3.1 Data Flow

• Data flow diagrams are used to graphically represent the flow of data in a business information system
• Data flow diagram


  Describes the processes that are involved in a system to transfer data from the input to the file storage and reports generation
• Visual representation of data flow diagram


  Good communication tool between User and System designer
• DFD Symbols


  • Process
  • Data Flow
  • Data Store
  • External Entity
• Process


  • Receives input data and produces output with a different content or form
  • Has a name that identifies the function it performs (verb + singular noun)
• Data Flow


  A path for data to move from one part of the information system to another
• Every process must have at least one data-flow entering and one data-flow exiting
• Data Store


  • Used to represent a situation when the system must retain data because one or more processes need to use the stored data in a later time
  • Must have at least one input data-flow and at least one output data-flow
• External Entity


  • A person, department, outside organization, or other information system that provides data to the system or receives outputs from the system
  • Does not process data
• Top-Down Decomposition Techniques


  1. Display the targeted system as a single process, then show more detail until all processes are functional primitives

  2. Balancing DFD - inputs and outputs must be conserved between levels of DFDs
• Guidelines for Developing Data-Flow Diagram

  • Context Diagram - Level 0
  • Unique Name for Levels
  • No Cross Line in DFD
  • Right Complexity for Human Mind - 7 + / - 2 Symbols
  • Numbering Convention
  • Context-Level Diagram
  • Level 1 DFD
  • Level 2 DFD
• What is the study of Materials Science focused on?

  Relationships between processing, structure, and properties
• What does Materials Engineering involve?

  Designing material structures for specific properties
• What are the four important components of Materials Science and Engineering?

  Processing, Structure, Properties, Performance
• Why must applied scientists or engineers study materials?

  To make informed material choices
• What are some properties to consider when selecting materials?

  Strength, ductility, malleability, cost
• What is the significance of environmental conditions in material selection?

  They affect material performance and durability
• What are the classifications of materials?

  Metals, Ceramics, Polymers, Semiconductors, Composites, Biomaterials
• What are the characteristics of metals?

  Good conductors, strong, deformable
• What defines ceramics?

  Compounds between metallic and nonmetallic elements
• What are composites made of?

  Combinations of two or more different materials
• What are polymers primarily composed of?

  Organic compounds based on carbon and hydrogen
• What is the role of semiconductors?

  Intermediate between conductors and insulators
• What are biomaterials used for?

  Implanting into the human body for replacements
• What are the types of primary atomic bonds?

  Metallic, Covalent, Ionic bonds
• How do metallic bonds function?

  Valence electrons form a "sea" around atoms
• What characterizes covalent bonds?

  Sharing of valence electrons among atoms
• What happens in ionic bonding?

  Metallic elements donate electrons to non-metallic elements
• What distinguishes crystalline materials from amorphous materials?

  Crystalline materials have a regular atomic arrangement
• What is a unit cell in crystallography?

  Smallest repeatable entity representing a crystal structure
• What is the coordination number in a crystal structure?

  Number of atoms touching a particular atom
• What is the atomic packing factor (APF)?

  Fraction of space occupied by atoms in a structure
• What is allotropy?

  Phenomenon where elemental solids have multiple structures
• What are point defects in materials?

  Localized disruptions in atomic arrangements
• What is a vacancy in point defects?

  Missing atom at a normally occupied lattice point
• What are substitutional impurities?

  Host atom replaced by an impurity atom
• How do dislocations affect materials?

  They misalign atoms, affecting strength and ductility
• What are grain boundaries?

  Surfaces separating individual grains in a material
• What are the mechanical properties of materials?

  • Strength
  • Ductility
  • Hardness
  • Toughness
• What are the thermal properties of materials?

  • Thermal conductivity
  • Thermal expansion
  • Heat capacity