Applications Messaging Standard

[Tony Linde]

> is to explore alternatives to the use of file-based mechanisms for
> simple runtime discovery in a LAN type environment.

Can I ask if we all are talking about the same thing here? What are we
trying to discover at runtime with this file-based mechanism? 

Where the hub is and how to invoke it?
How to communicate with the hub?
What other plastic apps are running and what they can do?

As I understand it, only the first two need a file-based mechanism since the
third is only done after the hub is up and is carried out via a message to
the hub. Is this right?

And why a LAN type environment? I thought we were only looking at single
client / single user use for now?

T.

> -----Original Message-----
> From: owner-apps at eso.org [mailto:owner-apps at eso.org] On 
> Behalf Of Doug Tody
> Sent: 15 February 2007 22:21
> To: John Taylor
> Cc: apps at ivoa.net
> Subject: Re: Applications Messaging Standard
> 
> On Thu, 15 Feb 2007, John Taylor wrote:
> 
> >> IP (sockets) on the other hand, were designed for this purpose.
> >> A simple solution is to provide a well-known port for discovery
> >> (basically just a simple keyword-value cache; back it up with an
> >> environment variable or whatever to config the address)), 
> and hand-off
> >> to dynamically allocated ports for session stuff.  This 
> can all be done
> >> at the protocol level without an API, is universally 
> available, and is
> >> really not much more complex than using a file.  Probably 
> less complex,
> >> when you consider the subtle issues that files have for 
> this purpose.
> >
> > I'd be interested to know how much easier or harder it 
> would be to use IP 
> > from relatively primitive programming environments such as 
> IDL (that's not a 
> > slur on IDL...it's very sophisticated in other ways).
> 
> Well, we are after all talking about messaging software right?  Any
> system/app/language using this will already have had to figure out how
> to talk to a socket.
> 
> > One question I have is 
> > what would happen on a multiuser machine?  Would you need 
> some system process 
> > running on the one shared well-known port?
> 
> Not necessarily, but you could.  The same mechanism could be set up
> either way.  In either case the idea is one would use this only to
> provide a simple discovery mechanism, to bootstrap things up, then
> hand off to other facilities.  Having something which at the most
> basic level can be accessed by multiple accounts could be a useful
> thing it itself, as sometimes resources which need to discover each
> other and communicate are running under separate accounts.
> 
> Clearly there are issues which need further thought, but the point
> is to explore alternatives to the use of file-based mechanisms for
> simple runtime discovery in a LAN type environment.
> 
>  	- Doug
> 

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