[Laurens]

The key to link rewriting is using so-called "marked subexpressions".

The regular expression for matching article URLs is fairly straightforward:

http://.*\.?opendemocracy\.net/.*/article\.jsp\?id=\d*.*articleId=\d*.*

What you want to do is extract certains parts of a matching URL to construct a handheld-friendly URL. You can do this by marking these parts as subexpressions by putting them between parentheses:

(http://.*\.?opendemocracy\.net)/.*/article\.jsp\?id=(\d*).*articleId=(\d*).*

Each subexpression in a matching link is assigned a number. You have to put a dollar sign in front of them when rewriting the link. In this case there are three submatches: $1, $2 and $3.

Once you have understand this and have this working, rewriting the link becomes very simple:

$1/articles/ViewPopUpArticle.jsp?id=$2&articleId=$3

There's far more to regexp, but you don't need to know everything to use link rewriting.