Knowledge in sdlc
SOFTWARE ENGINEERING RAJIB MALL TEXTBOOK and SOLUTIONS
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SDLC - Software Development Life Cycle
SDLC - Overview Software Development Life Cycle (SDLC) is a process used by the 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.· 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.The following figure is a graphical representation of the various stages of a typical SDLC.A typical Software Development Life Cycle consists of the following stages −Stage 1: Planning and Requirement AnalysisRequirement 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 RequirementsOnce 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 an 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 ArchitectureSRS 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 ProductIn 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 must 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.Stage 5: Testing the ProductThis 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 product 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 MaintenanceOnce the product is tested and ready to be deployed it is released formally in the appropriate market. Sometimes product deployment happens in stages as per the business strategy of that organization. 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 ModelsThere are various software development life cycle models defined and designed which are followed during the 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 to ensure success in the process of software development.Following are the most important and popular SDLC models followed in the industry −Waterfall ModelIterative ModelSpiral ModelV-ModelBig Bang ModelOther related methodologies are Agile Model, RAD Model, Rapid Application Development and Prototyping Models.
kaushal shah
Waterfall Model
SDLC - Waterfall Model The Waterfall Model was the 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.The 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. This means that any phase in the development process begins only if the previous phase is complete. In this waterfall model, the phases do not overlap.Waterfall Model - DesignWaterfall 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 this Waterfall model, typically, the outcome of one phase acts as the input for the next phase sequentially.The following illustration is a representation of the different phases of the Waterfall Model.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 document.· System Design − The requirement specifications from first phase are studied in this phase and the system design is prepared. This system design helps in specifying hardware and system requirements and helps in defining the overall system architecture.· Implementation − With inputs from the 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.Waterfall Model - ApplicationEvery 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 - AdvantagesThe advantages of waterfall development are 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.Some of the major advantages of the Waterfall Model are as follows −· 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.Waterfall Model - DisadvantagesThe disadvantage of waterfall development is that it does not allow 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.The major disadvantages of the Waterfall Model are as follows −· 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 are 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.
Spiral Model
SDLC - Spiral Model The spiral model combines the idea of iterative development with the systematic, controlled aspects of the waterfall model. This Spiral model is a combination of iterative development process model and sequential linear development model i.e. the waterfall model with a very high emphasis on risk analysis. It allows incremental releases of the product or incremental refinement through each iteration around the spiral.Spiral Model - DesignThe spiral model has four phases. A software project repeatedly passes through these phases in iterations called Spirals.IdentificationThis phase starts with gathering the business requirements in the baseline spiral. In the subsequent spirals as the product matures, identification of system requirements, subsystem requirements and unit requirements are all done in this phase.This phase also includes understanding the system requirements by continuous communication between the customer and the system analyst. At the end of the spiral, the product is deployed in the identified market.DesignThe Design phase starts with the conceptual design in the baseline spiral and involves architectural design, logical design of modules, physical product design and the final design in the subsequent spirals.Construct or BuildThe Construct phase refers to production of the actual software product at every spiral. In the baseline spiral, when the product is just thought of and the design is being developed a POC (Proof of Concept) is developed in this phase to get customer feedback.Then in the subsequent spirals with higher clarity on requirements and design details a working model of the software called build is produced with a version number. These builds are sent to the customer for feedback.Evaluation and Risk AnalysiRisk Analysis includes identifying, estimating and monitoring the technical feasibility and management risks, such as schedule slippage and cost overrun. After testing the build, at the end of first iteration, the customer evaluates the software and provides feedback.The following illustration is a representation of the Spiral Model, listing the activities in each phase.Based on the customer evaluation, the software development process enters the next iteration and subsequently follows the linear approach to implement the feedback suggested by the customer. The process of iterations along the spiral continues throughout the life of the software.Spiral Model ApplicationThe Spiral Model is widely used in the software industry as it is in sync with the natural development process of any product, i.e. learning with maturity which involves minimum risk for the customer as well as the development firms.The following pointers explain the typical uses of a Spiral Model −· When there is a budget constraint and risk evaluation is important.