Re: Building a Z39.50 client and server

Stevio,
         Since you asked about how the CDL Z39.50 client (MELVYL Catalog) 
maintains state I asked one of the programmers to write a brief 
explanation. Here is his explanation:

We go to great lengths to make the Melvyl Catalog web site
state-ful (i.e., not stateless). We do that by having a UNIX
process remain active for the entire user session. When the
original connection is made to our site, our CGI program
recognizes it as the first, and it starts the UNIX process. A
session id is assigned to the process, and any time the user
clicks on something on the screen, the session id is returned
by the browser to the web server. Our CGI program sees the
session id, and it passes the incoming browser request to
the existing UNIX process. The UNIX process formulates the
HTML response and passes it back to the CGI program, which
forwards it to the user's browser.
Part of the program running in the UNIX process is a Z39.50
client, of course

Hopefully this will help you understand what the CDL does to maintain state.

Margery

At 11:54 AM 6/6/01 +0100, you wrote:
>Hi all,
>
>I'm still trying to work my way through this, any help is much appreciated!
>
>If I use a web browser as my interface to users to search, is the form on
>the web page the origin? From what I've read, Z39.50 works by maintaining a
>connection, while using the web is stateless, so how does that work?
>
>Is it the case that I would have a web app. on the server that would act as
>the origin, and it would establish a connection with the target application?
>It would then communicate with the underlying database?
>
>Also, Sebastian wrote that:
> > A Z39.50 target is not really a web application. It's a separate protocol,
> > and has a separate network port number associated to it (210, where HTTP
> > generally uses 80).
>
>How would you implement that with a web form? Is the Melvyl Catalog at the
>California Digital Library an example of this in action? See
>http://128.48.120.7/mw/mwcgi.home
>
>Thanks,
>Stephen

Margery Tibbetts
California Digital Library
University of California
1111 Franklin Street
Oakland, CA 94607-5200
(510)-987-0581
fax - (510)-763-2471

Received on Thursday, 7 June 2001 15:37:57 UTC