Using the ExternalDataExchange Attribute
Although we have an interface, IMVDataService, we haven’t yet done enough to provide this interface to WF and have WF actually use the interface for data communications. To do that, we need to add the ExternalDataExchange attribute.
Later we’ll also add attributes associated with correlation. We’ll look at correlation attributes in greater detail in Chapter 17, but for now, just think of correlation as a way to keep different data requests sorted out. I mention it here because your data communication interface is where you specify correlated data values.
The ExternalDataExchange attribute is simply a marker ...