Assignment 4 (SAD 1)

Identify and discuss at least 3 systems development models .. discuss each phases ... (at least 500 words/model).
There are many systems development models that can help IT people and having these models there are strategies what should be done for the system and help create the algorithm of the program.
Before any software is made there is a process to go through to make it work. It passes through phases to make it as faultless as possible for the users. It might go through planning, coding, developing and other steps before one can create a software system work. This now relates to process model. If I were to define it from the word itself it is a flow of steps to organize the building or engineering of a software system. For a better understanding and for a more concrete definition, here follows the definition of process model from Wikipedia.
“Process models are processes of the same nature that are classified together into a model. Thus, a process model is a description of a process at the type level. Since the process model is at the type level, a process is an instantiation of it. The same process model is used repeatedly for the development of many applications and thus, has many instantiations. One possible use of a process model is to prescribe how things must/should/could be done in contrast to the process itself which is really what happens. A process model is roughly an anticipation of what the process will look like. What the process shall be will be determined during actual system development.”
According to Kerem Kosaner (2008), Process models are processes of the same nature that are classified together into a model. Thus, a process model is a description of a process at the type level. Since the process model is at the type level, a process is an instantiation of it. The same process model is used repeatedly for the development of many applications and thus, has many instantiations. One possible use of a process model is to prescribe how things must/should/could is done in contrast to the process itself which is really what happens. A process model is roughly an anticipation of what the process will look like. What the process shall be will be determined during actual system development. Here are some Process models:

Waterfall Model
It is one of a process model, by definition waterfall model is a popular version of the systems development life cycle model for software engineering. Often considered the classic approach to the systems development life cycle, the waterfall model describes a development method that is linear and sequential. Waterfall development has distinct goals for each phase of development. Imagine a waterfall on the cliff of a steep mountain. Once the water has flowed over the edge of the cliff and has begun its journey down the side of the mountain, it cannot turn back. It is the same with waterfall development. Once a phase of development is completed, the development proceeds to the next phase and there is no turning back. There are phases of Waterfall model here are the following :
Phase 1: A Software Requirements Specification (SRS) is a complete description of the behavior of the system to be developed. It includes a set of use cases that describe all the interactions the users will have with the software. Use cases are also known as functional requirements. In addition to use cases, the SRS also contains non-functional (or supplementary) requirements. Non-functional requirements are requirements which impose constraints on the design or implementation (such as performance engineering requirements, quality standards, or design constraints).
Phase 2: Software design is a process of problem-solving and planning for a software solution. After the purpose and specifications of software are determined, software developers will design or employ designers to develop a plan for a solution. It includes low-level component and algorithm implementation issues as well as the architectural view.
Phase 3: Implementation is a realization of a technical specification or algorithm as a program, software component, or other computer system. Many implementations may exist for a given specification or standard. For example, web browsers contain implementations of World Wide Web Consortium-recommended specifications, and software development tools contain implementations of programming languages.
In the IT Industry, implementation refers to post-sales process of guiding a client from purchase to use of the software or hardware that was purchased. This includes Requirements Analysis, Scope Analysis, Customizations, Systems Integrations, User Policies, User Training and Delivery. These steps are often overseen by a Project Manager using Project Management Methodologies set forth in the Project Management Body of Knowledge. Software Implementations involve several professionals that are relatively new to the knowledge based economy such as Business Analysts, Technical Analysts, Solutions Architect, and Project Managers.
Phase 4: Verification is a methodical process of finding and reducing the number of bugs, or defects, in a computer program or a piece of electronic hardware thus making it behave as expected. Debugging tends to be harder when various subsystems are tightly coupled, as changes in one may cause bugs to emerge in another.
Phase 5: Software maintenance in software engineering is the modification of a software product after delivery to correct faults, to improve performance or other attributes, or to adapt the product to a modified environment.

Spiral Model
The spiral model, also known as the spiral lifecycle model, is a systems development method (SDM) used in information technology (IT). This model of development combines the features of the prototyping model and the waterfall model. The spiral model is intended for large, expensive, and complicated projects.
This is the phase of the spiral model wherein we determine the objectives, alternatives and constraints.
Objectives: functionality, performance, hardware/software interface, critical success factors, etc.
Alternatives: build, reuse, buy, sub-contract, etc.
Constraints: cost, schedule, interface, etc.
The Spiral Model has its strengths as a process model and these are as follows:
• Provides early indication of insurmountable risks, without much cost
• Users see the system early because of rapid prototyping tools
• Critical high-risk functions are developed first
• The design does not have to be perfect
• Users can be closely tied to all lifecycle steps
• Early and frequent feedback from users
• Cumulative costs assessed frequently

If the Spiral Model has its strengths, it also has weakness as a process model. These are as follows:

• Time spent for evaluating risks too large for small or low-risk projects
• Time spent planning, resetting objectives, doing risk analysis and prototyping may be excessive
• The model is complex
• Risk assessment expertise is required
• Spiral may continue indefinitely
• Developers must be reassigned during non-development phase activities
• May be hard to define objective, verifiable milestones that indicate readiness to proceed through the next iteration

V-Model
One of the process model , by definition The V-model is a software development process which can be presumed to be the extension of the waterfall model. Instead of moving down in a linear way, the process steps are bent upwards after the coding phase, to form the typical V shape. The V-Model demonstrates the relationships between each phase of the development life cycle and its associated phase of testing.
The V-model deploys a well-structured method in which each phase can be implemented by the detailed documentation of the previous phase. Testing activities like test designing start at the beginning of the project well before coding and therefore saves a huge amount of the project time.
The V-model has a two major phases it is the Verification Phases and Validation Phases. In the verification phases it discuss the Requirements analysis, System Design, Architecture Design and Module Design and in the validation phases it discuss Unit Testing, Integration Testing, System Testing and User Acceptance Testing.

References:

http://www.acmesoffware.com/acme/default.asp
http://en.wikipedia.org/wiki/Capability_Maturity_Model
http://en.wikipedia.org/wiki/Waterfall_model
http://en.wikipedia.org/wiki/V-Model_