wcf - customizing service document

I am new to WCF programming and its syndication classes etc. I am trying to produce a AtomPub service document programmatically when someone tries to access root address of my service. I am able to do that only to some extent using ServiceDocument, ResourceCollectionInfo, Workspace classes -

<service><app:workspace><a10:title type="text">Sample Repository</a10:title><app:collection href="http://some_url"><a10:title type="text">Root Collection</a10:title></app:collection>       </app:workspace></service>

However I would like to add some custom attributes and elements as can be seen below. Please notice the xmlns attributes, cmisra elements etc.

<service xmlns:cmis="http://docs.oasis-open.org/ns/cmis/core/200908/"xmlns:atom="http://www.w3.org/2005/Atom"xmlns:app="http://www.w3.org/2007/app"xmlns:cmisra="http://docs.oasis-open.org/ns/cmis/restatom/200908/"><workspace><atom:title>Sample Repository</atom:title>      <collection href="http://some_url"> <atom:title>Root Collection</atom:title> <cmisra:collectionType>root</cmisra:collectionType></collection> </workspace></service>

There is nothing much available on msdn website or elsewhere. Any inputs on how to achieve this would be appreciated.

Thanks!

Thanks.