[Tagging] Power generation refinement: power plant model evolution

Martin Vonwald (imagic) imagic.osm at gmail.com
Tue Apr 9 16:21:07 UTC 2013


Hi!

Am 09.04.2013 um 17:22 schrieb François Lacombe <francois.lacombe at telecom-bretagne.eu>:

> In my mind, define a role in a relation is mandatory but you say it's definitely not right.

Roles can make sense. For example ways in a route relation may have the role forward or backward, if this specific way is only used in one direction. This is a property of the route and not of the way, therefore it is tagged as role in the relation.

A generator is different. It simply is a generator and its role within the plant is to be a generator. So there is no need to explicitly specify it.
Furthermore think of the consumers. Example: the process one feature of the plant. If the plant is described by a relation the consumers have two sources about the type of that feature: the tags on the feature and the relation. As the relation is not always present they will trust the tags on the feature and ignore the role in the relation. 


> I agree to say generator / substation and other roles are not relevant and maybe redundant but they formalize association between features and power plant, which features' tags (or plants' tags) won't do ever since they're attached to objects, not to the link between objects.

Which association would they formalise? If a generator is part of a plant its function (aka role) is to work as generator. The association is created by adding the generator to the plant.


> To make proposal lighter I would consent to remove generator, substation roles and most of the specific roles from non-enclosed power plants relations (perimeter has already left the proposal as you maybe noticed).

I'm just curious about the perimeter: what would we do if a plant has multiple perimeters? How would we map them? 


> But that will allow mappers to use any values they want to use, not convince them into letting the "role" field blank.

Does it matter? Besides some special roles defined by the proposal, what would a consumer do with an unknown role?


Best regards,
Martin


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