[Tagging] pipeline flow direction; was: Feature Proposal - RFC - Pipeline Extensions

fly lowflight66 at googlemail.com
Sat Nov 15 21:47:24 UTC 2014

Am 15.11.2014 um 22:38 schrieb Rainer F├╝genstein:
> f> Found one more, loop=*
> f> Some month ago we were talking on this list about flow of waterways and
> f> pipelines.
> f> The far I remember flow_direction=forward/backward/both was mentioned to
> f> tag the direction a pipeline or canal is used.
> agreed; it is better to define a tag that can also be used in other
> cases.
> I glimpsed over the pipermail web pages - can't reply directly,
> therefore a summary:
> * there are pipelines which can reverse the flow and others which
> can't. therefore it is not wise to assume "oneyway=yes" (or similar)
> by default.
> * presumably, the post by Bryan Housel ("So my reading of that was
> that pipelines imply oneway=yes") was made before the "loop" tag was
> added to the PipelineExtension proposal.
> * pipelines are usually built to transport the substance only in one
> direction. for such pipelines, it is not possible to reverse the flow
> by just pressing a button. they have to be constructed to do so, which
> some/most newer pipelines are.
> * I don't see the point of flow_direction=backward/forward on a
> pipeline. it doesn't make sense to draw the way in one direction and
> specify flow_direction=backward.
> since it (will be) a generic tag, forward/backward may make sense
> in other cases. for pipelines, I propose flow_direction=both and
> flow_direction=oneway. if the latter is disputed, using just
> flow_direction=forward (and never =backward) is a good alternative.
> * if the flow direction is unknown, just don't add the flow_direction
> tag.

The major advantage about backward/forward is the editor support once
the way direction is reversed.

Probably, do not need any value apart from "both" but if you really want
to state the flow direction forward/backward would be my choice.

cu fly

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