Re: Square pegs in round holes

From: Graham Bellamy <>
Date: Mon, 20 May 2002 06:25:01 +1000
Message-ID: <ac91i1$d94$>

"Mikito Harakiri" <> wrote in message

> Type Thickness(mm) Ratio(Sqm*mm/L) ContainerSize(L) TotalVolume(L)
> Cost($/L)
> Primer 1 0.99 20 40
> 0.50

I don't understand how your (Sqm*mm/L) is functioning. My Sq.m/L/mm is Square Meters per Litre for every 1mm thickness laid down.

> Having all data in uniform units has some added benefits. For example,
> you'll be able to query if all your materials fit into 14' truck.

In the entry form, would it be advisable to base it on a query that calculates the uniform value, eventhough it won't be showing it on that form, such that any future queries simply pluck that field out at will?

> > For convenience of standardising calculations, should I force the user to
> > enter Rate in a certain format (eg. L/Sq.m instead of Sq.m/L - user uses
> > both, depending on how it's written on the bottle). I've read it's not a
> > good idea to make the user conform for my benefit.
> There is neither L/Sq.m nor Sq.m/L in my proposed data model. 1 L/Sq.m
> = 1 mm and that's Thickness. Now, I'm not saying that the user
> necessarily have to be aware of that. Your application suggests to the
> end user entering either L/Sq.m, or Sq.m/L and then it translates it
> to canonical units and stores it.

I'm not sure what you mean by '1 L/Sq.m = 1 mm'. My model requires one field (thickness) to be mm, and another (Rate) to be [Sq.m/L or Sq.m/kg or Sq.m/L/mm or Sq.m/kg/mm]

> > Some treatments require a pigment to be added. The calculation of this is
> > dependent upon Qty of other materials, which again changes from product to
> > product. Examples of this:
> > Rate * (Total Qty of liquids [Primer + Resin + Sealers])
> > Rate * (Total Qty of Sealers only)
> > Rate * (Total Qty of Resin & Sealers [not Primer])
> Do you list pigment in the table of materials as well?

Well, I'm not sure how that would be done. I'd say not, because of the fact that eg. the Rate must be multiplied by the sum total of the quantity of all sealers). In this case the PigQty is not dependant on Rate and Area, but Rate and Mat'lQty. So I'm thinking it would have to be stored in another table.

> > Then somehow allow user to enter the rates in a form, and come up with some
> > code to figure out which materials to sum.
> In a treatment form a user adds marerials and rates for it. In your
> datamodel you have many-to-many relationship between Materials and
> Treatments. So what is the problem?

The fact that Pigment depends on other materials. Would you like to see a 56kb zip of the calcs I'm trying to transfer (small XL sheets)?

> > Though I'd be really screwed if eg. calc depended on all sealers except the
> > first.
...Still think I'd be screwed :)

If I haven't already mentioned it, I'm very thankful for your input.

Graham Received on Sun May 19 2002 - 22:25:01 CEST

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