Data Flow Diagram - DFD Levels, Symbols, Case Study, Tutorial, Example,

The Analysis Model is the first technical representation of a system. Analysis Modeling uses a combination of text and diagrams to represent software requirements (data, function, and behavior) in an understandable way. Building analysis models helps make it easier to uncover requirement inconsistencies and omissions. Two types of analysis modeling are commonly used:  (1) Structured Analysis (2) Object-Oriented Analysis Data Modeling uses Entity-Relationship Diagrams to define data objects, attributes, and relationships. Functional Modeling uses Data Flow Diagrams (DFD)   to show how data are transformed inside the system. Behavioral Modeling uses State Transition Diagrams to show the impact of events. Analysis work products must be reviewed for completeness, correctness, and consistency . Work Products of Analysis Modeling: Data object descriptions Entity relationship diagrams Data flow diagrams State transition diagrams Process specification and Control s

1.       Explain the relationship and differences between a module and a program. A program is a set of modules that work together to perform all the required functions. A module is a relatively small set of statements that carry out a single function.  2.       What is the purpose of the automation system boundary? How do you develop one? The automation system boundary defines which processes are going to be automated within the computer system, and which processes are part of the environment, or manual system. The system boundary, although needed for both structured and object-oriented development, needs to be defined explicitly for the structured approach. The object-oriented approach already has the system boundary defined in the use case diagram.  The automation system boundary is developed at the DFD fragment level or below, by defining which processes are manual and which are automated. The boundary line is a line between these two proce

A data flow diagram, like other models, has limitations. It is important to be aware of these limitations. Otherwise, it is easy to misunderstand data flow diagrams by making invalid inferences or by trying to read into a data flow diagram meaning which were not intended. (1) A data flow diagram does not show flow of control.   It is not a flowchart.   When alternative outputs may result from decisions within a transformation; a data flow diagram shows only the alternative outputs, not the decisions.  Only the incoming data flows appear as inputs to a transformation; if events or stimuli other than these inputs are necessary to activate the transformation, they are not shown. A transformation may be carried out many times while the system is in operation, but it is shown only once. A data flow diagram does not show details linking inputs and outputs within a transformation. It shows only all possible inputs and outputs for each transformation in

     A Data Flow Diagram is a network model of an information processing system. The arcs of the network represent data flows, and the nodes represent data stores, transforms, or selected elements of the environment. A Data Flow is a movement of information within the system or across the system boundary. A data flow which crosses the system boundary to enter the system is called a net system input  or simply System Input .  A data flow which crosses the boundary to leave the system is called a net system output or System Output . A Data Store is a time-delayed repository of information, where data is kept temporarily or permanently, avoid thinking of them in computer "file" terms, there are many quite different forms. A Process , or Transform , is a transformation that inputs one type of data and outputs a different type. It is a conversion of data from one form to another. A process cannot output data without getting some in, data