Discover and start VO Applications (SAMP compatible)

[Laurent Bourgès]

 Dear VO members,

We are working at the JMMC on client applications for the optical
interferometry using VO and in particular SAMP : Aspro2 (interferometric
observation preparation tool), LITpro (model fitting) and SearchCal (search
star calibrators for a particular target). Our applications use standard
message types (load.votable) and custom messages to deal with our particular
needs.

We are looking for a solution to launch VO applications that are able to
deal with SAMP messages directly without asking the user to start manually
required applications ...
Indeed, there is no standard mean to launch a SAMP application from another
client application :
- Aspro2 => SearchCal and LITpro
- SearchCal => Aspro2, Aladin and any SAMP application supporting VOTable
containing a star catalog
- LITpro => topcat (VOTable and FITS)

One solution can use the fact that all these applications are supporting
Java Web Start : it is possible to launch such applications using the
command : 'javaws http://host/application.jnlp'.

However it requires that the client application has the knowledge / meta
data like :
- application name
- application URL (jnlp)
- description
- supported SAMP message types
...

It looks like a registry entry describing any VO SAMP application and also
extends SAMP Application meta data.

The well known Aladin (CDS) has already this feature using GLU (CDS specific
registry implementation).
Moreover it can also install and launch any application using a custom
command line.

Here is a screen shot of the VOTool window :
[image: Aladin VO Tools]

I would like to know if you consider this feature should be covered by VO
standards.

According to me, it has several impacts on existing standards :
- Registry : provide VO applications descriptions with SAMP capabilities :
SAMP capabilities are already described by the SAMP protocol but only
available at runtime (via the hub).
        What is the status of the VOApplication extension to VOResource ?

"VOApplication is a registry extension schema that allows one to register
applications, tools, and libraries. A working draft of a document defining
the extension schemas for describing applications is under development at
RegDMApplications<http://www.ivoa.net/cgi-bin/twiki/bin/view/IVOA/RegDMApplications>.


At the Fall 2009<http://www.ivoa.net/cgi-bin/twiki/bin/view/IVOA/InterOpNov2009Reg>Interop,
the Registry Working Group agreed to table the development of this
schema until a stronger driver emerges. Contributions and comments are still
welcome; *we are particularly interested in use cases that need the ability
to dynamically discover applications*."

 - Application / SAMP : The SAMP hub could handle the discovery of
applications supporting SAMP message types (registry client) and launch the
needed application. This requires important changes in existing SAMP
libraries but applications using those could take advantage of this new
feature.


Finally, having VO applications in the registry could help us providing a
new client or web application to discover, browse and install VO
applications to novice users and help them using the VO (like ubuntu
software center : http://en.wikipedia.org/wiki/Ubuntu_Software_Center).

Best regards,
Laurent

-- 
Laurent Bourgès
Software engineer
JMMC - LAOG - CNRS
France
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