Software Process Models and Lifecycle Overview

PROJECT LIFE CYCLE AND EFFORT ESTIMATION Software Process and Process Models UNIT -II Dr.T.Logeswari Dept of CS

Software Process and Process Models Software Processes is a coherent set of activities for specifying, designing, implementing and testing software systems. A software process model is an abstract representation of a process that presents a description of a process from some particular perspective. There are many different software processes but all involve: Specification defining what the system should do; Design and implementation defining the organization of the system and implementing the system; Validation checking that it does what the customer wants; Evolution changing the system in response to changing customer needs.

Types of Software Process Model Software Process and Software Development Lifecycle Model One of the basic notions of the software development process is SDLC models which stands for Software Development Life Cycle models. Waterfall model V model Incremental model RAD model Agile model Iterative model Spiral model Prototype model

This model is a software life cycle where the stages are depicted as cascading from one to another. It was described by W.W. Royce in 1970. As the figure implies one development stage should be completed before the next begins Waterfall Model

1STMODEL: WATERFALL MODEL The requirement between the user and developer The requirement between the user and developer Requirement analysis data and architectural design to meet the requirement data and architectural design to meet the requirement Design programming language suitable fo programming language suitable for the project project r the Coding usi using different software ng different software testi testing methods and tools ng methods and tools Testing each phase each phase Maintenance

V Model The V-model represents a development process that may be considered an extension of the waterfall model and is an example of the more general V-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 horizontal and vertical axes represent time or project completeness (left-to-right) and level of abstraction (coarsest- grain abstraction uppermost), respectively.

Incremental model The incremental build model is a method of software development where the model is designed, implemented and tested incrementally (a little more is added each time) until the product is finished. It involves both development and maintenance. The product is defined as finished when it satisfies all of its requirements. Each iteration passes through the requirements, design, coding and testing phases. And each subsequent release of the system adds function to the previous release until all designed functionally has been implemented. This model combines the elements of the waterfall model with the iterative philosophy of prototyping.

Iterative Model In other words, the iterative approach begins by specifying and implementing just part of the software, which can then be reviewed and prioritized in order to identify further requirements. This iterative process is then repeated by delivering a new version of the software for each iteration. In a light-weight iterative project the code may represent the major source of documentation of the system; however, in a critical iterative project a formal software specification may also be required.

RAD model Rapid application development was a response to plan-driven waterfall processes, developed in the 1970s and 1980s, such as the Structured Systems Analysis and Design Method (SSADM). Rapid application development (RAD) is often referred as the adaptive software development. RAD is an incremental prototyping approach to software development that end users can produce better feedback when examining a live system, as opposed to working strictly with documentation. It puts less emphasis on planning and more emphasis on an adaptive process. RAD may resulted in a lower level of rejection when the application is placed into production, but this success most often comes at the expense of a dramatic overruns in project costs and schedule.

Spiral model was proposed by Boehm in 1988. Each loop in the spiral represents a phase of the software process. Innermost loop is concerned with system feasibility, next loop system requirement, followed by system design and so on Boehmia s Spiral Model

It has 2 distinguishing features: 1. One is cyclic approach for increment process system s. Degree of implementation while decreasing the degree of risk. 2. Other is a set of anchor point milestone for ensuring satisfactory system solution.

Each loop is split into 4 sectors 1.Objective setting Project risks are identified, alternative strategies depending on these risks may be planned. 2. Risk assessment and reduction - Project risks are identified detailed analysis carried steps taken to reduce risks. Ex: A prototype system (Toy like implementation with limited functional capabilities and low reliability just for the purpose of examining) 3.Development and Validation Choosing the most appropriate development model. 4.Planning Project is reviewed and decisions are made whether to continue with further loop of the spiral.

Agile model Agile is an umbrella term for a set of methods and practices based on the values and principles expressed in the Agile Manifesto that is a way of thinking that enables teams and businesses to innovate, quickly respond to changing demand, while mitigating risk. Organizations can be agile using many of the available frameworks available such as Scrum, Kanban, Lean, Extreme Programming (XP) and etc.

The primary goal of being Agile is empowered the development team the ability to create and respond to change in order to succeed in an uncertain and turbulent environment. Agile software development approach is typically operated in rapid and small cycles. This results in more frequent incremental releases with each release building on previous functionality. Thorough testing is done to ensure that software quality is maintained

PROJECT LIFE CYCLE AND EFFORT ESTIMATION Choice of Process Models UNIT - II Dr.T.Logeswari Dept of CS

The no. of inter related activities to create a final product can be organized in different ways and we can call these Process Models. A software process model is a simplified representation of a software process. Each model represents a process from a specific perspective. These generic models are abstractions of the process that can be used to explain different approaches to the software development. Any software process must include the following four activities: 1. Software specification (or requirements engineering): Define the main functionalities of the software and the constrains around them. 2. Software design and implementation: The software is to be designed and programmed. 3. Software verification and validation: The software must conform to its specification and meets the customer needs. 4. Software evolution (software maintenance): The software is being modified to meet customer and market requirements changes.