· For medium to high-risk projects.· Long-term project commitment because of potential changes to economic priorities as the requirements change with time.· Customer is not sure of their requirements which is usually the case.· Requirements are complex and need evaluation to get clarity.· New product line which should be released in phases to get enough customer feedback.· Significant changes are expected in the product during the development cycle.Spiral Model - Pros and ConsThe advantage of spiral lifecycle model is that it allows elements of the product to be added in, when they become available or known. This assures that there is no conflict with previous requirements and design.This method is consistent with approaches that have multiple software builds and releases which allows making an orderly transition to a maintenance activity. Another positive aspect of this method is that the spiral model forces an early user involvement in the system development effort.On the other side, it takes a very strict management to complete such products and there is a risk of running the spiral in an indefinite loop. So, the discipline of change and the extent of taking change requests is very important to develop and deploy the product successfully.The advantages of the Spiral SDLC Model are as follows −· Changing requirements can be accommodated.· Allows extensive use of prototypes.· Requirements can be captured more accurately.· Users see the system early.· Development can be divided into smaller parts and the risky parts can be developed earlier which helps in better risk management.The disadvantages of the Spiral SDLC Model are as follows −· Management is more complex.· End of the project may not be known early.· Not suitable for small or low risk projects and could be expensive for small projects.· Process is complex· Spiral may go on indefinitely.· Large number of intermediate stages requires excessive documentation.
RAD -Rapid Application Development
SDLC - RAD Model The RAD (Rapid Application Development) model is based on prototyping and iterative development with no specific planning involved. The process of writing the software itself involves the planning required for developing the product.Rapid Application Development focuses on gathering customer requirements through workshops or focus groups, early testing of the prototypes by the customer using iterative concept, reuse of the existing prototypes (components), continuous integration and rapid delivery.What is RAD?Rapid application development is a software development methodology that uses minimal planning in favour of rapid prototyping. A prototype is a working model that is functionally equivalent to a component of the product.In the RAD model, the functional modules are developed in parallel as prototypes and are integrated to make the complete product for faster product delivery. Since there is no detailed preplanning, it makes it easier to incorporate the changes within the development process.RAD projects follow iterative and incremental model and have small teams comprising of developers, domain experts, customer representatives and other IT resources working progressively on their component or prototype.The most important aspect for this model to be successful is to make sure that the prototypes developed are reusable.RAD Model DesignRAD model distributes the analysis, design, build and test phases into a series of short, iterative development cycles.Following are the various phases of the RAD Model −Business ModelingThe business model for the product under development is designed in terms of flow of information and the distribution of information between various business channels. A complete business analysis is performed to find the vital information for business, how it can be obtained, how and when is the information processed and what are the factors driving successful flow of information.Data ModelingThe information gathered in the Business Modeling phase is reviewed and analyzed to form sets of data objects vital for the business. The attributes of all data sets is identified and defined. The relation between these data objects are established and defined in detail in relevance to the business model.Process ModelingThe data object sets defined in the Data Modeling phase are converted to establish the business information flow needed to achieve specific business objectives as per the business model. The process model for any changes or enhancements to the data object sets is defined in this phase. Process descriptions for adding, deleting, retrieving or modifying a data object are given.Application GenerationThe actual system is built and coding is done by using automation tools to convert process and data models into actual prototypes.Testing and TurnoverThe overall testing time is reduced in the RAD model as the prototypes are independently tested during every iteration. However, the data flow and the interfaces between all the components need to be thoroughly tested with complete test coverage. Since most of the programming components have already been tested, it reduces the risk of any major issues.RAD Model Vs Traditional SDLCThe traditional SDLC follows a rigid process models with high emphasis on requirement analysis and gathering before the coding starts. It puts pressure on the customer to sign off the requirements before the project starts and the customer