VOSpace 2.1 and view=data

[Brian Major]

Hello,

If you were present at the GWS II session in Stellenbosch you will remember
that the issue of being able to construct a single, shareable VOSpace
download URL was raised.
Currently, the recommended way of doing this is by constructing a
/synctrans request with the REQUEST=redirect parameter included:

curl "https://server.example.com/vospace/synctrans
    ?TARGET=vos://example.com~vospace/mydata1
    &DIRECTION=pullFromVoSpace
    &PROTOCOL=ivo://ivoa.net/vospace/Core#httpsget
    &REQUEST=redirect
    &SECURITYMETHOD=ivo://ivoa.net/sso#tls-with-certificate”

This works just fine and offers a lot of flexibility but is cumbersome.  It
is not intuitive to construct, and the URL doesn't end with the filename,
thus causing some clients (such as wget) to name the downloaded file
something strange like 'tls-with-certificate' because, by default, they
ignore the content-disposition header.

The current 1.1 spec says view=data is deprecated.

curl "https://server.example.com/vospace/nodes/mydata1?view=data"

If I remember correctly, these are some of reasons for deprecation:
    1)  The behaviour overlaps with what is offered by /synctrans
    2)  Because the URL ends with ?view=data, it suffers from the wget
problem I noted above.
    3)  There is ambiguity about the security method.  Just because the
initial request was over https, you cannot assume a certain security method
(such as client certificates).  The security method cannot be determined by
the URL scheme.

That said, it is a much more attractive URL because it is RESTful (node
hierarchy is in the URL path) and makes logical assumptions for the
remaining parameters.  (direction is download, protocol is HTTP or HTTPS,
yes follow redirects).

So, for the purpose of being able to provide users with a single, shareable
download URL, I'd like to open the discussion on view=data again.  Some
questions:

- Should VOSpace users require a smart client that understands transfer
negotiations, or should simple HTTP clients such as curl and wget work?
 (For downloads only--uploads and server to server transfers are certainly
too complex.)
- Should VOSpace support view=data on the /nodes resource?
- Is there an alternate way of offering a shareable download URL?  (By
shareable I mean a URL that you can give collaborators and will work for as
long as the node exists.)

Cheers,
Brian



-- 
Brian Major

Canadian Astronomy Data Centre
Centre canadien de données astronomiques

National Research Council Canada
Conseil national de recherches Canada
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