The pipeline is the general term used to refer to the data structure in which input and output values are maintained for a flow service. It allows services in the flow to share data.

The pipeline starts with the input to the flow service and collects inputs and outputs from subsequent services in the flow. When a service in the flow executes, it has access to all data in the pipeline at that point.

When you build a flow service, you use Designer to specify how information in the pipeline is mapped to and from services in the flow.