Chapter 2 of advanced Software Process.pdf
- 2. Software Engineering Process Models
- 3. Topics covered 2.1. Software process models 2.2. Process activities 2.3. Understand why processes should be organized 2.4. Understand how the Rational Unified Process integrates good software engineering
- 4. What is the Software Process Models? Software process models are structured approaches to software development that describe the stages of software creation, maintenance, and the relationships between these stages. The goal of a software process model is to guide controlling and coordinating the tasks to achieve the end product and objectives as effectively as possible. A software process model is a simplified representation of a software process in which each process model represents a process from a particular perspective and thus provides only partial information
- 5. Types of Software Process Models The waterfall model Incremental development Integration and configuration V-Model (Verification and Validation Model) Iterative Model Spiral Model Agile Methodologies RAD Model (Rapid Application Development) DevOp
- 6. 6 What is the Waterfall model? The waterfall approach was the first SDLC Model widely used in Software Engineering. The Waterfall Model is a sequential model that divides software development into pre-defined phases. The waterfall model is a breakdown of project activities into linear sequential phases, they are passed down onto each other, where each phase depends on the deliverables of the previous one and corresponds to a specialization of tasks
- 8. 8 Waterfall Model Phases 1. Requirements analysis and definition The system’s services, constraints, and goals are established by consultation with system users. 2. System and software design The systems design process allocates the requirements to either hardware or software systems by establishing an overall system architecture. 3. Implementation and unit testing testing involves verifying that each unit meets its specifications. 4. Integration and system testing The individual program units or programs are integrated and tested as a complete system to ensure that the software requirements have been met. 5. Operation and maintenance Maintenance involves correcting errors not discovered in earlier life cycle stages.
- 9. Waterfall Model Problems •Inflexibility: Difficult to accommodate changes once a phase is completed , that makes it difficult to respond to changing customer requirements. •Late Issue Detection: Problems are often discovered late in the development process. •Not Ideal for Complex Projects: Poor adaptability to projects with evolving requirements or high complexity. ■ This model is only appropriate when the requirements are well- understood and changes will be fairly limited during the design process. ■ The waterfall model is mostly used for large systems engineering projects where a system is developed at several sites.
- 10. Incremental Development The Incremental Model is a software development process that breaks down the system into smaller, manageable modules. Each module is developed and delivered incrementally, allowing parts of the system to be implemented and tested independently.
- 11. When We Use the Incremental Model? When the requirements are superior. A project has a lengthy development schedule. When the Software team is not very well-skilled or trained. When the customer demands a quick release of the product. Incremental development benefits 1. The cost of accommodating changing customer requirements is reduced. 2. It is easier to get customer feedback on the development work that has been done. 3. More rapid delivery and deployment of useful software to the customer is possible.
- 12. 12 Incremental Development Problems 1. Lack of process visibility 2. Systems are often poorly structured 3. Special skills (e.g. in languages for rapid prototyping) may be required. Applicability – For small or medium-size interactive systems; – For parts of large systems (e.g. the user interface); – For short-lifetime systems.
- 13. Integration and Configuration Model The Integration and Configuration Model focuses on assembling and configuring pre-existing software components and systems to meet specific user requirements. This model emphasizes integrating various components and systems, often sourced from different vendors or developed in-house, to create a cohesive software solution. is a model based on reuse, systems are adapted from existing components as much as possible. (sometimes called COTS -Commercial-off-the-shelf systems). Use Cases ■ Enterprise Systems: Ideal for integrating various enterprise applications (e.g., CRM, ERP) to create a unified solution. ■ Software Solutions with Pre-built Components: Suitable for projects that involve configuring and assembling pre-existing software components.
