[xwiki-users] How do I write a correct XWQL statement?

I tried to execute a Query and saw an error below. Caused by: org.xwiki.query.QueryException: Exception while translating [select srv from IN (doc.getObjects("Private.Network Services")) srv order by srv.port] XWQL query to the [hql] language. Query statement = [select srv from IN (doc.getObjects("Private.Network Services")) srv order by srv.port] Although I read JPQL documents, I couldn't come out with an answer. Does anybody know how to write a correct XWQL statement?