More about entities, processes, files and data flows
Entities are used to represent people, places or things that are outside the system doing the information processing and for this reason are also known as external entities.
An entity acts simply as a source of and/or destination for data. Entities do not perform any information processing activities. Entities are generally labelled using a noun.
Processes usually represent a group of information processing activities.
Information processing activities include: capturing data on source documents; sorting data; and adding records to a file. Sending or receiving data and operational activities are generally not classified as information processing activities.
How information processing activities are grouped into processes and labelled requires judgement and will vary from person to person. The process label reflects the general nature of the processing completed by the entire group of activities rather than a specific information processing activity within the group. Processes represent actions being performed, and thus their labels should begin with a verb.
Files (or data stores) hold data that is used or created by an information processing activity.
Accounting records such as ledgers, sub-ledgers and transaction logs are examples of files. ALL files should be labelled and the name should reflect the data that is being stored.
Data flows indicate the direction of the flow of data between components of the DFD.
The names used to label data flows (for those data flows that need to be named) are generally nouns and should describe the data flowing between DFD components. Each data flow label should be unique unless the identical data is sent to or received from more than one DFD component.