The various Process Models are Water Fall Model Spiral Model Prototype Model Incremental Delivery

Software Prototyping A prototype is a version of a system or part of the system that s developed quickly to check the customer s requirements or feasibility of some design decisions. So, a prototype is useful when a customer or developer is not sure of the requirements, or of algorithms, efficiency, business rules, response time, etc. In prototyping, the client is involved throughout the development process, which increases the likelihood of client acceptance of the final implementation. While some prototypes are developed with the expectation that they will be discarded, it is possible in some cases to evolve from prototype to working system.

The phases of a prototype are: 1. Establish objectives: The objectives of the prototype should be made explicit from the start of the process. Is it to validate system requirements, or demonstrate feasibility, etc. 2. Define prototype functionality: Decide what are the inputs and the expected output from a prototype. To reduce the prototyping costs and accelerate the delivery schedule, you may ignore some functionality, such as response time and memory utilization unless they are relevant to the objective of the prototype. 3. Develop the prototype: The initial prototype is developed that includes only user interfaces. 4. Evaluate the prototype: Once the users are trained to use the prototype, they then discover requirements errors. Using the feedback both the specifications and the prototype can be improved. If changes are introduced, then a repeat of steps 3 and 4 may be needed

Incremental Delivery Incremental development is based on the idea of developing an initial implementation, exposing this to user feedback, and evolving it through several versions until an acceptable system has been developed. The activities of a process are not separated but interleaved with feedback involved across those activities. Each system increment reflects a piece of the functionality that is needed by the customer. Generally, the early increments of the system should include the most important or most urgently required functionality. This means that the customer can evaluate the system at early stage in the development to see if it delivers what s required. If not, then only the current increment has to be changed and, possibly, new functionality defined for later increments.

PROJECT LIFE CYCLE AND EFFORT ESTIMATION Mental Delivery UNIT - II Dr.T.Logeswari Dept of CS

Communication and Collaboration: Effective communication is essential for project success. Project managers and team members need to communicate clearly and regularly to ensure everyone is on the same page. Collaboration fosters a positive team environment and helps in addressing issues and challenges collectively. Adaptability and Resilience: The ability to adapt to changes in requirements, technology, or project scope is crucial. Being resilient in the face of challenges helps the team overcome obstacles and continue progressing.

Leadership and Motivation: Strong leadership skills are vital for guiding the team and making decisions that align with project goals. Motivating the team and maintaining morale contribute to a positive work environment and can lead to higher productivity. Problem-Solving and Decision-Making: The project manager and team members should be adept at problem- solving and making informed decisions. Quick and effective decision- making is crucial to keep the project on track.

Time and Stress Management: Managing time effectively and handling stress are essential skills. Project managers need to create realistic timelines and help the team manage workload and stress levels. Continuous Learning: The software industry is dynamic, and staying updated on new technologies and methodologies is essential. Encouraging a culture of continuous learning helps the team adapt to changes and improve their skills.

PROJECT LIFE CYCLE AND EFFORT ESTIMATION Rapid Application Development UNIT - II Dr.T.Logeswari Dept of CS

RAD is a linear sequential software development process model that emphasizes a concise development cycle using an element-based construction approach. If the requirements are well understood and described, and the project scope is a constraint, the RAD process enables a development team to create a fully functional system within a concise time period. RAD (Rapid Application Development) is a concept that products can be developed faster and of higher quality through: Gathering requirements using workshops or focus groups Prototyping and early, reiterative user testing of designs The re-use of software components A rigidly paced schedule that refers design improvements to the next product version Less formality in reviews and other team communication

The various phases of RAD are as follows: Business Modelling: The information flow among business functions is defined by answering questions like what data drives the business process, what data is generated, who generates it, where does the information go, who process it and so on. Data Modelling: The data collected from business modeling is refined into a set of data objects (entities) that are needed to support the business. The attributes (character of each entity) are identified, and the relation between these data objects (entities) is defined. Process Modelling: The information object defined in the data modeling phase are transformed to achieve the data flow necessary to implement a business function. Processing descriptions are created for adding, modifying, deleting, or retrieving a data object. Application Generation: Automated tools are used to facilitate construction of the software; even they use the 4th GL techniques. Testing & Turnover: Many of the programming components have already been tested since RAD emphasis reuse. This reduces the overall testing time. But the new part must be tested, and all interfaces must be fully exercised.

