VOSpace vs WebDAV

[Dave Morris]

Hi Walter,

I am one of the authors of the original VOSpace specification, along 
with Paul Harrison, Matthew Graham and Guy Rixon.

Your comparison of the main features of WebDAV and VOSpace are correct.

If what your users want is to be able to drag and drop files from their 
desktop to a remote folder using a standard file browser, then WebDAv is 
indeed probably the best protocol to use. In fact, implementing the full 
VOSpace specification will probably just get in the way. WebDav covers 
everything you need and the many existing 3rd party implementations mean 
it is a lot simpler to deploy.

You are right that asynchronous 3rd party transfers are responsible for 
much of the complexity in the VOSpace specification.

At the time, interoperable asynchronous 3rd party transfers was one of 
the reasons for developing the VOSpace specification. One of the aims of 
our project was to be able to process as much as possible 'in the cloud' 
and only transfer the final processed results to the the client desktop. 
As a result, a lot of the work on the VOSpace specification was designed 
to handle server to server transfers, rather than server to client.


Your analysis of vos: URI scheme is correct, part of its function is 
indeed to act as a name resolver service, similar to DNS.

Very similar in fact to the 'Name Mapping Authority Host' in the ARK 
scheme that Norman described. Although the steps involved in resolving 
the service URL via the registry are a bit more complex than they should 
be be due to limitations in the ivo: registry URI scheme.


Regarding the suggestion of replacing VOSpace with WebDAV plus 
extensions.

I agree - it probably is time for a fresh look at the problem, a lot has 
happened in the last 10 years (back in 2004 we still thought SOAP was a 
good idea). However, if it really is a re-write from scratch, then to 
avoid confusion and interoperability issues we should probably call it 
by a different name and use a different URI prefix.

Regards,
Dave

--------
Dave Morris
Software Developer
Wide Field Astronomy Unit
Institute for Astronomy
University of Edinburgh
--------




On 2014-05-15 06:19, Walter Landry wrote:
> Hello Everyone,
> 
> At our datacenter, we want to implement some kind of workspace for our
> users.  So the natural thing to do is to look at VOSpace and see if it
> could be bent to our needs.  However, I am also familiar with WebDAV 
> [1],
> and I am having a hard time understanding what advantages VOSpace
> brings.  Just to run down the basics about WebDAV:
> 
> 1) WebDAV supports much of the functionality in VOSpace, including
>    all of these items lifted directly from the VOSpace introduction
> 
>     * add or delete data objects
>     * manipulate metadata for the data objects
>     * obtain URIs through which the content of the data objects can be
>       accessed
> 
> 2) WebDAV is a mature, established standard deployed worldwide on a
>    variety of machines.  Every major desktop OS has WebDAV built in,
>    and you can get clients and servers for every operating system on
>    almost any hardware, including phones, tablets, and supercomputers.
> 
> 3) WebDAV has a number of implementations of the client and server in
>    every programming language you can think of.
> 
> 4) WebDAV is based on http, so it is easy to layer any of a number of
>    authentication schemes on top.
> 
> 5) WebDAV has an easily understood filesystem-like API.
> 
> In contrast, the only compelling feature of VOSpace I can think of is
> the ability to initiate 3rd party transfers.  But it would seem better
> to add a trivial extension to WebDAV rather than creating a completely
> new protocol.
> 
> Moreover, the API for VOSpace is much more complicated, with a lot of
> indirection.  The vos: URI scheme in particular feels like a
> reinvention of DNS for a benefit that I do not see.  It almost goes
> without saying that I have not seen much interest in VOSpace outside
> of astronomy.
> 
> Given all this, it feels like the best use of my time would be to
> install mod_dav on my Apache server and be done in short order.  I
> would guess that my users would even be happier than if I used
> VOSpace.  It is pretty addictive to be able to drag and drop from your
> desktop to a remote WebDAV folder using the standard file browser.
> 
> Now, I am aware that this has been discussed before.  I have also
> spoken personally with one of the authors of VOSpace.  Yet I still do
> not quite see the need for VOSpace.  Could someone enlighten me?
> 
> Thanks,
> Walter Landry
> wlandry at caltech.edu
> 
> [1] http://webdav.org/
> [2] http://www.ivoa.net/forum/grid/2007-March/001713.html
>     http://www.us-vo.org/pipermail/techwg/2005-February/000793.html