Outline:• Object Oriented Design – Overview• Object Oriented Design - Methods• HOOD – Overview• HOOD – The Basic Design Step• HOOD – Notation• HOOD – Example

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Three OOD principles that improve software design for reliability, maintainability, and reusability.

• Abstraction: Objects are an abstraction of part of the real-world. More maintainable and reusable.

• Encapsulation: Objects hide their internal contents from other components to improve maintainability. (information hiding)

• Inheritance: Organizing objects in class hierarchies to promote reuse. (subclass, superclass, hierarchical, multiple, polymorphism)

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Hierarchical Object Oriented Design (HOOD)Object Oriented System Design (OOSD)Object Oriented System Analysis (OOSA)Object Oriented Analysis (OOA)ObjectOry

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• HOOD is a method of hierarchical decomposition of the design into software units based on identification of objects, classes and operations reflecting problem domain entities or more abstract objects related to digital programming entities.

• It is intended for the Architectural Design, Detailed Design and coding for software to be developed in programming languages such as Ada, C, or FORTRAN, as well as in object oriented languages such as C++, Ada95 or Eiffel.

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The main process in HOOD is called the Basic Design Step.

• "A Basic Design Step has as its goal the identification of child objects of a given parent object, and of their individual relationships to other existing objects, or the refinement of a terminal object to the level of the code. This process is based on the identification of objects by means of object-oriented design techniques”

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A basic design step process is further split into four phases, thus defining a micro life-cycle for a design step: -

1. Problem definition• Statement of the problem• Analysis and structuring of requirement data

2. Development of solution strategy3. Formalization of the strategy• Object identification. • Operation identification. • Grouping objects and operations (object operation table). • Graphical description. • Justification of design decisions.

4. Formalization of the solution04/12/23 6Sahib Babbar - sahib.babbar@gmail.com

Phase 1 : Problem Definition

The context of the object to be designed is stated, with the goal of organizing and structuring the data from the requirement analysis phase. This is an opportunity to provide a completeness check on requirements and traceability to design.

1. Statement of the problem - the designer states the problem in correct sentences which provides:- a clear and precise definition of the problem; - the context of the system to design.

2. Analysis and structuring of requirement data - the designer gathers and analyses all the information relevant to the problem, including the environment of the system to be designed.

Phase 1Problem definition

Phase 2Development of solution strategy

Phase 3Formalization of the

strategy

Phase 4Formalization of the

solution

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Phase 2 : Development of solution strategy

The outline solution of the problem stated above is described in terms of objects at a high level of abstraction.

Phase 1Problem definition

Phase 2Development of solution strategy

Phase 3Formalization of the

strategy

Phase 4Formalization of the

solution

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Phase 3 : Formalization of the strategy

The objects and their associated operations are defined. A HOOD diagram of the proposed design solution is produced, allowing easy visualization of the concepts and further formalization. There are five sub phases in the formalization of the strategy:

• Object identification. • Operation identification. • Grouping objects and operations (object operation table).• Graphical description. • Justification of design decisions.

Phase 1Problem definition

Phase 2Development of solution strategy

Phase 3Formalization of the

strategy

Phase 4Formalization of the

solution

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Phase 4 : Formalization of the solution

The solution is formalized through:• formal definition of provided object interfaces.• formal description of object and operation control

structures.

Phase 1Problem definition

Phase 2Development of solution strategy

Phase 3Formalization of the

strategy

Phase 4Formalization of the

solution

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The main diagram used for describing the structure of a system is the HOOD object diagram, which shows a static view of the structure in the hierarchical object oriented design. The symbols used are as follows:

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Person

name address national_insurance_no

Chare_timeEarn_salary

HireFire

Product

Product_name weight

Worker Manager

Department

Companynameaddressphoneproduct

works_for

manages

project

Project_nameBudgetpriority

Works

_on

Responsible_for

Manu-factures

Component Optional_extras

Thank You

Any ?

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