Some organization needs to commit to long-term archiving. I'd recommend asking a university library and perhaps the Internet Archive.
MO needs a policy for how to deal with deletion, since archiving is useless if material can be deleted from the archives. The simplest solution is to preserve everything, but that has several drawbacks: you'll be preserving some total garbage, and crackpots may take advantage of it (even if their work is immediately deleted from the live MO site, it will be permanently accessible and citable in the archives). On the other hand, you need to make sure nothing of any actual value could ever be deleted from the archives. One solution could be to have a one-month window, and permanently archive anything that survives for a month on MO without being deleted.
It's also worth thinking about what else should be preserved. For example, comments certainly need to be archived, since they may play an important mathematical or historical role. Presumably it's safest to archive everything, even relatively superficial things like upvotes on comments.
MO's handling of permalinks is suboptimal for citations. For example, the "share" link automatically appends the user ID for tracking purposes (to award badges to those whose shared links are widely used), which is probably not what someone looking for a citable link wants. There are permalinks for every revision, but they are a little less obvious to find, and they link just to the specific text in question (for example, http://mathoverflow.net/revisions/153731/1https://mathoverflow.net/revisions/153731/1 requires several clicks before you can find any of the answers). It would be great to have a more flexible system that archives snapshots at a given time while still making it easy to see any related material and to see any later updates. For example, an archive link could show the whole question/answer page as it looked at the time that the link was made, with a prominent option to see what happened at other times. Adding the full time to the permalink could be cumbersome, but all that's needed is a numbering of the changes made to each page. Getting this working is not conceptually difficult, but it could be time-consuming, and there are a lot of irritating aspects. (For example, how much do we care about things like chronology of votes? Is it possible that someone citing an MO question would refer to something like "the most upvoted answer" in a way that couldn't be understood later without knowing the voting history and when the assertion was made? On the other hand, changing the recommended permalink every time someone votes seems silly.)
If all this is taken care of, then we could largely solve the citation problem by adding a "citable link" button, maybe even replacing the current "share". It would give an archival permalink together with a recommended citation format. (Of course there might still be psychological issues regarding which sorts of citations are considered acceptable, but these steps would accomplish about as much as I think MO reasonably could in the near future.)
Some organization needs to commit to long-term archiving. I'd recommend asking a university library and perhaps the Internet Archive.
MO needs a policy for how to deal with deletion, since archiving is useless if material can be deleted from the archives. The simplest solution is to preserve everything, but that has several drawbacks: you'll be preserving some total garbage, and crackpots may take advantage of it (even if their work is immediately deleted from the live MO site, it will be permanently accessible and citable in the archives). On the other hand, you need to make sure nothing of any actual value could ever be deleted from the archives. One solution could be to have a one-month window, and permanently archive anything that survives for a month on MO without being deleted.
It's also worth thinking about what else should be preserved. For example, comments certainly need to be archived, since they may play an important mathematical or historical role. Presumably it's safest to archive everything, even relatively superficial things like upvotes on comments.
MO's handling of permalinks is suboptimal for citations. For example, the "share" link automatically appends the user ID for tracking purposes (to award badges to those whose shared links are widely used), which is probably not what someone looking for a citable link wants. There are permalinks for every revision, but they are a little less obvious to find, and they link just to the specific text in question (for example, http://mathoverflow.net/revisions/153731/1 requires several clicks before you can find any of the answers). It would be great to have a more flexible system that archives snapshots at a given time while still making it easy to see any related material and to see any later updates. For example, an archive link could show the whole question/answer page as it looked at the time that the link was made, with a prominent option to see what happened at other times. Adding the full time to the permalink could be cumbersome, but all that's needed is a numbering of the changes made to each page. Getting this working is not conceptually difficult, but it could be time-consuming, and there are a lot of irritating aspects. (For example, how much do we care about things like chronology of votes? Is it possible that someone citing an MO question would refer to something like "the most upvoted answer" in a way that couldn't be understood later without knowing the voting history and when the assertion was made? On the other hand, changing the recommended permalink every time someone votes seems silly.)
If all this is taken care of, then we could largely solve the citation problem by adding a "citable link" button, maybe even replacing the current "share". It would give an archival permalink together with a recommended citation format. (Of course there might still be psychological issues regarding which sorts of citations are considered acceptable, but these steps would accomplish about as much as I think MO reasonably could in the near future.)
Some organization needs to commit to long-term archiving. I'd recommend asking a university library and perhaps the Internet Archive.
