أسس تطوير البرمجيات وتحسين الأنظمة

Software Evolution

• Software evolution is a continuous process of changing and adapting software systems.
• Changes happen due to new requirements, evolving business needs, and fixing errors.
• Software evolution is an unavoidable aspect of using software for a long time.
• Strategies for software evolution are important as the costs of changing the system may decrease with extra effort spent on developing a more maintainable system.

Topics Covered

• Evolution processes
• Software maintenance
• Legacy systems

Fundamental SW Process Activities

• Software Specification (Requirements Engineering): Defining the software to be produced and setting constraints.
• Software Design & Development: Creating and programming the software.
• Software Validation: Evaluating the software to make sure it meets the requirements.
• Software Evolution: Modifying the software to match with changing requirements.

Software Change

• Change is inevitable and occurs due to new requirements, altered business environments, bug fixes, and improvements.
• Maintaining existing systems is a major concern for companies.
• Change management is essential for ensuring that changes are implemented effectively and efficiently.

Importance of Evolution

• Organizations invest heavily in software systems, which are essential business assets.
• Maintaining and adapting these assets is vital for sustaining their value and meeting updated business requirements.
• Companies allocate a significant portion of their software budget to evolving existing systems rather than developing new ones.

Spiral Model of Development and Evolution

• A spiral model is a software development and evolution model.
• It has iterative phases that involve specification, implementation, operation, and validation.
• New versions are released and evaluated iteratively.

Evolution and Servicing

• Initial Development: The initial phase of software development.
• Evolution: The stage where the software is in operational use and evolves as new requirements are implemented.
• Servicing: The stage where modifications are made to the software (fixes only) for operational reasons.
• Phase-out: The point when no further modifications or changes are made to the software.

Evolution Processes

• Software type being maintained
• Development processes used
• Skills and experience of involved personnel
• Change proposals linked to components and enabling estimations.

The Software Evolution Process

• Change Requests: Initial requests for changes.
• Impact Analysis: Identifies the extent of changes.
• Release Planning
• Change Implementation: Implementing the changes.
• System Release: Deploying the updated software.
• Fault Repair: Processes of fixing problems.
• Platform Adaptation: Adjusting to new operating systems or environments.
• System Enhancement: Modifying the system for improvement.

Agile Methods and Evolution

• Agile approaches emphasize incremental development, making the transition from development to evolution seamless.
• Evolution is treated as a continuation of the development process through frequent releases
• Automated Regression Testing plays a key role in ensuring changes maintain the system's functionality.
• Changes can be documented and tracked through user stories.

Software Maintenance

• Modifying a program after deployment.
• Maintenance typically doesn't involve significant architectural changes.
• Maintenance often involves altering existing components or adding new ones.
• Three key maintenance types:
  • Fault repair
  • Environmental adaptation
  • Functionality addition

Lifetime Costs and Maintainability

• Total costs associated with a software system over its lifespan.
• Maintenance costs decrease when the system is designed for maintainability.
• Careful design reduces costs for understanding, analyzing, and testing the system, leading to greater efficiency.

Legacy Systems

• Legacy systems utilize older languages and technologies that are no longer commonly used in current development.
• They often involve outdated hardware such as mainframe computers
• Legacy systems may utilize old processes and procedures that have become outdated.
• Legacy systems are more complex socio-technical entities due to elements of hardware, software, libraries, and business processes involved.

Legacy System- Change or Replace

• Legacy system replacement is expensive and risky.
• Factors such as insufficient specifications, complex integration of system processes, undocumented rules, and budgets for software development are considered for decision process.
• Cost of using outdated programming languages and lacking documentation for the system.

Legacy System Management

• Organizations with legacy systems should develop a strategy for continued use.
• Choices include total system rewrite, refactoring, or adjusting the system with updates.