REST start a Workflow with Input-Parameter VC:VirtualMaschine

Hey everybody,

i'm trying to start a workflow via a REST-POST-Call to Start a Virtual Maschine.

I use the HTTP ContentType "text/XML" and call via

"https://{vmhost}:{port}/vco/api/workflows/{workflowID}/executions/ 

and send the following httpBody:

<execution-context xmlns="http://www.vmware.com/vco">

<parameters>

<parameter name="vm" type="VC:VirtualMaschine">

<VC:VirtualMaschine>vm04711</VC:VirtualMaschine>

</parameter>

</parameters>

</execution-context> 

but there are come back a Error-Message

"REST: HTTP POST request failed with error 400 (Bad Request)"

I don't know, if there parameters are in the httpBody are correct. The Input-Parameter in the Workflow has the Name "vm"  with the type "VC:VirtualMaschine".

In the Doc http://pubs.vmware.com/orchestrator-70/topic/com.vmware.ICbase/PDF/vrealize-orchestrator-70-develop-web-services-guide.p…

there is an example with string but with an VC:VirtualMaschine-Type, i don't know who are the Syntax is.

Could someone help me - thanks a lot

greetings