Networked Media Open Specifications

Components of the architecture

←Definitions · Index↑ · Control Model→


NCA is based on two interrelated models:

Classes, objects, and APIs

In NCA, each control object has its own control API. The signature of each object’s API is completely defined by the class of which it is an instance. The complete API of a Device is exactly equal to the union of the APIs of all the objects it contains.

Thus, if a Controller knows all the objects in a Device, and if it knows the definitions of the classes of which those objects are instances, then it knows the Device’s complete API.

In some cases, Controllers will have been custom-built for Devices they control, and will therefore have the required object and class information a priori. However, NCA provides rich mechanisms for controllers to acquire such information from the devices themselves.

In reading this specification, it is important to remember that NCA is concerned only with defining Device control and monitoring APIs, not with internal implementation structures that lie behind those APIs in NCA-compliant products.


A Controller needs a control protocol to access Device control APIs. NCA’s Control Model defines APIs abstractly, leaving their realizations in protocols to separate specifications.

All NCA compliant protocols implement the Control Model as described in Control Model and defined in MS-05-02.

←Definitions · Index↑ · Control Model→