Update Policy_for_OBO_namespace_and_associated_PURL_requests.md

[ramonawalls]

I added a new section on PURL maintenance, resolves issue #344. I also updated the request example to one that is on GitHub. Not sure is there is an issue for that.

@cmungall or @jamesaoverton please check and commit if you approve.

[jamesaoverton]

Thanks Ramona. This is a good first draft but I'd like to get more precise.

On the call today we focused on the "product" PURLs (the PURLs for a project's primary OWL and OBO files) which are particularly important. Breakage with these has caused problems downstream with portals. We have a number of tracker items about these problems, and we want to have a clear policy for stepping in to make changes. The products are listed in the registry entries, and configured in the PURL entries (in the other repository).

By "doesn't work" I think we mean that the product PURL does not resolve to a valid OWL or OBO file. By "obsolete" I think we mean removing these PURLs from our lists of all products, so that downstream consumers don't automatically try to fetch them. @cmungall might have something else in mind. I'd prefer to be more specific about the steps we'll take to contact maintainers, and how long we'll wait for a response.

Sorry to be pedantic, but getting clear now might save us headaches later.

[cmungall]

We need to document our obsoletion better, but it's this:

• we add a is_obsolete tag to the yaml-md in this repo. This makes the ontology appear in strikeout on the page
• we don't touch the purls, they continue to redirect as before, whether it's to a 404, invalid syntax, etc

[cmungall]

I'm merging as this is a good incremental improvement, leaving the parent ticket open