Question

SYSTEM ENGINEERING

Compare and contrast the waterfall, spiral, cycle, and Vee models of the systems engineering process. In particular, what (e.g., functions performed, time sequence of functions, outputs produced, interaction with stakeholders) is the same in each of these processes and what is different? Are there some categories of systems for which one process would be better than the others? Use outside references to gain more information on the Waterfall, Spiral, Cycle and Vee models.

Answer 1

The Waterfall Model The waterfall model is the classical model of software engineering. This model is one of the oldest models and is widely used in government projects and in many major companies. As this model emphasizes planning in early stages, it ensures design flaws before they develop. In addition, its intensive document and planning make it work well for projects in which quality control is a major concern. The pure waterfall lifecycle consists of several nonoverlapping stages, as shown in the following figure. The model begins with establishing system requirements and software requirements and continues with architectural design, detailed design, coding, testing, and maintenance. The waterfall model serves as a baseline for many other lifecycle models.

Requirement Analysis Waterfall Model System Design Implementation Testing Deployment Maintenance

1.System requirements: Establishes the components for building the system, including the hardware requirements, software tools, and other necessary components..

2 Software requirements: Establishes the expectations for software functionality and identifies which system requirements the software affects. Requirements analysis includes determining interaction needed with other applications and databases, performance requirements, user interface requirements, and so on.

3 Architectural design: Determines the software framework of a system to meet the specific requirements. This design defines the major components and the interaction of those components, but it does not define the structure of each component. The external interfaces and tools used in the project can be determined by the designer.

4 Detailed design: Examines the software components defined in the architectural design stage and produces a specification for how each component is implemented.

5 Coding: Implements the detailed design specification.

6 Testing: Determines whether the software meets the specified requirements and finds any errors present in the code.

7 Maintenance: Addresses problems and enhancement requests after the software releases.

V-Shaped

Model Just like the waterfall model, the V-Shaped life cycle is a sequential path of execution of processes. Each phase must be completed before the next phase begins. Testing is emphasized in this model more than the waterfall model. The testing procedures are developed early in the life cycle before any coding is done, during each of the phases preceding implementation. Requirements begin the life cycle model just like the waterfall model. Before development is started, a system test plan is created. The test plan focuses on meeting the functionality specified in requirements gathering. The high-level design phase focuses on system architecture and design. An integration test plan is created in this phase in order to test the pieces of the software systems ability to work together. However, the low-level design phase lies where the actual software components are designed, and unit tests are created in this phase as well. The implementation phase is, again, where all coding takes place. Once coding is complete, the path of execution continues up the right side of the V where the test plans developed earlier are now put to use.

Requirements like BRS and SRS begin the life cycle model just like the waterfall model. But, in this model before development is started, a system test plan is created. The test plan focuses on meeting the functionality specified in the requirements gathering.

The high-level design (HLD) phase focuses on system architecture and design. It provide overview of solution, platform, system, product and service/process. Anintegration test plan is created in this phase as well in order to test the pieces of the software systems ability to work together.

The low-level design (LLD) phase is where the actual software components are designed. It defines the actual logic for each and every component of the system. Class diagram with all the methods and relation between classes comes under LLD. Component tests are created in this phase as well.

The implementation phase is, again, where all coding takes place. Once coding is complete, the path of execution continues up the right side of the V where the test plans developed earlier are now put to use.

Coding: This is at the bottom of the V-Shape model. Module design is converted into code by developers.

Spiral model

The spiral mode was introduced due to shortcoming inthe waterfall prototype model of software engineering it is the combination of the said two model of the software development from the rame of the model it can derived that the actvites of the software development are carried out like a spiral

1. Determine Objectives: Identify the system life-cycle stakeholders and their win conditions and establish initial system boundaries and external interfaces.

2. Determine Constraints: Determine the conditions under which the system would produce win-lose or loselose outcomes for some stakeholders.

3. Identify and Evaluate Alternatives: Solicit suggestions from stakeholders, evaluate them with respect to stakeholders' win conditions, synthesize and negotiate candidate win-win alternatives, analyze, assess, resolve win-lose or lose-lose risks, record commitments and areas to be left flexible in the project's design record and life cycle plans.

4. Cycle through the Spiral: Elaborate the win conditions evaluate and screen alternatives, resolve risks, accumulate appropriate commitments, and develop and execute downstream plans