Low level design.md

Low-level design:

Objects and Classes:

• Objects:
  • A real world element in object oriented environment, that may have physical or conceptual existence.
• Classes:
  • Blueprint or description of objects, that can be created from it.

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Software development process:

• Problem solving process:
  1. Requirements Analysis
  2. Design
  3. Implementation
  4. Delivery

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UML Diagram:

• The Unified Modeling Language (UML) is a standard graphical language for modeling object-oriented software.

• As UML is a graphical language, it supports two types of diagrams which can be classified as:

  • Structural:
    • The structural Diagrams are used to create a static model of the software.
    • That is it gives an idea, what all components build up the system.
  • Behavioral:
    • The Behavioral Diagrams are used to create a dynamic model of the software.
    • It tells how the different components or modules interact with each other.

• Some of the structural and behavioral diagrams supported by UML are:

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Class Diagram and Object Diagram:

• Class diagram:

  • A class diagram in the Unified Modeling Language (UML) is a type of structural diagram that describes the structure of a system by showing the System's Classes, their Attributes, Operations (or methods), and the relationships among objects.
  • In a class diagram a class is represented with the help of a rectangular box having three partitions:
    • The first partition contains the class name,
    • The second partition contains all the attributes of the class.
    • The third partition contains all the functionalities of the class.

• Relationships:

  • The connection between the two classes in a class diagram is called Relationship. A class may be involved in one or more relationships with other classes.

  1. Association:

     • It shows that one class is associated with other classes.
     • In class diagrams, we can connect two classes with a solid line.

  2. Multiplicity:

     • Multiplicity of Association tells us: how many objects of each class take part in the relationship?

  3. Generalization/Inheritence:

     • Parent-child class relationship

  4. Aggregation:

     • Whenever we need to represent any class that is a part of another class, we can use aggregation.

• Object diagram:

  • We use OBJECT DIAGRAMS to show objects in software designs.

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Use Case Diagram:

• In UML, use case diagrams are high level diagrams.
• It provides a basic high level view about the system.
• Four major components are:

  • System:

    • The application/software component we are going to develop.

  • Actor:

    • Any external agent that can interact with the system.

    • Two types:

      1. Primary Actors (on the left side of use case diagram)
         • Responsible for initiating action.
      2. Secondary Actors (on the right side of use case diagram)
         • Responsible for Response/Reactions

      

  • Use-Case:

    • Shows task within the system. Example: Registration, Login, Search, etc.

  • Relationship:

    • Relationship are represented by solid line from actors to use-case.

    • Types:

      1. Association (between actors and use-case)
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      2. Inclusive (base use-case -> inclusive use-case)
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      3. Dependent
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      4. Inheritance
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    Final diagram:

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