Identifying Pass-by-reference params [Re: Apps Messaging -- A New Approach

[Rob Seaman]

John Taylor replying to Mike Fitzpatrick:

>> IRAF networking's done this for 20 years:  resources can be  
>> addressed as "node!whatever" and the system internally accesses  
>> the remote resource (tape drive, file, image display, etc).  The  
>> 'whatever' could still be a URL or local file name, it could even  
>> be an appName.
>
> Maybe an approach similar to this would work better then.

The ubiquity of this approach should be emphasized.  Later  
developments like the whole "web" thing have stolen some of the  
thunder, but few (if any) alternatives are as sweeping in their  
implications as IRAF networking.  Any resource (not "some", not  
"most", not even "virtually any") can be expressed remotely.  The  
programmer would have to work - rather hard - to disable this  
feature.  (I won't belabor caveats - e.g., not permitted to cd to a  
remote disk - but none of the ones I'm aware of are intrinsic to the  
architecture.)

The IRAF CL has a foreign command escape - IRAF networking allows you  
to run the command on any host (has to have IRAF installed, of course).

Any IRAF input can be remotely targeted.  Any IRAF output can be  
remotely targeted.  A filter style command that reads input, does  
something, and writes output can move data from one remote host to  
another.  You might be better off going direct from point A to B  
without passing through C, but the point is that you can do it.

You not only can remotely copy data without firing up a facility like  
scp or ftp with special syntax - just type the same command you would  
locally - you can consult a remote df command beforehand and a remote  
directory listing afterwards to confirm the transfer.

And it isn't just the IRAF command line that benefits.  You can  
specify remote resources for any task parameters and keep remote log  
files, for instance.  The NOAO High Performance Pipeline relies on  
IRAF networking for similar purposes.

The ICE package is used to control several CCD cameras on Kitt Peak.   
Newly minted observations of the sky can be written onto remote disks  
of computers that don't have ICE installed, that don't connect to a  
CCD controller, that may not even be located on the same  
mountaintop.  Metadata for FITS headers from various sources could be  
retrieved from remotely sited central repositories.  Few observers  
might use these facilities, but the point is that these possibilities  
exist simply because ICE is layered on IRAF.  The application doesn't  
have to know anything whatsoever about networking because the system  
does.

A task that requires access to a catalog can reference an observatory  
or community-wide resource, very similar to the concept of a URI -  
except that no special server has to be installed beyond the basic  
IRAF system.

My point isn't to chat up IRAF - obviously I'm a loyal alumnus - my  
point is that such a deeply realized networking facility creates  
opportunities that you may not even know you're missing.  These are  
the sort of quasi-magical opportunities that users are going to  
expect from the VO.

Rob Seaman
NOAO