VOSpace vs WebDAV

[Walter Landry]

Markus Demleitner <msdemlei at ari.uni-heidelberg.de> wrote:
> Hi,
> 
> On Thu, May 15, 2014 at 11:16:49AM +0000, Paul Harrison wrote:
>> ubiquity of this protocol and the ivo: and vos: just do not have
>> the client support - if we could reinvent/reinterpret ivo: and vos:
>> URNs via redirects off a central http://ivoa.net/ service URL  so
>> that you could use curl to get resources, I think that it would be
>> a very good thing?
> 
> I don't know about vos: yet (though my feeling is that if we can do
> what we do with VOSpace using WebDAV+conventions, I'd find that
> nifty), but for ivo: that central redirector (that would in principle
> be trivial) won't work as there's not nearly a 1:1 relation between
> ivo: and https?:  Indeed, in VOResource things work like this:
> 
> A resource (referenced by an ivo URI)
>   has 0..n capabilities, each of which has
>     0..n interfaces, each of which has
>       0..n accessURLs
> 
> (with RegTAP, we're pushing for 1:1 between interfaces and
> accessURLs, but even then we have 1:n^2 between ivo and http).
> 
> So, a simple redirector won't cut it, and frankly I think plain HTTP
> (in the sense of "curl is all you need") just won't do as a Registry
> client protocol, even with accept: and all the other fancy stuff.

I must be missing something.  URI's can be hierarchical.  Why can
there not be a 1:1 match between interface and URI?  We do have to
make a conscious decision to do it, but I am missing the technical
issue.

In general, I do not understand why a new central registry is going to
work any better than the http URL's.  Yes, URL's go bad and require
maintenance.  But anyone who fails to make their data discoverable
through Google is probably not going to be attentive to updating
entries at ivoa.net.  URL's are also easier to deal with in programs
and do not stop working if a server on a different continent is
having a bad day.

We already have experience with this with URL shortening services.  If
I see a URL like

  http://example.org/VO/TAP/

and it stops working, I can eventually figure out that

  http://example.org/TAP/
  
is the new URL by browsing example.org.  But if I see

  http://goo.gl/AtsaT18

I do not know anything about it.  The only thing that really works is
if we use the existing Internet structure of DNS and search engines.
They are far more reliable than anything we could hope to build.  For
example, properly registering our Simple Cone Search is still mired in
confusion.  In contrast, Google found out about it almost as soon as
we published it.

Cheers,
Walter Landry