Different Kinds of ServerFirst on our tour of the web , let's
see what the different types of existing
server look like using a W3 browser.
(for the fancy demos, skip ahead
FTPAn FTP server , for example, is simply
presented as a hypertext list. The
user does not have to know anything
about FTP. This example is a server
which has postscriptr copies of preprints
of physics papers. We can fllow through
the directory structure to the preprints
directory , to the preprints from
Rice , into the ps directory which
I happen to know contains postscript
files, and find a particular preprint
of a physics paper .
GopherLooking at a Gopher server is very
similar. Gopher is like WWW except
that there is no hypertext: anything
is either a plain document or a menu.
Here we see an example of a gopher
menu, and you can see that there
are extra menu items which have been
introduced to look like headings.
NewsWhen a WWW browser reads news, it
uses hypertext to give instant links
between related articles and newsgroups.
Looking for example at WWW's own
newsgroup, comp.infosystems.www ,
let's select a reply message -- one
starting with "Re:". [I can't leave
you a link to this as news messages
are deleted with time, so you have
to pick one.] Notice that at the
top of the article there is a link
back to the newsgroup. Also, there
is a link to any article references.
If you are lucky with your choice,
you will see a link within the text
"in article <blah>, somebody writes".
This is a good example of W3 software
making links out of existing information.
W3 serversLastly, let us look at some real
hypertext sepcifically written for
W3. Here is the "STING" Software
technology Interest Group service
. We are presented with various options
as to how we would like to search
for data. Let's suppose we want
to know what "objective" means in
"objective C". We first select STING
and give "Objective" as a search
word. We get back a summary of what
STING has found for us . As STING
is relatively intelligent, it gives
us pointers to other good places
to look too. We chose the software
engineering glossary entry , . This,
like the search results, is a "virtual"
hypertext document, in that it has
been generated on the fly by a server.
It isn't written in a disk file anywehere.
It is relatively easy to write servers
to generate hypertext spaces like
this, allowing complex information
to be very simply presented to a
user with no special skills.
We have seen how a W3 client gives
access to a vast range of existing
data from existing servers, but how
the hypertext data from HTTP (native
W3) servers is a much richer and
easier to explore.
(Part of the W3 seminar . on to "what
can be done" )