MO needs a policy for how to deal with deletion, since archiving is useless if material can be deleted from the archives. The simplest solution is to preserve everything, but that has several drawbacks: you'll be preserving some total garbage, and crackpots may take advantage of it (even if their work is immediately deleted from the live MO site, it will be permanently accessible and citable in the archives). On the other hand, you need to make sure nothing of any actual value could ever be deleted from the archives. One solution could be to have a one-month window, and permanently archive anything that survives for a month on MO without being deleted.
It's also worth thinking about what else should be preserved. For example, comments certainly need to be archived, since they may play an important mathematical or historical role. Presumably it's safest to archive everything, even relatively superficial things like upvotes on comments.
MO's handling of permalinks is suboptimal for citations. For example, the "share" link automatically appends the user ID for tracking purposes (to award badges to those whose shared links are widely used), which is probably not what someone looking for a citable link wants. There are permalinks for every revision, but they are a little less obvious to find, and they link just to the specific text in question (for example, https://mathoverflow.net/revisions/153731/1 requires several clicks before you can find any of the answers). It would be great to have a more flexible system that archives snapshots at a given time while still making it easy to see any related material and to see any later updates. For example, an archive link could show the whole question/answer page as it looked at the time that the link was made, with a prominent option to see what happened at other times. Adding the full time to the permalink could be cumbersome, but all that's needed is a numbering of the changes made to each page. Getting this working is not conceptually difficult, but it could be time-consuming, and there are a lot of irritating aspects. (For example, how much do we care about things like chronology of votes? Is it possible that someone citing an MO question would refer to something like "the most upvoted answer" in a way that couldn't be understood later without knowing the voting history and when the assertion was made? On the other hand, changing the recommended permalink every time someone votes seems silly.)
If all this is taken care of, then we could largely solve the citation problem by adding a "citable link" button, maybe even replacing the current "share". It would give an archival permalink together with a recommended citation format. (Of course there might still be psychological issues regarding which sorts of citations are considered acceptable, but these steps would accomplish about as much as I think MO reasonably could in the near future.)
I'd be inclined against anything that could be interpreted as trying to make the mathoverflow archives look or behave like a journal. (E.g., assigning an ISSN, using volume or issue numbers, giving each post a DOI, etc. Strictly speaking, DOIs have nothing to do with journal articles, but that's by far the most common use case in mathematics, so it would look like it's imitating journals.) I think this could annoy people by seeming like MO is trying to become more citable by pretending to be something it's not.
On the other hand, I think the citation issues can be resolved without any journal-like features. Here's what I think is needed:
Some organization needs to commit to long-term archiving. I'd recommend asking a university library and perhaps the Internet Archive.
MO needs a policy for how to deal with deletion, since archiving is useless if material can be deleted from the archives. The simplest solution is to preserve everything, but that has several drawbacks: you'll be preserving some total garbage, and crackpots may take advantage of it (even if their work is immediately deleted from the live MO site, it will be permanently accessible and citable in the archives). On the other hand, you need to make sure nothing of any actual value could ever be deleted from the archives. One solution could be to have a one-month window, and permanently archive anything that survives for a month on MO without being deleted.
It's also worth thinking about what else should be preserved. For example, comments certainly need to be archived, since they may play an important mathematical or historical role. Presumably it's safest to archive everything, even relatively superficial things like upvotes on comments.
MO's handling of permalinks is suboptimal for citations. For example, the "share" link automatically appends the user ID for tracking purposes (to award badges to those whose shared links are widely used), which is probably not what someone looking for a citable link wants. There are permalinks for every revision, but they are a little less obvious to find, and they link just to the specific text in question (for example, http://mathoverflow.net/revisions/153731/1 requires several clicks before you can find any of the answers). It would be great to have a more flexible system that archives snapshots at a given time while still making it easy to see any related material and to see any later updates. For example, an archive link could show the whole question/answer page as it looked at the time that the link was made, with a prominent option to see what happened at other times. Adding the full time to the permalink could be cumbersome, but all that's needed is a numbering of the changes made to each page. Getting this working is not conceptually difficult, but it could be time-consuming, and there are a lot of irritating aspects. (For example, how much do we care about things like chronology of votes? Is it possible that someone citing an MO question would refer to something like "the most upvoted answer" in a way that couldn't be understood later without knowing the voting history and when the assertion was made? On the other hand, changing the recommended permalink every time someone votes seems silly.)
If all this is taken care of, then we could largely solve the citation problem by adding a "citable link" button, maybe even replacing the current "share". It would give an archival permalink together with a recommended citation format. (Of course there might still be psychological issues regarding which sorts of citations are considered acceptable, but these steps would accomplish about as much as I think MO reasonably could in the near future.)
Monthly or weekly static versions would be much easier, and they would certainly help solve this problem, but the limited time resolution would be a problem. Ideally, a "citable link" button should immediately produce an archival link that reflects what you see now, rather than an approximation that may be a week or more off.