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530_project_2a.pptxLife Cycle of System Development
Life cycle of System development
SDLC, Software Development Life Cycle is a process used by software industry to design, develop and test high quality softwares. The SDLC aims to produce a high quality software that meets or exceeds customer expectations, reaches completion within times and cost estimates.
SDLC is the acronym of Software Development Life Cycle.
It is also called as Software development process.
The software development life cycle (SDLC) is a framework defining tasks performed at each step in the software development process.
ISO/IEC 12207 is an international standard for software life-cycle processes. It aims to be the standard that defines all the tasks required for developing and maintaining software.
What is SDLC?
SDLC is a process followed for a software project, within a software organization. It consists of a detailed plan describing how to develop, maintain, replace and alter or enhance specific software. The life cycle defines a methodology for improving the quality of software and the overall development process.
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Stages of SDLC
The following figure is a graphical representation of the various stages of a typical SDLC.
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Software Development life cycle consists of the following stages:
Stage 1: Planning and Requirement Analysis
Requirement analysis is the most important and fundamental stage in SDLC. It is performed by the senior members of the team with inputs from the customer, the sales department, market surveys and domain experts in the industry. This information is then used to plan the basic project approach and to conduct product feasibility study in the economical, operational, and technical areas.
Planning for the quality assurance requirements and identification of the risks associated with the project is also done in the planning stage. The outcome of the technical feasibility study is to define the various technical approaches that can be followed to implement the project successfully with minimum risks.
Stage 2: Defining Requirements
Once the requirement analysis is done the next step is to clearly define and document the product requirements and get them approved from the customer or the market analysts. This is done through .SRS. . Software Requirement Specification document which consists of all the product requirements to be designed and developed during the project life cycle.
Stage 3: Designing the product architecture
SRS is the reference for product architects to come out with the best architecture for the product to be developed. Based on the requirements specified in SRS, usually more than one design approach for the product architecture is proposed and documented in a DDS - Design Document Specification.
This DDS is reviewed by all the important stakeholders and based on various parameters as risk assessment, product robustness, design modularity , budget and time constraints , the best design approach is selected for the product.
A design approach clearly defines all the architectural modules of the product along with its communication and data flow representation with the external and third party modules (if any). The internal design of all the modules of the proposed architecture should be clearly defined with the minutest of the details in DDS.
Stage 4: Building or Developing the Product
In this stage of SDLC the actual development starts and the product is built. The programming code is generated as per DDS during this stage. If the design is performed in a detailed and organized manner, code generation can be accomplished without much hassle.
Developers have to follow the coding guidelines defined by their organization and programming tools like compilers, interpreters, debuggers etc are used to generate the code. Different high level programming languages such as C, C++, Pascal, Java, and PHP are used for coding. The programming language is chosen with respect to the type of software being developed.
Other stages
Stage 5: Testing the Product
This stage is usually a subset of all the stages as in the modern SDLC models, the testing activities are mostly involved in all the stages of SDLC. However this stage refers to the testing only stage of the product where products defects are reported, tracked, fixed and retested, until the product reaches the quality standards defined in the SRS.
Stage 6: Deployment in the Market and Maintenance
Once the product is tested and ready to be deployed it is released formally in the appropriate market. Sometime product deployment happens in stages as per the organizations. business strategy. The product may first be released in a limited segment and tested in the real business environment (UAT- User acceptance testing).
Then based on the feedback, the product may be released as it is or with suggested enhancements in the targeting market segment. After the product is released in the market, its maintenance is done for the existing customer base.
SDLC Models
Following are the most important and popular SDLC models followed in the industry:
Waterfall Model
Iterative Model
Spiral Model
V-Model
Big Bang Model
There are various software development life cycle models defined and designed which are followed during software development process. These models are also referred as "Software Development Process Models". Each process model follows a Series of steps unique to its type, in order to ensure success in process of software development.
The other related methodologies are Agile Model, RAD Model, Rapid Application Development and Prototyping Models.
