The Relationship among System Flowchart, Data Flowchart and Data Dictionary

System flow chart is a traditional tool to describe the physical model of the system. Its basic idea is to describe every component (program, file, database, table, manual process, etc. ) in the system in the form of a black box with graphical symbols, and to express the information flow between components.

Data flow diagram (DFD) is a main tool that can fully describe the logical model of information system. It can fully reflect the flow, processing and storage of information in the system with fewer symbols. A data flow chart represents the direction of operation or data.

Data dictionary refers to the definition and description of data items, data structures, data streams, data storage, processing logic and external entities. Its purpose is to describe each element in the data flow diagram in detail. A data dictionary is a directory that users can access to record database and application source data. Active data dictionary refers to a data dictionary whose contents can be automatically updated by DBMS when the structure of database or application is modified. A passive data dictionary refers to a data dictionary whose contents must be updated manually when it is modified.