- 14. Strengths ■ Leveraging Existing Solutions: Utilizes existing components and systems, reducing development time and cost. ■ Flexibility: Allows for customization and configuration to meet specific user needs. ■ Reduced Development Effort: Minimizes the need for custom development by reusing and integrating existing solutions. ■ Faster Time to Market: Accelerates deployment by using pre-built components and systems. Weaknesses ■ Integration Complexity: Managing the integration of diverse components can be complex and challenging. ■ Dependency Management: Reliance on external components may introduce risks related to compatibility and updates. ■ Customization Limitations: May face limitations in customizing components if they are not designed for flexibility. ■ Potential for Overhead: Integration and configuration may introduce additional overhead and complexity.
- 15. Reuse-oriented Software Engineering Reuse-oriented software engineering (ROSE) is an approach that focuses on the systematic reuse of existing software components. It emphasizes the use of pre-existing software artifacts rather than developing new components from scratch, aiming to improve productivity, reduce costs, and enhance software quality. Stages : 1. Component analysis 2. Requirements modification. 3. System design. 4. implementation and integration Software 5. Maintenance
- 16. Cont…
- 17. Strengths ■ Cost Reduction: By reusing existing components, development costs can be significantly reduced. ■ Faster Development: Reusing components can speed up the development process since less time is spent creating new code. ■ Improved Quality: Reused components are often well-tested and reliable, which can lead to higher overall system quality. ■ Consistency: Reuse can lead to more consistent and standardized software systems. Weaknesses ■ Component Mismatch: Existing components may not fit perfectly with the new system’s requirements, leading to adaptation challenges. ■ Integration Complexity: Integrating disparate components can be complex and may require significant effort. ■ Dependency Management: Managing dependencies between reused components can be difficult, especially when components are updated or replaced. ■ Licensing and Legal Issues: Using third-party components may involve navigating complex licensing agreements and ensuring compliance with legal requirements.
- 18. V-Model (Verification and Validation Model) The V-Model, known as the Verification and Validation Model, is a software development process that emphasizes the relationship between each phase of the development life cycle and its corresponding testing phase. The V-Model is structured to ensure that each development activity is directly linked to a testing activity, promoting a thorough and systematic approach to quality Applications The V-Model is often used in safety-critical and mission-critical systems, such as aerospace, medical devices, and automotive systems. It is also used in projects where requirements are well understood and unlikely to change significantly during the development process
- 19. Strengths ■ Structured Approach: Provides a clear, structured process with well- defined phases and deliverables. ■ Early Detection of Defects: Emphasizes early development of test plans and testing activities, allowing for early defect detection and resolution. ■ Traceability: Ensures that each development activity is directly linked to a corresponding testing activity, improving traceability and accountability. Weaknesses ■ Inflexibility: The sequential nature of the V-Model makes it difficult to accommodate changes once the project is underway. ■ Time-Consuming: Detailed documentation and rigorous testing can be time-consuming and may slow down the development process. ■ Not Suitable for All Projects: Best suited for projects with well-defined
- 20. 20 Iteration Model ■ The Iteration Model is a software development approach where the project is broken down into segments called iterations. Iteration can be applied to any of the generic process models. Key Characteristics of the Iteration Model ■ Incremental Development: The software is developed in small, incremental releases, each adding more functionality until the complete system is built. ■ Repeated Cycles: Each iteration follows a similar cycle of activities (planning, design, implementation, testing, and evaluation). ■ Feedback Loop: After each iteration, feedback is gathered and used to improve the next iteration, ensuring that the final product better meets user needs and requirements. ■ Risk Management: Early iterations address high-risk elements, reducing uncertainty and potential issues later in the development process
- 21. 21 Spiral Development model The Spiral Model is a software development process that combines elements of both iterative development and the Waterfall model, emphasizing risk management and continuous refinement through repeated cycles called spirals. ■ Application •Large and Complex Projects: Projects with high levels of complexity and significant risk factors. •High-Risk Projects: Systems where failure could have severe consequences (e.g., aerospace, defense, medical systems). •Innovative Projects: Projects involving new technologies or innovative approaches where risks are not well understood.
