Abstract
     
     Online  linkages between Web servers  and  databases
     are  highly  demanded  and appreciated  by  the  WWW
     surfers. Also, more and more owners of databases are
     interested  in  making available  their  information
     resources   to  wider  communities  and   consumers.
     Therefore, tools for establishing interfaces linking
     the Web servers with database management systems are
     requested.  Towards this end, some of  big  database
     software   vendors  have  already  provided   tools;
     however,  the public domain database software,  such
     as  well-known  and  applied by  widely  agriculture
     concerned  agents MicroCDS/ISIS, still  need  to  be
     enhanced.  This  paper  reports  the  results  of  a
     project  which  was aimed at the  development  of  a
     methodology  and tools for interfacing MicroCDS/ISIS
     with the Web servers in the Unix environment.


1. Introduction

The  World  Wide Web (WWW) has been conceived as a  method  for
distributing information to a widely distributed users. The Web
has,  indeed,  been  exceptionally good for that  purpose.  Web
pages  began  to  become interactive - but the interaction  was
often  simply  a  new  way  to get the  same  information.  The
limitations  of  Web  distribution were all  to  apparent  once
designers  began to try to stretch the boundaries of  what  the
Web  can do [NF95]. One of the successful novelties which  made
the Web more powerful and appealing was the introduction of the
Java  language  and  the so called applets,  i.e.  dynamic  and
interactive  programs that can run inside a Web page  displayed
by  a Java-capable browser. Another one, which is a subject  of
this  contribution, is the idea of dynamic (online) interfacing
of  the  Web with a database running behind the www pages.  The
dynamism  means  that any modification of  a  portion  of  data
within  the database is immediately reflected on the  www  page
when  the portion is requested by a reader of the www document,
and  vice versa, the database can be updated from the www  page
by the reader.

Efforts  have  been made to implement this idea for  commercial
products  (e.g.  the  Oracle  link to  Web  servers,  Microsoft
Windows  NT-based Web server linked with the  MS  SQL  database
software ). Yet, very little has been done in terms of  popular
public domain software, mainly because the development of tools
for  establishing  links between the Web servers  and  database
management  systems  is rather a costly venture.  One  of  such
software  is MicroCDS/ISIS (developed and distributed  free-of-
charge  by  UNESCO) that is widely applied in Poland and  other
Central Europe countries.

The  Institute  for Computer and  Information  Engineering  has
developed a technology allowing one for dynamic interfacing the
www  documents (written in the HTML language) and MicroCDS/ISIS
databases. The dynamism, however, works in one way only because
the  changes of the database’s state can be seen from  the  www
page  - but there is no feature for updating the database  from
the www page.

One  can find an application of the developed technology on the
site

     http://intib.unido.org/isis

The  database, which is available for retrieval,  installed  on
this   site  is  the  Industrial  Development  Abstracts  (IDA)
database  carried out by United Nations Industrial  Development
Organization.  Also,  an  online  catalogue  of   the   library
management  system  running Österreichische  Forschungsstiftung
für  Entwicklungshilhe (OeFSE) in Vienna has been implement  by
means  of this technology. One can browse the catalogue on  the
site

     http://oefse.ifs.tuwien.ac.at/cgi-bin/lib

At  present,  preparatory  work based  on  the  presented  here
technology is carried out to make available via the web part of
the   information  system  on  agriculture  research   projects
(SIBROL) operated by the Central Agriculture Library in Warsaw.


2. Working principles

Fig.1 displays the architecture of the WWW - ISIS interface. It
is   based   on  the  forms  feature  of   the  HTML  language.
Interfacing consists in executing a CGI  program [GL96] started
by  the  HTTP  server  process.  The  database  backend  is   a
MicroCDS/ISIS  ver.  3.0  application  running   on   an   AT&T
compatible Unix.



