A system which feeds information into a second system, platform, or application, usually in order to provide a focal point for managing a certain type of information.
A Product Information Management (PIM) system would get raw data from various Upstream Systems focusing on data collection or product development. That data would be used, processed and analyzed for the purposes of product information. Then, the PIM system in turn would become an upstream system supplying that product information to systems with a different focus, such as content management systems. Any change to how upstream systems operate or to their data will have an effect on any system that receives information from them.
Path Dependence, Downstream