Re: Ping: dawn, some mvl questions

dawn wrote:
> Not only that, but it is impossible to enumerate a set
> without the representation being a list.

Is this a confusion between logical and physical again? Regardless this also an example of begging the question or a circular argument.

> We write in lists, we speak in lists, and we are sometimes
> unaware of the meaning we give to a set when we list it.
> Does a grocery list refer to a set or would you lose
> something if you treated it that way?
>
> Retaining the order of something represented as a list
> might just provide ongoing information never verbalized.
> If a user lists something in an order, but we have defined
> it as a set because there has been no overt statement of
> the meaning of the order, might be losing information?
> Cheers! --dawn

If my grandmother hands me a recipe written on a piece of paper and I type it into emacs to store as a text file, do I lose information? What if some of the instructions were written heavily or traced over many times (ie bold) do I lose information if I use a plain text file? What if I sort the ingredients by quantity when she did alphabetically?

Of course no two physical representations (in the example text file versus paper) EVER retain exactly the same information since there is an vast amount of information held in any physical system (most of it unknown in fact) that is unique.

This is why it is so important to define logical (not physical!) models of data. Because we are free to define the logical model as we see fit and abstract away physical details that we deem insignificant. The word deem is key here. It is a choice. Our model is a choice. As long as we agree on the logical data model then we are fully capable of communicating information without loss.

Perhaps my grandmother assumed I would recognize the heavily traced ingredients as important and the others optional. Perhaps I just thought she was doodling. Regardless the flaw is not the logical data model it is her and my failure to AGREE on a COMMON data model. The flaw is in

> no overt statement of the meaning of the order

and

> information never verbalized

(though "verbalized" seems a poor choice of words perhaps for "modeled" or "represented"?)

If you want to use a logical data model that assumes some built-in implicit (physical?) order is meaningful nothing is stopping you. Though it is certainly not necessary to do so (the RM for example) and many have argued quite reasonably that such order dependence is a bad idea.

Next time I will have my grandmother handwrite her recipe in XML (blah! not! :)

• Keith ---