Plug-in software components called adapters connect a biometric unit to its underlying hardware and supply any functionality that may be missing from the sensor hardware. There are three types of adapters that you can create:
- A sensor adapter wraps a biometric device and provides a standard interface for configuring the sensor, capturing samples, and controlling the flow of biometric data to the processing engine.
- An engine adapter generates biometric templates from captured samples, matches samples to existing templates, and indexes templates.
- A storage adapter manages template databases.
Adapters can be loaded and unloaded at runtime. This enables the Windows Biometric Service to dynamically reconfigure a biometric unit by connecting it to a different set of adapters.
Finally, each of the sensor, engine, and storage adapter interfaces expose two methods, ControlUnit and ControlUnitPrivileged, that enable client applications to access custom adapter capabilities defined by the vendor. This allows the vendor to define an almost unlimited set of control operations for a device. Further, by choosing which function to implement, a vendor can choose to make some control operations available to non-privileged users while restricting other operations to privileged users.