how changing URLs are handled

A wonderful feature of the R build system is that it checks URLs that are marked with the \url flag. This is also a bit of a pain, because URLs tend to move without notice, and to be down temporarily.

The way the developers check for broken links is to build R with e.g.

R CMD CHECK --as-cran oce_0.9-18.tar.gz

As of late 2015, here is the policy when a broken link is found.

• if direct access in a web browser works, assume this was a temporary problem and ignore it until the next time oce is built (typically within a day or two)
• if direct access fails, search the web to see if the URL has changed. If so, alter the documentation appropriately
• if direct access fails, and a new site for the page cannot be located, check the google cache for the last time the old link worked. Then edit the docs to mark the item with \code instead of \url, and note that the stated address had worked in the past but was found to fail on the date of the test. The idea of this is to give users a hint in case they want to search for themselves (e.g. by contacting the research group or company that seems to have hosted the site previously)