Which name of the data flow is invalid on a physical data flow diagram?

In a physical data flow diagram, an invalid name for a data flow might be something vague or non-descriptive, such as "Data" or "Information." Data flows should have clear and specific names that indicate the type of data being transferred, such as "Customer Order Data" or "Invoice Information." Using ambiguous names can lead to confusion and misinterpretation of the system's operations.