FME Workbench permits multiple data streams, each of which passes through its own set of transformers.
A key concept in FME is the ability to create multiple processing streams within a workflow or to bring several streams together into one.
Similar terms to 'stream' are 'flows,' 'pipes,' or 'pipelines.' Creating Multiple Streams
Splitting data occurs with any transformer with multiple output ports (a Tester transformer is a good illustration of this) but can also be achieved by simply making multiple connections out of a single output port.
The difference is that when using multiple ports the data is being split amongst the different streams.
However, when using multiple connections from a single port, the data is being duplicated rather than being split. In effect it creates a set of data for each connection.
Here, 50 road features are being read but, because there are multiple connections from the feature type, multiple copies of the data are being created.
Multiple streams are useful when a user needs to process the same data, but in a number of different ways.
When multiple streams are brought into the same input port no merging takes place. The data is simply accumulated into a single stream. This is often called a "Union".
Here, three streams of 50 features each, converge upon a single AreaCalculator:INPUT port.
Notice how no merging has taken place; the data simply accumulates into 150 output features.
To carry out actual merging of data requires a specific transformer such as the FeatureMerger.