How can this be achieved?

DRAG DROP
There is a WCF (Windows Communication Foundation) service PassGuideService.
PassGuideService uses POX (plain-old xML).
Only POX, JSON, or ATOM formats must be used by /catalog.svcfitems operation when it
responds. The usage of these same URL must be enforced whatever the result type.
The response format must be determined through the Accepts HTTP header.
How can this be achieved?