Decide on and implement guidelines for default top-level PURLs

[cmungall]

A default top level is a purl http://purl.obolibrary.org/obo/$idspace

Some ontologies like OBI have this configured to resolve to their top page, e.g: http://purl.obolibrary.org/obo/obi

note however, that adding a trailing slash takes you to a 404 sourceforge page http://purl.obolibrary.org/obo/obi/ - I think this is counter-intuitive for most web user

Most ontologies do not have this configured, e.g. http://purl.obolibrary.org/obo/zfa (500 but to a junk amazon fall-through)

Additionally, PURLs like http://purl.obolibrary.org/obo/OBI_ go nowhere. They are frequently declared to obtain CURIEs. Should they? Maybe a 3xx to the homepage or OBI page

First question is what is our general recommendation, second is how do we implement

Recommendations for discussion:

1. Are top level PURLs only for human agents? i.e. no recommendation to implement 2-in-1 as for class PURLs. I think so.
2. Should adding a trailing slash change the location? I would say no. obi and obi/ should go to the same place
3. Should all top levels resolve for all OBO ontologies? Yes. Dashboard criteria? Possibly. Part of the point of OBO is to have everything operate the same way
4. What should be the default for ontologies that don't maintain a separate home page. Us GH or OBO page? I recommend latter as this is guaranteed to be stable whereas GH urls may change.
5. IDSPACE_ URLs 3xx to top level

Implementation

We could either (a) implement something generic or (b) standardize the ymls. I think b will be easier overall. For prospective ontologies I can add something to odk. For retrospective it should not be such hard work to update existing ones, I can take on.

I suggest taking OBI as template:

purl.obolibrary.org/config/obi.yml

Lines 256 to 257 in 83bc253

	- exact: /homepage
	replacement: http://obi-ontology.org/

This seems to be the only configuration but I'm a bit perplexed as to how the system knows to use this for a top level

Also adding

- exact: /
  replacement: <homepage url>

If we want 3xx for the IDSPACE_ urls this would need hacking in obo.yml, maaybe tackle this later?

[cmungall]

UPDATE just saw the docs on base_redirect on the README.md, sorry didn't notice this

I'm still a bit confused as to how the OBI one works, it doesn't declare this.

It seems PATO is a good example, it has a base_redirect as well as an explicit exact for /:

https://github.com/OBOFoundry/purl.obolibrary.org/blob/master/config/pato.yml

But maybe we should be encouraging DRY?