The  server side of the interface was tested on a Linux machine
(kernel 1.3.12 with ELF support) [EW95] running a NCSA HTTP 1.3
server. The client side of the interface was tested on a number
of  www  browsers, including, but not limited to: Netscape  1.2
for  MS-Windows, Netscape 2.0 for Unix (Linux,  BSD,  Solaris),
Lynx (AIX). Note that your www browser has to support HTML  v.2
forms in order to make use of the WWW - ISIS interface.

The interaction between the client (www browser) and the server
when querying the database and retrieving hits goes as follows:

1.   The client downloads a query form.

2.   The user fills relevant fields in the retrieved form .

3.   The user submits the filled-in form to the server.

4.    The  WWW  server  starts the postisis process  as  a  CGI
      program.

      The postisis program (that is a core of the developed
      technology) has been written in ANSI C; standard ANSI
      libraries have been used. The program was compiled by GNU 
      C compiler ver. 2.6, and linked with the standard Unix C
      library (libc).

5.    Postisis either generates a database query to the WWW -
      ISIS backend (if the “search” button was pressed), or 
      generates an on-line form for further processing 
      (“list”, “ok”, “more”, “back” or “cancel” buttons were 
      pressed).

6.    Postisis passes its output to the www server for  further
      interpretation

7.    The www server returns the postisis output to the client’s
      browser for displaying.


3. Competitive features of the technology

A  unique  feature  of  the technology  developed  consists  in
establishing  a  dynamic  link  between  a  database  and   its
counterpart  being  a  www page. The update,  if  any,  of  the
database can be instantly seen on the www page, if requested by
the  user. None part of the database is kept on the www  server
side.   Therefore,  there  are  no  problems  with  maintaining
consistency between the master database and its replica on  the
www server side, and less disk space is allocated, which is the
case for some other solutions.

Noteworthy,  due  to  some  advanced  facilities  designed  and
developed   by  the  Institute  for  Computer  and  Information
Engineering the MicroCDS/ISIS database applications provided by
the  Institute  go far beyond what is offered by  the  standard
MicroCDS/ISIS software (as delivered by UNESCO), in particular,
various  look-up tables which contain key-words or  descriptors
supporting  the formulation of queries are given to the  user’s
disposal. These tables are also brought from the database up to
the  user by the interface described above. Thus, the user  can
pick up the terms from the tables in order to set up a query.

Due  to a local standardization and modularity of the developed
technology (“LegoLand”), interfacing a database with a www page
is relatively a simple and fully reliable task; however, it has
to  be  preceded  by  migrating the application  to  the  Linux
environment  (if it currently runs under DOS) and  establishing
the www page.


4. Further work

In order to make the developed interface more attractive to its
prospective  customers, the following tasks have  already  been
started.

1.   Migration of the developed technology to the Windows NT
     environment that is gaining popularity among the LAN
     administrators [VN96]. At the moment, experiments are 
     carried out with Microsoft’s Internet Information Server 
     and MicroCDS/ISIS applications running in the Windows NT 
     environment.
  
2.   Enhancing the dialog interface by adding simple Java
     applets, and re-writing some of the C programs into Java.
  
3.   Allowing one for transferring multimedia objects from
     MicroCDS/ISIS to the Web server.


The authors of this paper can be reached by: voice: 

M. Muraszkiewicz - voice/fax:  (+4822) 447931; 
e-mail: mietek@mimuw.edu.pl; 

H. Rybinski - (+4822) 6516226, fax: (+4822) 6516222; 
e-mail: rybinski@mimuw.edu.pl


5. References

[EW95]   Ewing M., Running Linux CD-ROM Companion, O’Reilly &
         Associates, 1995.

[GL96]   Gundavaram S., Dyung Le, CGI Scripting on the World
         Wide Web: On-the-Spot Information, O’Reilly &
         Associates, 1996.

[NF95]   Niederst J., Freedman E., Mui L., Web Design for
         Designers, O’Reilly & Associates, 1995.

[VN96]   Vaughan-Nichols S., Spinning the Corporate Web,
         Byte, pp. 113-116 May 1996.