Hi again :-)
2013/4/9 François Lacombe <francois.laco...@telecom-bretagne.eu>
> This is where I still don't understand you: why do I need to specify that
>> a feature XXX has the role XXX? Why do I need to specify, that a generator
>> is a generator? A substation a substation? A dam a dam? A valve a valve? A
>> weir a weir? And so on.
>>
>
> This is just because a role must be specified.
>
Why do I have to specify a role?
> When all features must be member of power=plant relation (because of lack
> of perimeter), what role can I associate to a generator except... generator?
>
None at all. Because if a generator is a member of a plant, its role is
generator. So no need to specify it. Even more: if you force roles to be
specified, someone comes along and specifies a generator as dam. This is of
course can be very easily and automatically detected as all generators must
be generators. But wait! If it can be automatically detected, why should it
be specified?
Imagine a basket ("relation") full of fruits ("members"). Everyone knows
the fruits and their names("tags"). Now someone puts notes ("roles") on the
fruits. On all apples now is a note saying "apple", on all pears it says
"pear", and so on. Would you think of those notes as helpful in any way?
You are a professional fruit merchant ("mapper"). Now your government ("the
one which writes the proposal" ;-) ) decides that in order to sell your
fruits you have to put one of those notes on each of them. The neighbours
boy comes along and switches all the notes. What do you think of the notes?
Are they worth the effort or would you consider changing your job (to
"google map maker")?
(Obviously I like illustrative comparisons)
Best regards!
Martin
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