E. History

LinkController was originally inspired by MOMspider and having the MOMspider code available was very useful when starting the creation of this kit, but, it shares almost no code with MOMspider, other than what has comes to it from the LibWWW-Perl library.

Philosophically, the MOMspider heritage is obvious in the wish to handle big jobs efficiently. In the working practice there are far more differences than similarities, partly caused by Perl language changes.

I decided to completely separate the exploration of the local infostructure, looking for links to be checked, from the actual checking process. This means that checking can be spread over a large number of days and still run efficiently.

The basic aim of this link checking kit is to be able to efficiently handle any size of link checking job. At the bottom end we have checking new pages as they are written. Here we want to use information from previous checks to avoid having to check all of each page every time. At the other end we have massive info structures (sites) which deal in many thousands of links and could not possibly all be checked in one day. For this latter case the aim is to be able to efficiently spread the link checking load into all available low usage periods.

My primary aim in writing this was not to write very efficient code for the small scale case (takes minimum time to do everything), but rather code which would scale well. If your system can check 1000 links in two days, it will hopefully be able to check almost 7000 links in two weeks. I'm trying to make sure all data structures which grow with the number of links are kept on disk.

E.1 Acknowledgements

People and or institutions who helped

E.1 Acknowledgements

Although I wrote this system by myself, this would not have been nearly as easy and almost certainly wouldn't have ever been finished without the help of the following people and organisations.

Esoterica Internet Portugal
IPPT PAN Poland
The Tardis Project
Other Free Software Authors

Esoterica Internet Portugal

Esoterica provided me with full access to the Internet in Portugal and use of their computers for free which allowed me to keep up on both this software and the Linux Access HOWTO. In particular I'd like to thank all of the members of staff who helped me very much. These people include Mario Francisco Valente (the instigator of Mini Linux) who first agreed to me using their kit, set me up to use their machines, and along with Luis Sequeira provided a sounding board for some ideas. Luis also provided the odd lift home in the evening. Also Martim de Magalhaes Pereira and Mr Mendes. See them all on

http://www.esoterica.pt/esoterica/quemsomos.html

For more about esoterica (Internet Services in Portugal) see:

http://www.esoterica.pt/esoterica/

These pages are in Portugese(3) of course.

IPPT PAN Poland

Thanks go to IPPT PAN (part of PAN - Polska Akademia Naukowa) in Poland and in particular Piotr Pogorzelski who allowed me use of facilities for testing this software, provided a willing victim for having his web pages tested and made a number of suggestions which have been incorporated into the software.

The Tardis Project

Supported by the Computing Science department of the University of Edinburgh, the Tardis project provides an experimental framework in which students, former students and other related people to do their own work on fully Internet connected Unix and Linux hosts.

The use of the facilities of the Tardis Project has made it much easier for me to develop software like this. In particular, the large amount of disk space the administrators have allow me to use is very useful.

Other Free Software Authors

It is through the software provided by the Free Software Foundation (such as the gcc C compiler, Emacs, the file utilities), the authors of the various packages which make up a working Linux System (Linux by Linus Torvalds, Alan Cox, etc.... filesystems and support by Theodore Tytso, Stefan Tweedie etc.. Linux-Libc by HJ Lu, based on GNU glibc from the FSF.. the list is indefinite) and the authors of Perl and its modules, especially Gisle Aas and Martijn Kostler for LibWWW-Perl that I was able to set this up.

I'd particularly like to thank Tim Goodwin the author of the Perl CDB module who made and accepted a number of alterations to that, at my request. These alterations made this package simpler to write and easier to maintain.

The Free Software Foundation web pages are at

http://www.gnu.ai.mit.edu/