...
                        var options =  {
                          get : function() {
                             return new Variant({...});
                          },
                          set : function(variant) {
                             // store the variant somewhere
                             return StatusCodes.Good;
                          }
                       };
                       ...
                       engine.bindVariable(nodeId,options):
                       ...
                    

Variation 2:

This variation can be used when the user wants to specify a specific '''sourceTimestamp''' associated with the current value of the UAVariable.

The provided timestamped_get function should return an object with three properties:

• value: containing the variant value or a error StatusCode,
• sourceTimestamp
• sourcePicoseconds

...
                    var myDataValue = new DataValue({
                      value: {dataType: DataType.Double , value: 10.0},
                      sourceTimestamp : new Date(),
                      sourcePicoseconds: 0
                    });
                    ...
                    var options =  {
                      timestamped_get : function() { return myDataValue;  }
                    };
                    ...
                    engine.bindVariable(nodeId,options):
                    ...
                    // record a new value
                    myDataValue.value.value = 5.0;
                    myDataValue.sourceTimestamp = new Date();
                    ...
                    

Variation 3:

This variation can be used when the value associated with the variables requires a asynchronous function call to be extracted. In this case, the user should provide an async method refreshFunc.

The refreshFunc shall do whatever is necessary to fetch the most up to date version of the variable value, and call the callback function when the data is ready.

The callback function follow the standard callback function signature:

• the first argument shall be null or Error, depending of the outcome of the fetch operation,
• the second argument shall be a DataValue with the new UAVariable Value, a StatusCode, and time stamps.

Optionally, it is possible to pass a sourceTimestamp and a sourcePicoseconds value as a third and fourth arguments of the callback. When sourceTimestamp and sourcePicoseconds are missing, the system will set their default value to the current time..

...
                    var options =  {
                       refreshFunc : function(callback) {
                         ... do_some_async_stuff_to_get_the_new_variable_value
                         var dataValue = new DataValue({
                             value: new Variant({...}),
                             statusCode: StatusCodes.Good,
                             sourceTimestamp: new Date()
                         });
                         callback(null,dataValue);
                       }
                    };
                    ...
                    variable.bindVariable(nodeId,options):
                    ...
                    

Providing write access to the underlying value

Variation1 - provide a simple synchronous set function

Notes

to do : explain return StatusCodes.GoodCompletesAsynchronously;