PROJECT LIFE CYCLE AND EFFORT ESTIMATION Agile Methods UNIT - II Dr.T.Logeswari Dept of CS

What is Agile project management? Agile project management is a process for managing a project that involves constant collaboration and working in iterations. It works off the basis that a project can be continuously improved upon throughout its life cycle and adapt to changes quickly. What are the benefits of using Agile methodology? Agile is one of the most popular approaches to project management because it is flexible, it is adaptable to changes and it encourages customer feedback

Many teams embrace the Agile approach for the following reasons: Rapid progress: By effectively reducing the time it takes to complete various stages of a project, teams can elicit feedback in real time and produce working prototypes or demos throughout the process Customer and stakeholder alignment: Through focusing on customer concerns and stakeholder feedback, the Agile team is well positioned to produce results that satisfy the right people Continuous improvement: As an iterative approach, Agile project management allows teams to chip away at tasks until they reach the best end result

Types of Agile methodologies Agile project management is not a singular framework but an umbrella term that includes a wide range of methodologies, including Scrum, Kanban, Extreme Programming (XP), and the Adaptive Project Framework (APF). Scrum: It is ideal for projects with rapidly changing requirements, using short sprints. Kanban: It visualizes project progress and is great for tasks requiring steady output. Lean: It streamlines processes, eliminating waste for customer value. Extreme Programming (XP): It enhances software quality and responsiveness to customer satisfaction. Adaptive Project Framework (APF): Works well for projects with unclear details, as it adapts to constantly evolving client needs.

How to implement Agile methodology into projects 1. Choose the right Agile framework Your first priority is to select the right Agile framework for your team. Scrum: Principle-based project management Kanban: Visual workflows and processes Scrumban: Hybrid of Scrum and Kanban XP: Customer-focused product development APF: Versatile teamwork

2. Assemble your Agile team An Agile team isn t like any ordinary team. If you want to find success with any of the Agile methodologies, you need to build a team with clear roles and responsibilities and a culture of collaboration. 3. Plan the project Now that you ve selected one of the Agile methods and assembled your A-team, it s time to plan out your project. Meticulous planning is one of the secret ingredients of successful Agile project management. You might also draw up a product backlog during the planning phase, which is most common in software development projects. The product backlog allows you to assign a priority level to your tasks so everyone on the team knows what they should focus on.

4. Manage stakeholder expectations Before you get your project underway, it s important to check in with any key stakeholders to make sure you factor in their feedback. 5. Measure success Measuring project success is key to making meaningful progress with your Agile methodology of choice. By paying attention to what worked and what didn t during the project management process, you can extract key lessons to apply to future Agile projects. There are various ways to effectively track progress and measure success with Agile projects: Daily standups: Brief meetings to discuss obstacles and find solutions Sprint reviews: Informal sit-down meetings to present work and solicit team feedback Retrospectives: Reflections on past work to inspire and influence future progress

PROJECT LIFE CYCLE AND EFFORT ESTIMATION Extreme Programming UNIT - II Dr.T.Logeswari Dept of CS

Extreme programming (XP) is one of the most important software development frameworks of Agile models. It is used to improve software quality and responsiveness to customer requirements. Principles of Extreme programming: Coding: The concept of coding which is used in the XP model is slightly different from traditional coding. Here, the coding activity includes drawing diagrams (modeling) that will be transformed into code, scripting a web-based system, and choosing among several alternative solutions. Testing: The XP model gives high importance to testing and considers it to be the primary factor in developing fault-free software. Listening: The developers need to carefully listen to the customers if they have to develop good quality software. Sometimes programmers may not have the depth knowledge of the system to be developed. So, the programmers should understand properly the functionality of the system and they have to listen to the customers.

Designing: Without a proper design, a system implementation becomes too complex, and very difficult to understand the solution, thus making maintenance expensive. A good design results elimination of complex dependencies within a system. So, effective use of suitable design is emphasized. Feedback: One of the most important aspects of the XP model is to gain feedback to understand the exact customer needs. Frequent contact with the customer makes the development effective. Simplicity: The main principle of the XP model is to develop a simple system that will work efficiently in the present time, rather than trying to build something that would take time and may never be used. It focuses on some specific features that are immediately needed, rather than engaging time and effort on speculations of future requirements. Pair Programming: XP encourages pair programming where two developers work together at the same workstation. This approach helps in knowledge sharing, reduces errors, and improves code quality. Continuous Integration: In XP, developers integrate their code into a shared repository several times a day. This helps to detect and resolve integration issues early on in the development process.

Refactoring: XP encourages refactoring, which is the process of restructuring existing code to make it more efficient and maintainable. Refactoring helps to keep the codebase clean, organized, and easy to understand. Collective Code Ownership: In XP, there is no individual ownership of code. Instead, the entire team is responsible for the codebase. This approach ensures that all team members have a sense of ownership and responsibility towards the code. Planning Game: XP follows a planning game, where the customer and the development team collaborate to prioritize and plan development tasks. This approach helps to ensure that the team is working on the most important features and delivers value to the customer. On-site Customer: XP requires an on-site customer who works closely with the development team throughout the project. This approach helps to ensure that the customer s needs are understood and met, and also facilitates communication and feedback.

PROJECT LIFE CYCLE AND EFFORT ESTIMATION SCRUM UNIT - II Dr.T.Logeswari Dept of CS

Scrum is the type of Agile framework. It is a framework within which people can address complex adaptive problem while productivity and creativity of delivering product is at highest possible values. Scrum uses Iterative process. Silent features of Scrum are: Scrum is light-weighted framework Scrum emphasizes self-organization Scrum is simple to understand Scrum framework help the team to work together

Lifecycle of Scrum