Data flow diagram

data flow diagram ( DFD ) is a graphical representation of the “flow” of data through an information system , modeling its process aspects. A DFD is often used as a preliminary step to create an overview of the system without going into great detail, which can later be elaborated. [2] DFDs can also be used for the visualization of data processing (structured design). Citation needed ]

A DFD shows what kind of information will be input to and output from the system, how the data will advance through the system, and where the data will be stored. It does not show information about process timing or whether processes will operate in sequence or in parallel, in Unlike traditional structured flowchart qui Focuses on control flow, gold UML activity diagram workflow, qui present Both control and data flows as a unified model. Citation needed ]

History

In the 1970s, Larry Constantine , the original developer of structured design, proposed data flow diagrams as a practical technique based on Martin and Estrin’s “Data Flow Graph” model of computation. [3]

Data flow diagrams (DFD) has become a popular way to visualize the major steps and data involved in software system processes. DFDs were used to describe the flow of a process . DFDs were useful to document the major data flows or to explore a new high-level design in terms of data flow. [4]

Theory

Data flow diagrams are also known as bubble charts. [5] DFD is a designing tool used in the top-down approach to Systems Design. This context-level DFD is next “exploded”, to produce a Level 1 DFD that shows some of the detail of the system being modeled. The Level 1 DFD shows how the system is divided into sub-systems (processes), each of which deals with one or more components of the system. whole. It also identifies internal data stores that should be present in order for the system to do its job, and shows the flow of data between the various parts of the system. Citation needed ]

Data flow diagrams are one of the three essential perspectives of the structured-systems analysis and design method SSADM . The sponsor of a project and the end users will be briefed and consulted throughout all stages of a system’s evolution. With a data flow diagram, users are able to visualize how the system will operate, what the system will accomplish, and how the system will be implemented. The old system’s data flow diagrams can be drawn up and compared with the new system’s data flow diagrams to draw comparisons to implement a more efficient system. Data flow diagrams can be used to provide the end user with a physical idea of ​​where the data they input ultimately has an effect on the structure of the whole system from order to dispatch to report. How can a system be developed? Citation needed ]

In the course of Developing a set of leveled data flow diagrams the analyst / designer is forced to address how the system May be decomposed into component sub-systems, and to Identify the transaction data in the data model . Citation needed ]

Data flow diagrams can be used in both the Analysis and Design phases of the SDLC . Citation needed ]

There are different notations to draw data flow diagrams (Yourdon & Coad and Gane & Sarson [6] ), defining different representations for processes, data stores, data flow, and external entities. [7]

Physical vs. Logical DFD

A logical DFD captures the data flows that are necessary for a system to operate. It describes the processes that are undertaken, the data required and produced by each process, and the stores needed to hold the data. On the other hand, a physical DFD shows how the system is actually implemented, either at the moment (Current Physical DFD), or how the designer intends it to be in the future (Required Physical DFD). Thus, a Physical DFD may be used to describe the set of data items that appear on each piece of paper that move around an office, and the fact that a particular set of pieces of paper are stored together in a filing cabinet. It is quite possible, That a Physical DFD will include references to data That are duplicated, or redundant, and que la datastores, if Implemented as a set of database tables, Would constitute an un-normalized (or de-normalized) relational database. In contrast, a logical DFD attempts to capture the data flows of a system in a form that does neither redundancy nor duplication. Citation needed ]

See also

  • Activity diagram
  • Business Process Model and Notation
  • Control flow diagram
  • Data island
  • dataflow
  • Directed acyclic graph
  • Drakon-chart
  • Functional flow block diagram
  • Function model
  • IDEF0
  • Pipeline
  • Structured Analysis and Technical Design
  • Structure chart
  • System context diagram
  • Value stream mapping
  • workflow

References

  1. Jump up^ John Azzolini (2000). Introduction to Systems Engineering Practices. July 2001.
  2. Jump up^ Bruza, PD, Van der Weide,[ citation needed ]Th. P., “The Semantics of Data Flow Diagrams”, University of Nijmegen, 1993.
  3. Jump up^ W. Stevens, G. Myers, L. Constantine,”Structured Design”, IBM Systems Journal, 13 (2), 115-139, 1974.
  4. Jump up^ Craig Larman, Applying UML and Patterns, Pearson Education,ISBN 978-81-7758-979-5
  5. Jump up^ Introduced by Clive Finkelstein in Australia, CACI in the UK, and later writers such as James Martin
  6. Jump up^ Chris GaneandTrish Sarson. Structured Systems Analysis: Tools and Techniques. McDonnell Douglas Systems Integration Company, 1977
  7. Jump up^ How to draw Data Flow Diagrams

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