Communicate removed/deprecated/renamed dataset to users

[ChrisJohnNOAA]

On a slightly different note, we (CoastWatch West Coast/PolarWatch) were wondering if there could be a way to implement notification to users if they are accessing a dataset that has been removed, deprecated, or renamed (dataset ID change). It would pop up like an error message but would be different than a 404 or other error code. Rather, something customizable would be displayed that conveys that the dataset no longer available at this location, with a link leading to a page more information. Some use cases are below:

1. Notify users that a new version of a dataset is available.
2. When the source data for a dataset becomes unavailable, we can explain why and point a user to alternate datasets.

Originally posted by @CaraWilson in #209 (comment)

[ChrisJohnNOAA]

One way to do this could be to add a new dataset type (or two- one for EDDTable and for EDDGrid) that is essentially a holder for the redirect/deprecation/whatever information. Since we'd likely want to include the information in most places that datasets are displayed/used, this might be the cleanest way to do it.

[rmendels]

@CaraWilson @ChrisJohnNOAA While I understand where this request is coming from I think we should be careful about what is done. First ERDDAP™ should follow the http standard, only use http verbs and use http error codes as they are properly understood to work. Second, unless absolutely necessary, old versions of a data set should not be removed, this is in order to maintain reproducibility of results. Also, since the title can be changed without affecting the query, the title can be changed to reflect this, you know "Deprecated in favor of v2 My Favorite Satellite Data" or some such. And metadata to this affect can be added in the datasets.xml so that this is reflected in downloads and queries.

Thanks

[ChrisJohnNOAA]

@rmendels I think there could be better support for this than changing the title. Also while I understand it's not desired there are circumstances where data might no longer be available.

Maybe a standardized attribute(s) that can be set in all dataset types to indicate a deprecation or removal message. This could be a good place to include the url for the replacement dataset. I'll also consider an attribute for the new url, though I'll have to think about if that's separately useful (like for automatic redirects, but I worry about automatically directing users away from the server they are on. It might still be useful for writing error messages.). @CaraWilson, do you think more than a single admin set removal/deprecation message per dataset is needed?

[rmendels]

@ChrisJohnNOAA "Maybe a standardized attribute(s) that can be set in all dataset types to indicate a deprecation or removal message. This could be a good place to include the url for the replacement dataset."

Yes something along those lines. Some of the original suggested possibilities would entail a non-standard return if I understand the request. Plus you want something that can easily be done in the datasets.xml. Right now for a deprecated dataset we do put "Deprecated" at the front of the title.