SPM/U1 Topic 6 Evolutionary Software Process Models
Evolutionary Process Models
- Evolutionary models are iterative type models.
- They allow to develop more complete versions of the software.
Following are the evolutionary process models.
1. The prototyping model
2. The spiral model
3. Concurrent development model
- The Prototyping model
- Prototype is defined as first or preliminary form using which other forms are copied or derived.
- Prototype model is a set of general objectives for software.
- It does not identify the requirements like detailed input, output.
- It is software working model of limited functionality.
- In this model, working programs are quickly produced.
The different phases of Prototyping model are:
In this phase, developer and customer meet and discuss the overall objectives of the software.
2. Quick design
- Quick design is implemented when requirements are known.
- It includes only the important aspects like input and output format of the software.
- It focuses on those aspects which are visible to the user rather than the detailed plan.
- It helps to construct a prototype.
3. Modeling quick design
- This phase gives the clear idea about the development of software because the software is now built.
- It allows the developer to better understand the exact requirements.
4. Construction of prototype
The prototype is evaluated by the customer itself.
5. Deployment, delivery, feedback
- If the user is not satisfied with current prototype then it refines according to the requirements of the user.
- The process of refining the prototype is repeated until all the requirements of users are met.
- When the users are satisfied with the developed prototype then the system is developed on the basis of final prototype.
Advantages of Prototyping Model
- Prototype model need not know the detailed input, output, processes, adaptability of operating system and full machine interaction.
- In the development process of this model users are actively involved.
- The development process is the best platform to understand the system by the user.
- Errors are detected much earlier.
- Gives quick user feedback for better solutions.
- It identifies the missing functionality easily. It also identifies the confusing or difficult functions.
Disadvantages of Prototyping Model:
- The client involvement is more and it is not always considered by the developer.
- It is a slow process because it takes more time for development.
- Many changes can disturb the rhythm of the development team.
- It is a thrown away prototype when the users are confused with it.
2. The Spiral model
- Spiral model is a risk driven process model.
- It is used for generating the software projects.
- In spiral model, an alternate solution is provided if the risk is found in the risk analysis, then alternate solutions are suggested and implemented.
- It is a combination of prototype and sequential model or waterfall model.
- In one iteration all activities are done, for large project’s the output is small.
The framework activities of the spiral model are as shown in the following figure.
NOTE: The description of the phases of the spiral model is same as that of the process model.
Advantages of Spiral Model
- It reduces high amount of risk.
- It is good for large and critical projects.
- It gives strong approval and documentation control.
- In spiral model, the software is produced early in the life cycle process.
Disadvantages of Spiral Model
- It can be costly to develop a software model.
- It is not used for small projects.
3. The concurrent development model
- The concurrent development model is called as concurrent model.
- The communication activity has completed in the first iteration and exits in the awaiting changes state.
- The modeling activity completed its initial communication and then go to the underdevelopment state.
- If the customer specifies the change in the requirement, then the modeling activity moves from the under development state into the awaiting change state.
- The concurrent process model activities moving from one state to another state.
Advantages of the concurrent development model
- This model is applicable to all types of software development processes.
- It is easy for understanding and use.
- It gives immediate feedback from testing.
- It provides an accurate picture of the current state of a project.
Disadvantages of the concurrent development model
- It needs better communication between the team members. This may not be achieved all the time.
- It requires to remember the status of the different activities.