Hi all,
Why is it headed as 'Attic Data'? Why is there no explanation of it's meaning? After too much time using google I find it means old information. Why not say that? Wouldn't 'historical snapshot' be a bit clearer?
It is on purpose not named 'historical'. It would have become a homonym, and having homonyms is always asking for trouble.
There is a whole project, named OpenHistoricalMap that collects data of features that have existed in human history, like Roman streets. That's history. It's a firm definition we cannot and should not overturn. In particular, OpenHistoricalMap does use for a good reason tags like start_date and end_date independent of when a representation is written to the database.
What we have here are 'outdated representations' of more or less unchanged objects on the ground. It may sometimes reflect changes on the ground, but most of changes happen due to mapping refinement or vandalism. Hence, we need a different notion to express that we refer to representations that were current at an earlier point in time.
It is then indeed reused from the well-known VCS terminology: a VCS keeps as well the extra data necessary to turn the controlled system back to consistent state at an earlier date. That kind of data is called "attic" there, and it is precisely the same concept as we have here.
A fun fact: the whole attic feature of Overpass is designed on the same decisions as the CVS storage. It turns out to be quite useful. We are as disk-space-constraint now as the users were for source code at the time CVS was developed in 1990.
Best regards, Roland _______________________________________________ talk mailing list talk@openstreetmap.org https://lists.openstreetmap.org/listinfo/talk
