Software Processes Lecture 3

The Software Process

• Structured set of activities required for software system development.
• Key activities include:
  • Specification: Defining system requirements.
  • Design and Implementation: Organizing and creating the system.
  • Validation: Ensuring the system meets customer expectations.
  • Evolution: Adapting the system to changing customer needs.
• Software process models provide an abstract representation of these processes from various perspectives.

Software Process Descriptions

• Descriptions typically focus on activities like data modeling and user interface design along with their sequence.
• Elements included in process descriptions:
  • Products: Outcomes of activities.
  • Roles: Responsibilities of individuals involved.
  • Pre- and post-conditions: True statements before and after activities.

Plan-Driven and Agile Processes

• Plan-driven Processes: All activities are pre-planned, measuring progress against the plan.
• Agile Processes: Planning is iterative and adaptable, accommodating changing requirements.
• Most practical processes blend both approaches; no universally right or wrong processes exist.

Software Process Models

• Waterfall Model:
  • Plan-driven with distinct phases for specification and development.
• Incremental Development:
  • Interleaved phases of specification, development, and validation, adaptable to changes.
• Integration and Configuration:
  • Systems assembled from existing configurable components, can be plan-driven or agile.
• Most large systems use a combination of these models.

Waterfall Model Phases

• Phases include:
  • Requirements analysis and definition
  • System and software design
  • Implementation and unit testing
  • Integration and system testing
  • Operation and maintenance
• Main disadvantage is resistance to change once a phase is completed.

Waterfall Model Problems

• Inflexible stage partitioning complicates responses to customer requirement changes.
• Best for projects with well-understood and stable requirements.
• Commonly applied in large systems engineering projects with multiple sites due to its organized nature.

Incremental Development Benefits

• Reduced costs for adapting to changing customer requirements.
• Less re-analysis and documentation compared to waterfall model.
• Enhanced customer feedback opportunities through demonstrations.
• Faster delivery and deployment of actionable software benefits customers earlier.

Incremental Development Problems

• Lack of visibility in the process; challenges in measuring progress without regular deliverables.
• System structure may degrade with frequent increments without proper refactoring.
• Costs to incorporate further changes may rise as system complexity increases.

Integration and Configuration

• Based on reusing existing components or COTS (Commercial-off-the-shelf) systems.
• Configurable components adapt behavior to user requirements.
• Reuse is a standard approach for building business systems.

Types of Reusable Software

• Stand-alone application systems (COTS) for specific environments.
• Collections of objects developed as packages for integration with frameworks like .NET.
• Web services developed to standards for remote invocation.

Reuse-Oriented Software Engineering

• Key stages include:
  • Requirements specification
  • Software discovery and evaluation
  • Requirements refinement
  • Application system configuration
  • Component adaptation and integration

Advantages and Disadvantages of Reuse

• Advantages include reduced costs and risks from less new software development.
• Faster system delivery and deployment.
• Inevitably leads to requirement compromises; systems may not fully meet user needs.
• Potential loss of control over lifecycle of reused components.

Process Activities

• Real software processes are interleaved sequences of technical, collaborative, and managerial actions aimed at specifying, designing, implementing, and testing a system.
• Basic activities: specification, development, validation, evolution, organized differently based on the development approach (sequential in waterfall, interleaved in incremental).

This quiz covers the essential activities involved in software processes, including specification, design and implementation, validation, and evolution. Understanding these components is crucial for developing effective software systems. Test your knowledge and grasp the importance of each stage in the software development lifecycle.