"david.lloyd(a)jboss.com" wrote : I see - so I can attach any kind of MetaData, so long as it implements MetaData? Does the MDR (or any other project) define a convention for this? | Look at MutableMetaData class. MetaData == any object; We just have annotation notion for ease of use. Another useful class is MetaDataStack, so you can get to MetaData instance from anywhere - via classic thread local hack. :-) "david.lloyd(a)jboss.com" wrote : | What is the lifespan of something I put in there? | It's up to you. We don't have any magic cleaning. We only do a cleanup at undeploy - see your last question. "david.lloyd(a)jboss.com" wrote : | Can I cause leaks by attaching stuff? | Sure. At the end, metadata is nothing more then sophisticated Map. It's the api that makes it useful. "david.lloyd(a)jboss.com" wrote : | Is it removed on undeploy somehow? | Yes. In DeployersImpl we call DeploymentContext::cleanup, which cleans up the scope matching metadata retrievals. View the original post : http://www.jboss.org/index.html?module=bb&op=viewtopic&p=4209390#... Reply to the post : http://www.jboss.org/index.html?module=bb&op=posting&mode=reply&a...