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WDF Object Model

User Mode Objects

UMDF objects are based on the component object model (COM). The UMDF uses a small subset of COM for query-interface and reference counting features. In the UMDF driver, both the driver and the framework implement and expose the COM-style interface. Handles are not required because the interfaces are abstract base classes and thus identify the object.

The UMDF defines fewer objects than the KMDF because User Mode Driver cannot directly access hardware and therefore does not perform direct memory access (DMA) or handle interrupts. The following is a list of interfaces that expose the UMDF object types:

Object Interface Name



Defines the base WDF object type


Represents the driver object


Represents a device object


Represents a file object


Represents a queue of I/O requests


Describes an I/O request


Represents the driver that is the target of an I/O request


Provides access to an area of memory

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