IDataQuery - Making more powerful queries

Hello,

Is there a way to make queries targeting Work Items using the RTC API's IDataQuery without using any internal APIs (i.e. WorkItemQueryModel)?

Also, is there a way to select and filter results by custom attributes
of type WorkItem and WorkItemList?

IDataQuery provides much more power than the IQueryClient, and us and our clients are used to the ClearQuest queries, so it is very important being able to use IDataQuery to query Work Items.

Thanks in advance,
Claudio Neves