Websites contain links, it in the nature of them. Links over time may become invalid, that is also in there nature. People who create links don't want to check manually if the links become invalid. This leads to the conclusion that there is a market for programs that can check links. The Programs do not only checks if a link is valid they also first need to acquire a list of links to check and they need to give feedback to the user.
This is what a link checker does
LinkChecker is not a crawler. It acquire a list of URL's with meta-data from a configured URL. The meta-data typically is information about the way to edit the URL [in MMBase terms this is the object number]
LinkChecker then processes the URL's in the list one by one. For each link LinkChecker checks the validity of the link by trying to access the URL. The result of the validity check consist of, a list of encountered errors, information about the time spent checking the link and information about the probability that the links was invalid. All this raw information is stored in 1 one file.
LinkChecker works with plugins to implement functionalilty