http://host/service/VirtualSystems will return all instances of VirtualSystem, HyperVSystem and VMWareSystem in a single query.

http://host/service/VirtualSystems/Model.HyperVSystem will restrict to instances of type "HyperVSystem" in schema "Model", and instances of any type that further specializes Model.HyperVSystem.

http://host/service/VirtualSystems/Model.VMWareSystem will similarly restrict to instances of Model.VMWareSystem and its specializations.

This is described in URL Conventions, section 4.9 Addressing Derived Types.

We don't have a way to only request instances of Model.VirtualSystem that are not also instances of a derived type.

If you are satisfied with this, please close the issue.

Thank you for the clarification. It is good if Spec is updated with such details.

What is the best way to limit "http://host/service/VirtualSystems" return only instance of VirtualSystem type but not derived types' instances. Can spec include query option?

I think the samples given by Ralf are derived from those in section 4.9 as he indicates, thus "the Spec" contains "such details" already

Is there a possibly less irritating sample you might offer for the follow-up question, where you only want the base type instances not including any derived type instances? I find myself caught in regarding these derived types as concrete types for the virtual type "VirtualSystem" ... and wonder if the intended latter query is a quest for NULLs so to say, those where another concrete type was not yet defined to put candidates in ... as I said, I am not sure where you are heading at ... otherwise $filter is a nice system query option ...

So having said that I second Ralf in asking to close the issue with no action.

Thank you.