Documentation and Data Flow Diagrams

Documentation

• The text explains documentation, which is a set of documents and models, often including narratives, data flow models, and flowcharts.
• Documentation details how, what, why, when, and where systems operate, encompassing input (data entry), process, storage, output, and controls.

Data Flow Diagrams

• A data flow diagram (DFD) visually presents how information flows within an organization.
• It is used to depict existing systems and design new ones.
• DFDs do not have a standardized creation method.

DFD Components

• DFDs are comprised of four primary elements:
  • Data Sources and Destinations: Represented as squares, these elements signify organizations or individuals involved in sending or receiving data for the implemented system.
  • Data Flows: Illustrated using arrows, these elements pinpoint the movement of data between sources, destinations, processes, and data stores.
  • Transformation Processes: Represented as circles, these elements symbolize the transformation of data within the system.
  • Data Stores: Visually depicted by two horizontal lines, these elements indicate temporary or permanent repositories of data within the system.

Data Dictionary

• The data dictionary provides comprehensive descriptions of data elements, data stores, and data flows within a system.

Context Diagram

• The highest level DFD, known as a context diagram, provides a concise summary-level view of the system. It depicts the complete system.
• It identifies the external entities serving as input sources and output destinations for the system.

DFD Guidelines for Creation

• To construct effective DFDs, follow these guidelines:
  • Understand the system: Thoroughly grasp the system's purpose and functionality.
  • Identify transformational processes: Recognize the processes that change data within the system.
  • Ignore certain aspects of the system: Avoid unnecessary details that can clutter the diagram.
  • Group transformational processes: Cluster related processes to enhance clarity.
  • Determine system boundaries: Clearly define the system's scope and limits.
  • Develop a context DFD: Start with the highest level DFD.
  • Identify data flows: Pinpoint all data movements within the system.
  • Group data flows: Combine similar flows to simplify the diagram.
  • Number each process: Assign distinct identifiers to processes for easy reference.
  • Label all DFD elements: Ensure all components are appropriately named.
  • Subdivide DFD: Break down large DFDs into smaller, more manageable sections as needed for clarity.

Flowcharts

• Flowcharts are analytical tools employed to represent an aspect of an information system in a clear, concise, and logical manner.
• Using standardized symbols, flowcharts visually delineate transaction processing procedures.
• Flowchart symbols can be categorized into four groups:
  • Input/Output Symbols: Illustrate the flow of information into and out of the system.
  • Processing Symbols: Represent actions or operations performed on data within the system.
  • Data Flow Symbols: Depict the movement of data between different components.
  • Terminal Symbols: Mark beginning and end points within the flowchart.