DFD COMPONENTS

SOURCE

• Performs processes excluded from the scope of the system being modeled
• Sometimes referred to as Agents

TYPE OF SOURCES

• Internal sources
• Office, department, employee within the company
• External sources
• Office, department, employee outside the company
• Another system
• Include only if the modeled system communicates directly with the programs of the other system

NAMING / LOCATING SOURCES

• Name should be based on the title of the person or entity
• Register, Supplier, Marketing, IS
• Should be located on the perimeter of the page
• May be duplicated sparingly to avoid crossing lines

DATA FLOWS

• The input of data to a process
• Represent the minimum essential data the dependence or coupling between processes

DATA FLOW GUIDELINES

• Must begin at a source, must end at a sink or at a source
• should be given unique names
• name should be some identifying noun
• order, payment, complaint

DATA STORES

• A repository for data that are temporarily or permanently recorded within the system
• An "inventory" of data
• Common link between data and process models 
• Commonly referred ti as sink