|| Supports tokens or username and password.
|| Allows the server to choose from a list of schemas, rather than
having one mandated by the client.
|| Allows the server to mark that the term being returned is the
same as the one requested after normalisation.
|| Allows the server to return any extensions it wants to.
|| Request a particular XPath from within records to be returned,
instead of the full record.
|| Request that the server return additional information regarding
the query, including suggested replacement terms, result sets or
the number of hits for sub-queries.