Re: PIZZA time again :-)

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

> Although for the purposes of data modelling, I don't see
> that the order is relevant. The fact that the person who
> makes the pizza puts the toppings on in a certain order
> doesn't mean that order is relevant to how you specify
> a pizza. I've never heard anyone ordering pizza say
> anything like "please put the pepperoni down first,
> then the cheese." It's just "pepperoni and cheese" and
> its up to the person making the pizza to use the correct
> order.

I've already rested my case, so I'm not about to reenter the argument. But, since you're the "semantics guy" in this forum, I can't resist bringing up the question of semantics, implicit in the topic starter:

Here it is, all the way back to the beginning of the topic.

> Assume
> 1. there is a meaningful (or at least consequential)
> difference between:
>
> toppings([salami, mozarella, onions]).
> and
> toppings([mozarella, onions, salami]).

That word "meaningful" should be a clue that, ultimately, what we're discussing here is semantics.

The first question is, "meaningful in what context?" In terms of databases, there are at least two contexts: the context of the transaction that wrote the data, and the context of any transaction that reads the data. So the question is not "meaningful in use" but "meaningful in exchange".

The "obvious exchange" to me is the case where someone orders a Pizza from a delivery store (I just happened to use Domino's as an example), and orders a set of toppings. A while later, the delivery man shows up, the customer looks in the box, and says "this isn't what I ordered". The delivery man looks in the box, looks at the order, and says "yes, it is."

The customer grabs the order out of the delivery man's hand and looks at it and it says,

> toppings([mozarella, onions, salami]).

whereupon the customer says, "what I actually ordered was,
> toppings([salami, mozarella, onions])."

And the delivery man says, "well, it's the same thing.".

Now, I don't care whether the cook always adds the ingredients in a set order or not. All I care about are the context of the order and the context of the delivery.

So, to make a long story short, the question of "is it a list or a set"? boils down to "what are you going to do with the data"? This question is relevant to data modeling as well as to process modeling.

>
>
> Marshall
>
Received on Fri Sep 09 2005 - 21:08:22 CEST