- 22. 22 Spiral model of the software process
- 23. Strengths ■ Risk Reduction: Early and continuous risk identification and mitigation. ■ Flexibility: Can handle changes in requirements and adapt to new information. ■ User Involvement: Continuous feedback from stakeholders and users helps ensure the final product meets their needs. ■ Incremental Refinement: The system is developed and refined in incremental steps, allowing for continuous improvement. Weaknesses ■ Complexity: The model can be complex to manage and requires skilled project management. ■ Cost: Iterative risk analysis and prototyping can be expensive and time- consuming. ■ Expertise Required: Requires expertise in risk management and iterative
- 24. Plan-driven and Agile Processes Plan-driven processes are processes where all of the process activities are planned and progress is measured against this plan. In agile processes, planning is incremental and it is easier to change the process to reflect changing customer requirements. In practice, most practical processes include elements of both plan-driven and agile approaches.
- 25. 25 Process Activities? Real software processes are inter-leaved sequences of technical, collaborative, and managerial activities with the overall goal of specifying, designing, implementing, and testing a software system. The four basic process activities 1. Software requirement specifications 2. Software design and implementation 3. Software validation 4. Software evolution
- 26. The Requirements Engineering Process
- 27. 27 1. Software specification 1. Feasibility study: An estimate is made of whether the identified user needs may be satisfied, hardware technologies and cost-effective 2. Requirements elicitation and analysis This is the process of deriving the system requirements through observation of existing systems, discussions with potential users and procurers, task analysis, and so on. 3. Requirements specification is the activity of translating the information gathered during the analysis activity into a document 4. Requirements validation: this activity checks the requirements for realism, consistency, and completeness..
- 28. 28 2. Software design and implementation ■ Software design and implementation is the process of converting the system specification into an executable system. ■ Software design – Design a software structure that realises the specification; ■ Implementation – Translate this structure into an executable program;
- 30. 30 Design process activities 1. Architectural design, where you identify the overall structure of the system, relationships and how they are distributed. 3. Interface design, where you define the interfaces between system components. 4. Component selection and design, where you search for reusable components. If unavailable, you design how it will operate. Database design, where you design the system data structures and how these are to be represented in a database.
- 31. 31 The Software Design Process
- 32. 32 3. Software validation ■ Verification and validation (V & V) is intended to show that a system conforms to its specification and meets the requirements of the system customer. ■ Involves checking and review processes and system testing. ■ System testing involves executing the system with test cases that are derived from the specification of the real data to be processed by the system.
- 33. 33 Testing Stages 1. Component or unit testing – Individual components are tested independently; – Components may be functions or objects or coherent groupings of these entities. 2. System testing – Testing of the system as a whole. Testing of emergent properties is particularly important. 3. Acceptance testing – Testing with customer data to check that the system meets the customer’s needs.
- 35. 35 4. Software Evolution ■ Software is inherently flexible and can change. ■ As requirements change through changing business circumstances, the software that supports the business must also evolve and change. ■ Although there has been a demarcation between development and evolution (maintenance) this is increasingly irrelevant as fewer and fewer systems are completely new.
- 37. Understand why processes should be organized? •Efficiency and Productivity: Organized processes streamline tasks, leading to faster and more productive workflows. •Consistency and Quality: They ensure consistent performance and high- quality outcomes across tasks. •Resource and Risk Management: Proper organization optimizes resource use and helps manage risks effectively. •Communication and Collaboration: Clear processes improve teamwork and communication, aligning efforts towards common goals. •Adaptability and Continuous Improvement: Organized processes are easier to adapt and enhance, supporting growth and innovation.
- 38. 38 The Rational Unified Process ■ A modern process model derived from the work on the UML and associated process. ■ Normally described from 3 perspectives 1. A dynamic perspective, which shows the phases of the model over time 2. A static perspective, which shows the process activities that are enacted. 3. A practice perspective, which suggests good practices to be used during the process.
- 40. Chapter Assessment As a Software engineer, you are developing a system to SOBA Company which operates in several countries in the world. 1. Select the appropriate software process model that you will follow. 2. Explain what you selected it. 3. Also, list and explain the basic activities required to develop the Software System.
- 41. THANK YOU!