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    bool write(char *name, char *value, ControlDestiantionControlDestination destination, ...)

Where name is the name of the value to write, and value is the string representation of the value to write. The destination argument controls where the request will be routed and uses additional argument to qualify that routing.

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    int operation(char *operation, int paramCount, char *names[], char *parameters[], ControlDestination destination, ...)

Where name is the operation is the name of the operation to be executed, and paramCount is the number of parameters to be passed to that operation names is an array of the parameter names and parameters is an array of string values that are the parameters themselves. The length of the names and parameters arrays should both be paramCount. The destination argument controls where the request will be routed and uses additional argument to qualify that routing.

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    write(“test”, “value”, DestAssetSource, “Transformer1Temperature”);

Callback Initialisation

A north plugin that implements control flow must signal to the north service that is loading the plugin that it implements the control flow and provide an entry point that will be used by the north service to pass the callback pointers to the north plugin. Note, north plugins that are run by a north task rather than as a service will not be able to use the control flow.

A north task signals that it supports the control flow by adding the flag SP_CONTROL to the flags field of the information structure that the plugin_info call returns.

When the north service detects that the plugin supports the control flow it will make a call to pass the callback function pointers to the plugin. This call is made after the call to plugin_init has completed.

    void plugin_register(PLUGIN_HANDLE handle, bool ( *write)(char *name, char value, ControlDestination destination, ...), 
                                     int (* operation)(char *operation, int paramCount, char *parameters[], ControlDestination destination, ...))

The plugin should retain these two function pointers for use when it wishes to invoke control operations.

Security

The advent of control increases the need for strict security mechanisms within the system. However end to end security can not be achieved by simply adopting the security mechanism of the control message producer with that of the consumer, they may have different security models and a single producer may be communicating with multiple consumers, each with a different security model.

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