Stefan Nagy
@fkv: Thanks for your comment – it was a good reason to make up my mind. So this is my point of view now: The redundant information makes sense, because it can help us a lot when political decisions regarding maximum speeds are made. And I agree with westnordost (see https://github.com/westnordost/StreetComplete/issues/492#issuecomment-326080750) that "the convention is that source:* describes the source of the tag. An implicit speed limit type/zone is not a source". So I'll use maxspeed:type=AT:zone30 instead of source:maxspeed=AT:zone30, source:maxspeed=AT:zone:30 or source:maxspeed=zone from now on. In other words: I decided to use the same tagging scheme as westnordost in StreetComplete.