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(a)(i)A World Wide Web server has a set
of legal URLs that it makes available to WWW clients.Normally those
files are images, HTML files, or other static documents. When the
client asks to supply such static documents, the server simply returns
the documents.However when the client asks fo a URL that points to
a CGI application,a different process occurs. Describe the three steps
in this process. [6 marks ]
• The WWW client sends a request to the HTTP server (1), giving
the name and location of the CGI application (1), providing parameters
if necessary.
• The HTTP server starts the application (1), providing extra
information to the CGI application, including parameters (1).
• When the CGI application terminates, all output produced by
the application is returned to the client (1). Additional information
is added to the HTTP header by the CGI before the output is returned
(1).
(ii)Give an example of
a common task using the WWW that requires a CGI
application, clearly stating why the CGI application is needed.[2
marks ]
A telephone directory which maintains a large database. When users
want
information, they send a query to a CGI application which acts as
an interface to the database. The CGI application accesses the database
and generates a WWW page containing the information requested in the
query. If a CGI application were not used, the telephone directory
would need to consist of many WWW pages, one for each entry in the
database.
(1) for appropriate example; (1) for explanation as to why it is needed.
(iii)Briefly explain any
two points that should be considered when choosing a
language for developing a CGI application.[4 marks ]
• Interpreted vs compiled (1): programs in compiled languages
run faster;
interpreted lang ages are more flexible (1)
• Portability vs modifiability (1): a stable language that is
not going to change much in the long term and which does not rely
on propriety hardware and software is preferable (1)
• Development time (1): WWW sites typically need to be produced
rapidly so that the information to be presented can be made available
as soon as possible (1)
• Performance (1): the complexity of the CGI application may
mean decreased server performance (1)
Maximum 4 marks from any 2 of the above points.
(b)(i)If you were given
the responsibility of ensuring that everyone in the country
could not access any information about a particular topic (for example,The
X-Files)using the Internet, how would you go about it? Describe your
method,
and state whether you think it would be effective.[2 marks ]
Eliminate all sections of the Internet that included any reference
to The X-Files (1). This would be effective, but may eliminate other
useful sites (1).
(ii)If you were given
the responsibility of punishing anyone who accessed
information about the censored topic, how would you go about it?[1
mark ]
Monitor all the electronic traffic (email, WWW access etc.)of all
individuals (1).
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