doesn’t get the feel of the product as there is no working build available for a long time.The customer may need some changes after he gets to see the software. However, the change process is quite rigid and it may not be feasible to incorporate major changes in the product in the traditional SDLC.The RAD model focuses on iterative and incremental delivery of working models to the customer. This results in rapid delivery to the customer and customer involvement during the complete development cycle of product reducing the risk of non-conformance with the actual user requirements.RAD Model – ApplicationRAD model can be applied successfully to the projects in which clear modularization is possible. If the project cannot be broken into modules, RAD may fail.The following pointers describe the typical scenarios where RAD can be used −· RAD should be used only when a system can be modularized to be delivered in an incremental manner.· It should be used if there is a high availability of designers for modeling.· It should be used only if the budget permits use of automated code generating tools.· RAD SDLC model should be chosen only if domain experts are available with relevant business knowledge.· Should be used where the requirements change during the project and working prototypes are to be presented to customer in small iterations of 2-3 months.RAD Model - Pros and ConsRAD model enables rapid delivery as it reduces the overall development time due to the reusability of the components and parallel development. RAD works well only if high skilled engineers are available and the customer is also committed to achieve the targeted prototype in the given time frame. If there is commitment lacking on either side the model may fail.The advantages of the RAD Model are as follows −· Changing requirements can be accommodated.· Progress can be measured.· Iteration time can be short with use of powerful RAD tools.· Productivity with fewer people in a short time.· Reduced development time.· Increases reusability of components.· Quick initial reviews occur.· Encourages customer feedback.· Integration from very beginning solves a lot of integration issues.The disadvantages of the RAD Model are as follows −· Dependency on technically strong team members for identifying business requirements.· Only system that can be modularized can be built using RAD.· Requires highly skilled developers/designers.· High dependency on modeling skills.· Inapplicable to cheaper projects as cost of modeling and automated code generation is very high.· Management complexity is more.· Suitable for systems that are component based and scalable.· Requires user involvement throughout the life cycle.· Suitable for project requiring shorter development times.
Iterative Model
SDLC - Iterative Model In the Iterative model, iterative process starts with a simple implementation of a small set of the software requirements and iteratively enhances the evolving versions until the complete system is implemented and ready to be deployed.An iterative life cycle model does not attempt to start with a full specification of requirements. Instead, development begins by specifying and implementing just part of the software, which is then reviewed to identify further requirements. This process is then repeated, producing a new version of the software at the end of each iteration of the model.Iterative Model - DesignIterative 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).The following illustration is a representation of the Iterative and Incremental model –Iterative and Incremental development is a combination of both iterative design or iterative method and incremental build model for development. "During software development, more than one iteration of the software development cycle may be in progress at the same time." This process may be described as an "evolutionary acquisition" or "incremental build" approach."In this incremental model, the whole requirement is divided into various builds. During each iteration, the development module goes through the requirements, design, implementation and testing phases. Each subsequent release of the module adds function to the previous release. The process continues till the complete system is ready as per the requirement.The key to a successful use of an iterative software development lifecycle is rigorous validation of requirements, and verification & testing of each version of the software against those requirements within each cycle of the model. As the software evolves through successive cycles, tests must be repeated and extended to verify each version of the software.Iterative Model - ApplicationLike 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.· A new technology is being used and is being learnt by the development team while working on the project.· Resources with needed skill sets 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 ConsThe 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.The advantages of the Iterative and Incremental SDLC Model are as follows −· 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.· Easier to manage risk - High risk part is done first.· With every increment, operational product is delivered.· Issues, challenges and risks identified from each increment can be utilized/applied to the next increment.· Risk analysis is better.· It supports changing requirements.· Initial Operating time is less.· Better suited for large and mission-critical projects.· During the life cycle, software is produced early which facilitates customer evaluation and feedback.The disadvantages of the Iterative and Incremental SDLC Model are as follows −· 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.
MANAGING THE SOFTWARE SYSTEM
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DBMS APPLICATION DESIGN AND DEVELOPMENT
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