The Waterfall Model was first Process Model to be introduced. It is also referred to as a linear-sequential life cycle model. It is very simple to understand and use. In a waterfall model, each phase must be completed before the next phase can begin and there is no overlapping in the phases.
Waterfall model is the earliest SDLC approach that was used for software development .
The waterfall Model illustrates the software development process in a linear sequential flow; hence it is also referred to as a linear-sequential life cycle model. This means that any phase in the development process begins only if the previous phase is complete. In waterfall model phases do not overlap.
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Waterfall Model design
Waterfall approach was first SDLC Model to be used widely in Software Engineering to ensure success of the project. In "The Waterfall" approach, the whole process of software development is divided into separate phases. In Waterfall model, typically, the outcome of one phase acts as the input for the next phase sequentially.
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The sequential phases in Waterfall model are:
Requirement Gathering and analysis: All possible requirements of the system to be developed are captured in this phase and documented in a requirement specification doc.
System Design: The requirement specifications from first phase are studied in this phase and system design is prepared. System Design helps in specifying hardware and system requirements and also helps in defining overall system architecture.
Implementation: With inputs from system design, the system is first developed in small programs called units, which are integrated in the next phase. Each unit is developed and tested for its functionality which is referred to as Unit Testing.
Integration and Testing: All the units developed in the implementation phase are integrated into a system after testing of each unit. Post integration the entire system is tested for any faults and failures.
Deployment of system: Once the functional and non functional testing is done, the product is deployed in the customer environment or released into the market.
Maintenance: There are some issues which come up in the client environment. To fix those issues patches are released. Also to enhance the product some better versions are released. Maintenance is done to deliver these changes in the customer environment.
All these phases are cascaded to each other in which progress is seen as flowing steadily downwards (like a waterfall) through the phases. The next phase is started only after the defined set of goals are achieved for previous phase and it is signed off, so the name "Waterfall Model". In this model phases do not overlap.
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Waterfall Model Application
Every software developed is different and requires a suitable SDLC approach to be followed based on the internal and external factors. Some situations where the use of Waterfall model is most appropriate are:
Requirements are very well documented, clear and fixed.
Product definition is stable.
Technology is understood and is not dynamic.
There are no ambiguous requirements.
Ample resources with required expertise are available to support the product.
The project is short.
Waterfall Model Pros & Cons
| Pros | Cons |
| Simple and easy to understand and use Easy to manage due to the rigidity of the model . each phase has specific deliverables and a review process. Phases are processed and completed one at a time. Works well for smaller projects where requirements are very well understood. Clearly defined stages. Well understood milestones. Easy to arrange tasks. Process and results are well documented. | No working software is produced until late during the life cycle. High amounts of risk and uncertainty. Not a good model for complex and object-oriented projects. Poor model for long and ongoing projects. Not suitable for the projects where requirements are at a moderate to high risk of changing. So risk and uncertainty is high with this process model. It is difficult to measure progress within stages. Cannot accommodate changing requirements. Adjusting scope during the life cycle can end a project. Integration is done as a "big-bang. at the very end, which doesn't allow identifying any technological or business bottleneck or challenges early. |
Advantage
The advantage of waterfall development is that it allows for departmentalization and control. A schedule can be set with deadlines for each stage of development and a product can proceed through the development process model phases one by one.
Development moves from concept, through design, implementation, testing, installation, troubleshooting, and ends up at operation and maintenance. Each phase of development proceeds in strict order.
Disadvantage
The disadvantage of waterfall development is that it does not allow for much reflection or revision. Once an application is in the testing stage, it is very difficult to go back and change something that was not well-documented or thought upon in the concept stage.
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Iterative Model design
Following is the pictorial representation of Iterative and Incremental model:
Iterative process starts with a simple implementation of a subset of the software requirements and iteratively enhances the evolving versions until the full system is implemented. At each iteration, design modifications are made and new functional capabilities are added. The basic idea behind this method is to develop a system through repeated cycles (iterative) and in smaller portions at a time (incremental).
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Iterative Model Application
Like other SDLC models, Iterative and incremental development has some specific applications in the software industry. This model is most often used in the following scenarios:
Requirements of the complete system are clearly defined and understood.
