As one could have guessed, there are basically two approaches on these cases. One approach is to store current information only and consequently delete information as soon as it becomes historic. The other approach aims at documenting the full history of all tagging and all applications ever used.
The strongest reason for the first approach is the argument that historic information might be confusing for the readers and might lead to “wrong” tagging or poor decidions regarding software deployment. Referring to my first example, one can see that the page features two red boxes. Both state that the proposed feature is abandoned. There are links to Query-to-map and Humanitarian OSM tags (marked as outdated itself), but a link to the general concept page Permanent ID featuring the background as well as an overview of the approaches is missing. On the other hand, this page serves as a documentation for the keys uuid:place and similar. This information might be lost if someone would delete the page or radically change its content (in the latter case you could still retrieve the content from the page’s history in case you know the page name).
Trash or recycle? (Image CC0)
Secondly, some users argue that outdated pages (esp. proposals) lack unique and thought-through ideas and therefore the reason to be “worth” archiving. The analogy is an outdated technical guide describing steps for installation which can not be done any more because the systems necessary to run the installation are unavailable today as technology has advanced significantly and new APIs have emerged whilst other services have creased to exist. The other side argues that understanding the history helps understanding current OpenStreetMap. An illustrative example is provided by Yahoo! Aerial Imagery. Providing the means of armchair mapping, Yahoo’s imagery paved the way for a new mapping technique at its time. The step from Yahoo-provided imagery to current Bing’s services seems small compared to tracking GPS outside only and tracing aerial imagery at home.
Facing the challenge that outdated pages are marked differently and sometimes not at all, wiki users have come up with templates like Template:Archived proposal or (more recently) Template:Historic artifact start. The templates do not solve the dispute itself but hopefully avoid misunderstandings regarding currentness.
The decision what to include in the documentation of OpenStreetMap’s history has not been made yet. There are still reverts of edits in this case. A number of pages about former render software “Kosmos” is marked for deletion. I hope we will eventually find a solution together.
The following questions need to be assessed in my opinion:
- Which pages should be kept in the wiki for documentation purposes?
- Should they be changed to reflect their historical relevance? (How?)
I would like to discuss this in the forum: https://forum.openstreetmap.org/viewtopic.php?pid=736510#p736510. Please feel free to join.