We need to be able to describe systems to assist with development, to assist with use, and to assist with maintenance. To that end, diagrams provide a concise, semi-formal way of describing a system. Data flow diagrams are an important tool in the development of information systems. Below are descriptions of Context diagrams, Physical Data Flow Diagrams, and Logical Data Flow Diagrams. Please fill in the missing words in the spaces provided. 

 

Context Diagrams are top-level, least-detailed diagrams of an information system. They provide the system's context in relation to the data flows ____ and _____ of the system and _____ and _____ of the external entities.

Physical Data Flow Diagrams describe graphically the system's internal and external entities (things), and the data flows into and out of these entities. Physical Data Flow Diagrams depict _____, _____, and by _____ a system's processes are accomplished, however they do not indicate _____ was done.

Logical Data Flow Diagrams represent the system's processes, and the flows of data into and out of those processes. _____ tasks are being accomplished is the domain of the logical data flow diagram and these tasks remain relatively ________.