direct join path to user. Failure to capture that would lead to
> stupid errors like the inclusion of another person's picture in one's
> gallery suddenly conferring ownership of the gallery to the other
> person. That, in itself, is an obvious potential security flaw.
>
> I strongly recommend you learn at least some of the fundamentals before
> you start designing anything that might impact the public.
>
> > I dont really like any of the two options, but if one of them
> > increases overall performance, that will be a good decision maker.
>
> Like and dislike has nothing to do with acting like a professional.
> While performance is an important consideration, fast and incorrect is
> no better than slow and incorrect; it is simply incorrect.
>
> A responsible and competent designer starts with correct and works from
> there to achieve the required performance characteristics. Only an
> ignorant boob would design for performance without any consideration for
> the actual requirements.

I think (and hope) i have not expressed myself correctly.

Im modeling this software for fun. It is a private project. No requirements to relax and no security issues because it is just a draft, an idea.

I just wanted some clues on this kind of things. As simple as "This is what i would do: ...".

It turns out that this has become something like an aggressive modeling lesson, that i may or may not need (im a software engineer, btw), and simply thats not the point.

Provided this wold had been a "real life" project, i would be cautious and respect normal models based on what someone asks for as i use to.

So please, stop that tad dismissive tone. It leads to nothing constructive.

Regards. Received on Wed Apr 08 2009 - 03:15:01 CEST