Troeps knowledge servers: technical aspects
The similarity between Web pages and objects is quite obvious and the
mapping from one to another is straightforward. The WWW mode of browsing
is thus a natural interface to object systems.
Knowledge bases can be used as Web servers whose skeleton is the
structure of formal knowledge (mainly in the object-based formalism)
and whose flesh consists of pieces of texts and images tied to the
objects. Turning a knowledge base system into a Web server is easily
achieved by connecting it to a port and transforming each object
reference into an URL. If the knowledge base is already documented by
Web pages, the latter remain linked to or integrated into the pages
corresponding to these objects.
Tree display and manipulation
The missing items of classical knowledge base browsers are the graph display
of hierarchical data (e.g. class trees or graphs). An
of Thomas Koch's
written in Java is used in order to display
our own class hierarchies. More development on colour and behaviour of
the nodes is required.
On the fly page generation
Troeps knowledge servers use the CGI (Common Gateway interface)
technology in order to
get queries from httpd. For the technics, the whole system is
made of two processes:
- A Troeps
server which is a talk executable running as a daemon
and listening to a particular TCP port;
- A CGI script which is a compiled C program whose role consists
in rooting the http queries to the
server and redirecting the output to the standard output.
The reason for this architecture is that Talk executables are
too fat and require too much time to start and load knowledge
bases. So they are started at boot-time, with loaded knowledge
bases and requested by the CGI script launched at query time.
Another good advantage found afterward is that the Troeps servers
does not have to be launched on the same location as the HTTP server.
The CGI script just has to be recompiled in order to
change the machine and port to which it will communicate (and this
remaining hidden from the external users). This is a great advantage
over the W3 API approach since it is not necessary to launch HTTP
servers on many computers.
It is possible to get the source code at
The code can be used to build your own server (if you can compile it with
talk) or as an example to build a similar server.
Made by Jerome . Euzenat À inrialpes . fr on 04/05/96
Maintained by Jérôme Euzenat;
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Modified on 17/06/98