Future Trends for a Global Object Web

Philippe Merle
Christophe Gransart
Jean-Marc Geib

Laboratoire d'Informatique Fondamentale de Lille - URA CNRS 369
Université de Lille 1, Bat M3
59655 Villeneuve d'Ascq Cedex - France
Phone: (33) 20 43 47 21
Email: {merle, gransart, geib}@lifl.fr

WWW and Corba

The future of distributed client/server computing will consist of WWW and Corba environments. First, WWW is the "killer application" [Black94] of the 1990s thanks to its user-friendly uniform interface to access any distributed resource. Second, Corba is the next generation of middleware thanks to its single uniform object-oriented view of distributed and heterogeneous systems integration.

But WWW users ask for many extensions: changing HTTP protocol, integrating new kinds of Web resources, extending Web browsers. This problem can be overcome with a uniform model of resource interface, and transportable front-ends, that could be generically integrated in WWW. The Corba object-oriented approach offers good properties to encapsulate and structure Web components under a same paradigm. It brings modularity, flexibility and abstraction to the diversity of needed features encountered into WWW. For instance, IIOP could replace HTTP to access any distributed Web object.

Moreover, a parallel can be made between a set of objects and an hypertext-linked set of resources. Hypertext navigational model can be used to navigate through Corba objects, and so, WWW can be used as a uniform ``any-object'' presentation and invocation GUI.

CorbaWeb

The CorbaWeb environment [Merle96] aims at providing a generic gateway between the WWW server side and Corba. This enables to navigate over and invoke Corba objects as easily as users navigate over the Web.

With CorbaWeb, a WWW client can navigate through Corba object links using dynamically generated URLs for each object. CorbaWeb uses a set of scripts to access Corba objects: Exec to execute any operation on any object, Interface to automatically generate HTML Forms from IDL interfaces and View to generate an HTML representation of the object state (via specific display scripts stored in the CorbaWeb Repository). New scripts can be designed to extend the CorbaWeb environment.

Currently, these scripts are CGI programs written in CorbaScript. CorbaScript is an interpreted scripting language to apply any operation on any Corba object. Objects are dynamically invoked through the DII: Invocations are checked thanks to the object IDL signatures retrieved from the Interface Repository.

Then, CorbaWeb allows WWW clients to access, display and invoke any Corba object, so new WWW resources could be implemented by Corba objects. CorbaWeb is experimentally used to access the medical information of the Hospital Center of Lille.

We submit the "Generic Object Navigator" as the next generation of Web browsers. Web browser features will be Corba objects dynamically plugged in the GON. Then, GON will be an extensible dynamic browser which allows the invocation of any Corba object through the same hypertext paradigm like current browsers.

Thus, we argue that WWW and Corba will merge to provide the next infrastructure for distributed computing.

Bibliography

[Black94] A.P. Black and J. Walpole,
Objects to the rescue! or httpd: the next generation operating system,
ACM-SIGOPS 94, Sixth SIGOPS European Workshop,
Wadern Germany, September 1994.
<URL:ftp://sigops.informatik.uni-kl.de/sigops/papers/S.Postscript.Black>

[Merle96] P. Merle, C. Gransart and J.M. Geib,
CorbaScript and CorbaWeb: A Generic Object-Oriented Dynamic Environment upon CORBA,
In Proceeding of TOOLS Europe'96, Palais des Congrès, Paris,
Prentice-Hall, February 96.
<URL:http://www.lifl.fr/~merle/papers/TOOLS96.ps.gz>