Hello, Thanks for your answers! Well, the code itself is valid, but some IDEs (in my case netbeans) use them to enable smart code completion and other features for those tags. The problem is that the URI it needs (http://shale.apache.org/core) is a 404 and I get no help from netbeans. Also, I've found a few other broken links on the website that would be nice to be fixed:
Only http://wiki.apache.org/shale/ShaleValidation references two broken ones. I'll try Richard's tip and report any results. Many thanks, Cristi