[Tagging] Clarification on the role link in route relations

[stevea]

On Jan 10, 2022, at 11:19 PM, Peter Elderson <pelderson at gmail.com> wrote:
> stevea:
> I simply must ask the question:  how one is expected to know if a cycle route is or isn't recreational?
> 
> Other routes can use the approved set of roles with the same meaning. The term recreational was used to broadly indicate the scope (hiking, paddling, horse riding, cycling, inline skating, motorboat). But not OV and road routes, and other relation types, they have their own sets of roles. 
> Especially with cycling more and more signed routes are created for non-recreational uses. Since these are structurally no different from the recreational routes, it makes sense to use the same set of roles. 
> 
> AFAIK, the roles are used by mappers, not yet by data users. The main use would be to exclude "variant" members from the main route, for rendering, routing and extras such as elevation profile and gpx production. And member sorting in relation editing tools. Further use could be to render variants differently; display and use the role in data popups, lists or hierarchies; and in trip planning applications to suggest approaches, excursions, route switching and variants.
> 
> All of this was not meant for motorway relations. If it would apply, connection would be the role for a member that connects different routes, e.g. A2 to A10, and the member would be in both relations. The approach role would be used on a member representing, say, an approach: a way or a route signposted to lead traffic to a motorway.
> 
> I get the impression that the link role limps between approach and connection. Whether it is useful to add approaches and/or connections to motorway relations, I don't know.

Absolutely awesome discussion, Peter!

I understand that "these are for bike routes, not motorway relations" and "limps between" (where "limp" might also mean "is vague as to the specificity of").  I also understand "they have their own sets of roles" (even as I'm not sure what THOSE are, either, but that's OK for now).  I did not know role tagging had taken on such a rich set of semantics, but I now see that it is richer than I knew (yesterday; today is a new day).  If it's true that "not yet by data users" is true (and you assert it is), I don't feel too bad that I am far behind the curve (of knowledge of these tags, how they are used, what they mean).  We can be taught!

I remain a bit unsure of why specific distinctions between recreational and non-recreational bike routes are strictly necessary, but I'm reading wiki, I'm listening and I'm eager to learn new things.