ABSTRACT
A data flow diagram is a logical model of the flow of data through a system that shows how the system’s boundaries, processes, and data entities are logically related. A data flow diagram is an excellent tool for summarizing and organizing detailed information about a system’s boundaries, processes, and data entities, providing the analyst with a logical map of the system. A data flow diagram is sometimes created in conjunction with an entity-relationship diagram or data normalization. Duplicate symbols are usually marked in some way; for example, source/destinations might be marked with a slash in the lower-left corner and data stores might be marked with an extra vertical line. In the data dictionary, each logical data structure must match a data flow or a data store, and each data element must appear at least once on the data flow diagram.
