Use Web to launch apps (was Re: URL semantics)

[Zheng Wang <[e-mail]>]

We have been looking at similar issues in the Hipparch project.
I enclose here a simple description of the on-going work, and
would appeciate any comments from you.

Cheers
Zheng
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In the Hipparch project, we have been looking at issues
related to integration of applications into Web. Basically,
we would like to use the Web as the standard interface and
launch all applications from the Web.

Currently, there are two ways of launching an application
(either built-in or standalone ones) from the Web:

1) Use URL. For example,

ftp://cs.ucl.ac.uk/darpa/hipparch-ucl1.ps
mailto:[e-mail]
telnet://sonic.cs.ucl.ac.uk

2) Use MIME mapping. When an object is retrieved, an application
is started to receive the data. An example is ps files:

http://cs.ucl.ac.uk/darpa/hipparch-ucl1.ps

Although the above mechanisms work fine for some applications,
trying to extend them for applications with many parameters
(e.g. a video conferening tool) seems to be messy. 
We dont want to overload the URL too much. Also, the MIME mechanism's
"fetch and play" does not work well for real-time applications.

We are looking at a simple approach to use the Web as launch pad
for applications. We store details about launching an application
and its associated paramters into a file, and then point to the file
with a URL. When a user clicks the active element representing the URL,
the browser fetches the application description file, and starts the
application. 

What we need is a generic description of the application and its sessions
in a way independent of platforms and implementations, similar to 
the Session Description Protocol (SDP) for multimedia applications.

The generic description, which we call Standard Application Interface (SAI),
can include application name and its paramerters, operations for this session
and maybe resource requirements and other information.

For example, for a ftp session, we may have a file called hipparch.sai
which contains:

---application---
NAME: FTP
FTPSITE: cs.ucl.ac.uk
USER: anonymous
---session---
GET darpa/hipparch1.ps
GET darpa/hipparch2.ps
---resource---
SIZE: 2.5 Mbytes
TIME: after 6pm

Then we have a URL as http://www.cs.ucl.ac.uk/staff/zwang/hipparch.sai.
When a user clicks the URL, the file is fetched and the browser can
start the application specific to the platform/implementation.