Where to set query item usage??

[ITEvilWoman]

We're using a 3 layer approach on our Framework models (database, modelling, presentation).
I've been looking over various 'best practice' documents and some say to set the item usage on the database layer and some say on the modelling layer but I can't find any information on why either of these options should be picked.
Is it personal preference or is are there any perfomance benifits to one rather than the other, or is there a development benifit to it????

Thanks in advance

Nat  ;D

[MFGF]

We're using a 3 layer approach on our Framework models (database, modelling, presentation).
I've been looking over various 'best practice' documents and some say to set the item usage on the database layer and some say on the modelling layer but I can't find any information on why either of these options should be picked.
Is it personal preference or is are there any perfomance benifits to one rather than the other, or is there a development benifit to it????

Thanks in advance

Nat  ;D

The way I see it is this:

DO IT IN THE DATABASE LAYER!!!!

Oops - did that come out a little shouty? Sorry - it's just that I feel a little strongly about it, having had to sort out all sorts of messes caused by other people who didn't, then got themselves very confused :)

My advice is to do it as part of the modelling of the database layer (bearing in mind that these objects are then used as the foundation for the higher layers). In doing things this way, when you create the higher modelling layer(s) above this, the usages in those layers will default to the usages in the database layer - even if you use the same item in three or four places.

Consider the alternative - not setting the usages in the database layer. This means that when you create anything new based on this layer, you have to check and potentially change the usages of every item in every query subject every time. Unless you forget. Or unless someone else gets involved and doesn't realise. Or unless someone inexperienced comes along and changes the database layer item usages after-the-fact, assuming that they will be inherited by items already created higher up in the model (which they won't). Or unless someone even more inexperienced comes along and sees that the usages in the model layer are different from those in the database layer and assumes that the database layer ones are definitively correct and so they change all the model ones to match.

You get my drift, I hope. In setting the usages in the database layer, you are making life easier for yourself and anyone else who works on the model later on. You are reducing the chance of inappropriate usages slipping through the net.

Of course, this is all just my own (humble) opinion - I have no grounds to say "this is the way you MUST do it". I would strongly recommend you consider my approach and the reasons why I take it, though.

Hope that helps!!

MF.

[ITEvilWoman]

MFGF, Thanks for the relpy.

Makes perfect sense to do it on the database layer for exaclty the reasons that you've mentioned!
Not that I've fallen foul of random Cognos 'Features' before but I did want to check that it wasn't going to cause a strange performance issue that I'd spend hours banging my head off my desk figuring out what the hey-ho was going on!

Beaker rules!

Nat  ;D