OBJECT ORIENTED ANALYSIS & DESIGN

Structured Analysis and structured Design

1. 
   Reduce maintenance time and effort
2. 
   Makes it easier to go back to earlier phases in the life cycle when necessary.
3. Emphasis on portioning or dividing a problem into smaller, more manageable units and making a clear distinction between physical and logical design.

Object –oriented Analysis and design
 

1. OOAD is a third approach to system development, after the process –oriented and data-oriented approaches
2. Systems development methodologies and techniques based on objects rather than data or processes.
3. The goal of OOAD is to make system elements more reusable thus improving system quality and the productivity of systems analysis and design.
4. 
   The primary tasks of object oriented analysis are identifying objects, defining their structure and behavior and defining their relationship.
5. The primary tasks of OOD are modeling the details of the object's behavior and communication with other objects so that system requirements are met and reexamining and redefining objects to better take advantage of inheritance and other benefits of object-orientation.

-With traditional system development and structured techniques analysis and design are separate but
overlapping steps, and different techniques are used for analysis and for design.
- Object-oriented model is popular because of its ability to thoroughly represent complex relationship, as
well as to represent data and data processing with consistent notation.
- A model is an abstraction of the real world and it allows us to deal l with the complexity inherent in a realworld
problem by focusing on the essential and interesting features of an application.
- The principles of objects, encapsulation, inheritance and polymorphism are the foundation for objectoriented
system development.

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spiral model

Advantages of spiral model

1. It is risk driven model. It is very flexible
2. Less documentation is needed.
3. It uses prototyping

Limitations of Spiral Model

1. No strict standards for software development
2. No particular beginning or end of particular phase

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Prototyping models

Advantages of Prototyping models

1. Suitable for large system for which there is no manual process to define the
requirements
2. User training to use the system
3. User services determination
4. System training
5. Quality of software is good
6. Requirements are not freezed.

Limitation of Prototyping Mode

1. It was difficult to find all the requirements of the software initially.
2. It was very difficult to predict how the system will be after development.
These two limitations will be removed in the prototyping model. First limitation is
removing by unfreezing the requirements before any design or coding can proceed.
Second limitation is remove by making a throw away prototype to understand the
requirements.

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waterfall model

Advantages of waterfall mode

1. It is a linear model
2. It is a segmental model
3. It is systematic and sequential
4. It is simple one
5. Its has proper documentations


Disadvantages of waterfall model

1. It is difficult to define all requirements at the beginning of project
2. This model is not suitable for accommodating any change
3. A working version of the system is not seen until late in the project's life.
4. It does not scale up well to large project
5. it involves heavy documentation
6. We cannot go in the background direction while SDLC performs
7. There is no sample model for clearly in realization the customers needs.
8. There is no risk analysis
9. If there is any mistake or error in any phase then we cannot make goon software
10. It is a document driven process that requires formal documents at the end of each phase.

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Designing the Internals: Program and Process Design

Introduction.

Once you know the input, the output, the interface, the dialogue, and database for an information
systems, you can design the inside of the system, the part that will make the interface operable, generate
output, and access and update the organization's databases. (Internal design).
We will begin at an abstract level, taking what we already know about a system's processs, in the form
of documented data flow diagrams, and converting them to structure charts. Structure charts graphically
represent system design. The structure charts you create will form the basis for the structure of the
system you design and build. Decisions you make at this point will heavily influence the overall design
and implementation of your system information.

Design the Internals:

The process of designing the internals.
You begin designing internals armed with a great deal of information about the system chosen for
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development and implementation. With the exception of the detailed physical file and database design,
most of that information is at logical level. For the process that have been identified as part of the
system, the information takes the form of data flow diagrams and mostly textual descriptions of what
each process is supposed to accomplish. Your job now is to take the logical information and turn it into a
blueprint for the physical information system that will be programmed.

Structure Charts:

Structure charts:
􀂊 Hierarchical diagram that shows how information system is organized.
􀂊 Shows how parts of system are related to one another
􀂊 Shows breakdown of a system into programs and internal structures of programs written in
third and fourth generation languages.

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