المحاضرة الثانية. Software life cycle and process model. Software processes. Although there are many software processes, some fundamental activities are common to all software processes:-
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1. Software specification :- The functionality of the software and constraints on its operation must be defined.
2. Software design and implementation :-The software to meet the specification must be produced.
3. Software validation:-The software must be validated to ensure that it does what the customer wants.
4. Software evolution :-The software must evolve to meet changing customer needs
The principal stages of the model onto fundamental development activities :-
1- Requirements analysis and definition :-
2- System and software design :-
3- Implementation and unit testing:-
4- Integration and system testing:-
5-Operation and maintenance :-
phase and that it fits with other engineering process models
Only appropriate when the requirement are well understood
There are two fundamental types of evolutionary development:
Objective is to work with customers and to evolve a final system from an initial outline specification. Should start with well-understood requirements and add new features as proposed by the customer.
Objective is to understand the system requirements. Should start with poorly understood requirements to clarify what is really needed.
from an engineering and management perspective, the evolutionary approach have two problems:
1- Systems are often poorly structured:- Continual change tends to corrupt the software structure
2- Systems are often poorly structured :-
Continual change tends to corrupt the software
1- Define requirements
2- Design system increment
3- Assign requirements to increment
4- Develop system increment
5- Test increment
6- Integrate system increment
7- Validate system
8- Final system
1- Customers do not have to wait until the entire system but use the software immediately
2- Customers can use the early increments as prototypes and gain experience that informs their requirements for later system increments
3-There is a lower risk of overall project failure. Although problems may be encountered in some increments, it is likely that will be successfully delivered to the customer
4- the highest priority services are delivered first, This means that customers are less likely to encounter software failures in the most important parts of the system