Major requirements must be defined; however, some functionalities or requested enhancements may evolve with time.
There is a time to the market constraint.
Resources with needed skill set are not available and are planned to be used on contract basis for specific iterations.
There are some high risk features and goals which may change in the future.
Iterative Model Pros and Cons
The following table lists out the pros and cons of Iterative and Incremental SDLC Model:
| Pros | Cons |
| Some working functionality can be developed quickly and early in the life cycle. Results are obtained early and periodically. Parallel development can be planned. Progress can be measured. Less costly to change the scope/requirements. Testing and debugging during smaller iteration is easy. Risks are identified and resolved during iteration; and each iteration is an easily managed milestone. With every increment operational product is delivered. Issues, challenges & risks identified from each increment can be utilized/applied to the next increment. Risk analysis is better Initial Operating time is less During life cycle software is produced early which facilitates customer evaluation and feedback. | More resources may be required. Although cost of change is lesser but it is not very suitable for changing requirements. More management attention is required. System architecture or design issues may arise because not all requirements are gathered in the beginning of the entire life cycle. Defining increments may require definition of the complete system. Not suitable for smaller projects. Management complexity is more. End of project may not be known which is a risk. Highly skilled resources are required for risk analysis. Project.s progress is highly dependent upon the risk analysis p |
The advantage of this model is that there is a working model of the system at a very early stage of development which makes it easier to find functional or design flaws. Finding issues at an early stage of development enables to take corrective measures in a limited budget.
The disadvantage with this SDLC model is that it is applicable only to large and bulky software development projects. This is because it is hard to break a small software system into further small serviceable increments/modules.
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Other models
Waterfall and V model are traditional SDLC models and are of sequential type. Sequential means that the next phase can start only after the completion of first phase. Such models are suitable for projects with very clear product requirements and where the requirements will not change dynamically during the course of project completion.
Iterative and Spiral models are more accommodative in terms of change and are suitable for projects where the requirements are not so well defined, or the market requirements change quite frequently.
Big Bang model is a random approach to Software development and is suitable for small or academic projects.
Agile is the most popular model used in the industry. Agile introduces the concept of fast delivery to customers using prototype approach. Agile divides the project into small iterations with specific deliverable features. Customer interaction is the backbone of Agile methodology, and open communication with minimum documentation are the typical features of Agile development environment.
RAD (Rapid Application Development) and Software Prototype are modern techniques to understand the requirements in a better way early in the project cycle. These techniques work on the concept of providing a working model to the customer and stockholders to give the look and feel and collect the feedback. This feedback is used in an organized manner to improve the product.
We have discussed all the popular SDLC models in the industry, both traditional and Modern. This tutorial also gives you an insight into the pros and cons and the practical applications of the SDLC models discussed.
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COTS (Commercial Off-The-Shelf) Specifications to our business:
COTS determination:
COTS programming choices have expanded to a great degree high late years. Bunks sister is the SaaS, Software as an administration.
Client experience about COTS:
Truly an extended period of time back I may have spent upwards of 5 thousand to get a site up and running. Today, with Word Press and some monetarily keen encouraging courses of action, a huge amount of effort and a little help from my mates, I'm running a site. In case you scale up two or three endeavors in size, there are gadgets like SalesForce.com and QuickBooks online that make it decently, basic for associations to impact ERP-like parts without the ERP-style costs.
Ex:
Workday
Salesforce
Kronos
No establishment and no server support obliged, everything would be in cloud, pay per use mechanism. Free layouts everything gave by cloud you can fabricate your surroundings without correcting a solitary line code.
Advantages and Disadvantages using COTS:
| Advantages COTS | Disadvantages COTS |
| Low starting speculation | Most engaging element is cost |
| Significant cash sparing. | Highlights that your business needn't bother with. |
| You are not fulfilled by item your cash will back. | Isn't intended to oblige future needs |
| Speedy convey contrasted with client | |
| It ought to help your representatives work more brilliant |
We have a rundown of favorable circumstances promotion detriments utilizing COTS few of the points of interest above,
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