©1996-2017 Roedy Green of Canadian Mind Products
This essay does not describe an existing computer program, just one that should exist. This essay is about a suggested student project in
Java programming. This essay gives a rough overview of how it might work. I have no source, object, specifications, file layouts or anything
else useful to implementing this project. Everything I have prepared to help you is right here.
This project outline is not like the artificial, tidy little problems you are spoon-fed in school, when all the facts you need are included, nothing extraneous is mentioned, the answer is
fully specified, along with hints to nudge you toward a single expected canonical solution. This project is much more like the real world of messy problems where it is up to you to fully the
define the end point, or a series of ever more difficult versions of this project and research the information yourself to solve them.
Everything I have to say to help you with this project is written below. I am not prepared to help you implement it; or give you any additional materials. I have too many
other projects of my own.
Though I am a programmer by profession, I don’t do people’s homework for them. That just robs them of an education.
You have my full permission to implement this project in any way you please and to keep all the profits from your endeavour.
Please do not email me about this project without reading the disclaimer above.
This project is not so pressing now that the WebRing people are finally getting their
act together and making the system user-friendly.
WebRings are groups of like-minded websites. You can browse from site to site in a
circle by clicking a button. You can go forward or back. You can jump to a random site.
You can see a list of all the sites and jump directly to any one of them. Yahoo organises such rings for free. For
details on how they work, see WebRing
in the Java glossary.
There is a central controller CGI (Common Gateway Interface) app running on a server that
figures out where to jump to next when a given button is pressed. When the user hits
next, prev, random or list, (usually on a custom
CGI graphic map or
circle. There are three major problems with WebRings as they currently exist:
Your job is to write a servlet that runs a collection of WebRings, sending browsers
onto the next link. You need to find low-cost, solutions to the above three problems. You
want the user interface extremely simple so that almost anyone could set up a WebRing
server and run it with little time investment.
- The HTML (Hypertext Markup Language) for linking at
each site is not properly verified. The target URL (Uniform Resource Locator)
should be precisely the spot on the page where the link control to
the next site is, with #NAME tag. With the current unverified schemes, you may land
at somebody’s home page and have to dig through his entire site to find the
next link. (There might not even be one, if the site’s owner made an
or dropped out of the ring without informing the Ring Master.) You may land on a page
with links to 20 other WebRings on it. You have to find the link for the WebRing you
are interested in. We need to automatically verify (and periodically
reverify) that the HTML
target URL and the
link control HTML buttons at that target are properly configured. You
need a precise target URL
of the form:
http://www.MySite.com/ringpage.html#SuperRing$209078$7752$13413where SuperRing is the ring software scheme,
20978 is the server id, 7752
is the ring id and 13413 is the site id. IDs are small
integers evenly divisible by 17 (which acts as a simple checksum, yet allows ids
(after division by 17) to directly index tables).
- Like the old serial Christmas tree lights, if any link in the chain goes down, the
entire ring is broken. The central site needs to keep tabs on all the sites and remove
ones (temporarily and eventually permanently) that do not respond. Some rings have a
button to bypass the next site to help get around the problem. However, that
won’t help unless the user knows to try that. It also requires there not be two
dead sites in a row. Note that current schemes don’t directly send the user to
the next site in the ring. They always send him to the ring hub for redirection.
However, if there is no working link back to the ring hub, the chain is broken.
- Users periodically reorganise their websites. This means that rings may move from
page to page without officially informing the central site of the new location. These
links can be made self-healing.
On the other extreme, you could insert a perfectly standard
piece of HTML in a web page, not customised in any way. It looks up
the web page URL to see what rings are registered there. You could put
that link on every web page, then manage centrally at the ring hub which rings you
want to appear on which pages. You could have a ring appear more than once on your
website. You could see centrally which links are valid. What you want to avoid is the
problem of needing to install new gobbledegook nav bar codes every time a web page is
renamed or split.
- Automatically. At night the central site chases rings looking for broken links.
When it finds one, it searches that website for the moved reference. If it
can’t find it, it takes the website offline.
- Semi-Automatically. When you click the icon it could send its location to the
central site. If it has changed and if the old page no longer contains the link,
the central information could be automatically updated. If the old page is still
valid, the central system could generate an email asking for clarification. It
might be quite reasonable to have several references to the same ring on a website,
though, of course, there has to be one master link where incoming visitors are
There are four levels of organisation:
Individual Site Master
One for each site on a ring. A site may be on several
rings. They may be on rings using different software schemes.
Decides the ring’s charter and who should be allowed on
the ring. Monitors that members are conforming to the charter. Handles technical
support for the sites on the ring. Maintain the master list of sites on the ring and
a home page for the ring. Composes a logo for the ring.
Runs a server than services many rings. Handles technical
support from the Ring Masters, but not from individuals or individual Site Masters.
Maintains a master list of rings handled by the server and a home page for the
server’s ring service.
Global Directory Master
Much the way DNS (Domain Name Service)
works, the server sites automatically share their directories of rings to form a
master directory of rings. This way each site has a copy of the global directory of
all rings on the Internet (ideally even including ones not using your software).
Alternatively, server sites may not keep a local copy of the complete list, but
instead maintain a link to where a global copy can be obtained. End users of the
system are, for the most part, unaware of these organisation levels. They can find a
list of sites on a ring, a list of other WebRings on the server or a master list of
all the WebRings (categorised and keyword searchable) just by clicking buttons.
- You need to use a program like
HTML Validator to verify any fragments asked to be included in other
people’s pages. It is highly annoying to be given bad html code to be inserted
in your web page, even if it works in IE (Internet Explorer).
is probably best to use it to generate complex displays from a tiny piece of embedded
- To make rings more accessible, even the ringmaster should not need to know
should be able to generate the necessary embedded HTML
master template by answering multiple choice questions.
- The ringmaster should have ways of generating individual or bulk Emails to various
subsets of the ring members. Members should have a way of sending emails to the
ringmaster. People visiting the sites should be able, using the ring, to send mail to
the owner of the site, or to the ringmaster.
- If the ringmaster does not log in for a month, the system automatically polls the
existing ring members to assign a new ringmaster.
- The ringmaster should have the option of requesting an automatic email any time
someone asks to join the ring or changes their description.
- The ringmaster should be given the power to edit the URLs (Uniform Resource Locators)
or site descriptions.
- Since most people can’t edit HTML,
think about how you could have a server system that did not require any embedded
HTML, just a
link to a page or virtual page on the ring server that contained all the rings that
site owned. There could be a link back to the site for each ring.
- Become a ringmaster on Yahoo and learn what the practical problems are and the
deficiencies with the Yahoo system.
- Site owners are usually both unwilling and incapable of inserting nav bars or ring
icons into their HTML. Perhaps this process could be semi-automated. Perhaps
the ring master could do it and email the corrected page back for uploading. You want
tools so the ringmaster can do this quickly.