Software Processes Overview

Software Processes

• Software processes are a structured set of activities required to develop a software system.
• Many different software processes exist, but all involve:
  • Specification: Defining what the system should do.
  • Design and implementation: Defining the system's organization and implementing it.
  • Validation: Checking that the system meets customer requirements.
  • Evolution: Adapting the system to changing customer needs.
• A software process model is an abstract representation of a process, presenting a description from a specific perspective.

Topics Covered

• Software process models
• Process activities
• Coping with change
• Process improvement

Plan-driven and Agile Processes

• Plan-driven processes: All process activities are planned in advance, and progress is measured against the plan.
• Agile processes: Planning is incremental, allowing for easier adjustments to reflect changing customer requirements.
• Most practical processes incorporate elements of both plan-driven and agile approaches. There is no one "right" process.

The Waterfall Model

• A plan-driven model with separate and distinct phases of specification and development.
• Phases:
  • Requirements definition
  • System and software design
  • Implementation and unit testing
  • Integration and system testing
  • Operation and maintenance
• Difficulty in accommodating changes after the process begins.

Waterfall Model Problems

• Inflexible partitioning into stages makes responding to changing customer requirements difficult.
• Works best when requirements are well-understood and changes are limited.
• Fewer business systems have stable requirements.
• Suitable for large projects with development at multiple sites, where the planned nature helps coordination.

Incremental Development

• Specification, development, and validation are interleaved.
• May be plan-driven or agile.
• Benefits:
  • Reduced cost of accommodating changing requirements.
  • Easier to get customer feedback.
  • Quicker delivery of usable software.
• Problems:
  • Process is not always visible to managers.
  • System structure can degrade over time if not carefully managed.

Integration and Configuration

• Relies on software reuse, integrating systems from existing components or commercial-off-the-shelf (COTS) systems.
• Configuring reused elements to adapt to user requirements is common.
• Reuse is the standard approach for many business systems. Detailed information on reuse is in Chapter 15 of the text.

Software Process Descriptions

• Process descriptions focus on activities like data modeling and user interface design, and the order of these activities.
• Descriptions should include:
  • Products: Outcomes of a process activity.
  • Roles: Responsibilities of people involved.
  • Pre- and post-conditions: Statements about the state of the process or product before and after an activity.

Key Process Stages (Reuse-Oriented)

• Requirements specification
• Software discovery and evaluation
• Requirements refinement
• Application system configuration
• Component adaptation and integration

Advantages/Disadvantages of Reuse-Oriented Development

• Advantages: reduced costs, faster delivery
• Disadvantages: compromises in requirements, loss of control over reused elements

Process Activities

• Real software processes are inter-leaved sequences of technical, collaborative, and managerial activities, aiming to specify, design, implement, and test a software system.
• Basic process activities (specification, development, validation, evolution) are organized differently in different processes (e.g., sequential in waterfall, interleaved in incremental).

The Requirements Engineering Process

• Elicitation and analysis, specification, validation, and documentation make up requirements engineering.
• Understanding user and system requirements is critical.

Software Specification

• Establishing required services and constraints for system operation and development.
• Includes requirements elicitation and analysis, specification, and validation.

Software Design and Implementation

• Converting system specifications into an executable system.
• Software design: Creating a software structure realizing the specification.
• Implementation: Translating the structure into an executable program.
• Activities are closely related and often interleaved.

Design Activities

• Architectural design: Identifying overall system structure, components, relationships, and distribution.
• Database design: Designing data structures and their representation in a database.
• Interface design: Defining interfaces between system components.
• Component selection and design: Seeking reusable components; designing custom if necessary.

System Implementation

• Implementing software either through program development or configuration.
• Design and implementation activities are often interleaved.
• Programming is often an individual activity without a strict standard process.
• Debugging is essential for identifying and fixing program errors.

Software Validation

• Verifying and validating (V&V) that a system meets its specification and user requirements.
• Includes checking and review processes, along with testing.
• System testing executes the system with test cases based on specifications and real data.
• Testing is the most common V&V activity.

Stages of Testing

• Component testing: Testing individual components (e.g., functions, objects) in isolation.
• System testing: Testing the entire system as a whole.
• Customer testing: Testing with real customer data to ensure the system meets customer needs.

Testing Phases in a Plan-Driven Process (V-Model)

• A detailed view of testing phases in a plan-driven process.

Software Evolution

• Software is adaptable and must change to meet evolving business requirements.
• Development and evolution (maintenance) are merging, as few systems are completely new.

System Evolution

• A process for assessing, proposing changes, and modifying existing software systems to adapt to new needs.

Coping with Change

• Change is inevitable in software projects.
• Business changes, new technologies, and platform changes lead to evolving requirements and adaptations.
• Change leads to rework of existing processes.

Reducing Costs of Rework (Coping with Change)

• Change anticipation: Including activities to predict potential changes before significant rework becomes necessary. (E.g., prototyping)
• Change tolerance: Designing processes to accommodate changes at low cost without disrupting the entire system (e.g., incremental development).

Coping with Changing Requirements

• System prototyping: Quickly developing a version of the system to test requirements and feasibility of design decisions
• Incremental delivery: Delivering system increments for customer feedback and evaluation.

Software Prototyping

• Prototypes are initial versions of a system used to demonstrate concepts and test design options.
• Can help requirements elicitation and validation.

Benefits of Prototyping

• Improves system usability.
• Matches user needs closer.
• Improves design quality.
• Improves maintainability.
• Reduces development effort.
• Process of Prototype Development: Establishing objectives, Defining functionality, Developing prototype, Evaluating prototype

Prototype Development

• Can use rapid prototyping languages/tools.
• May leave out non-critical features, focusing on functional areas.
• Error checking may not be included in initial versions.

Incremental Delivery

• Delivering the system in a series of increments, each with prioritized features.
• User requirements are incorporated into early increments.
• Requirements for later increments can evolve.
• This approach is very useful during iterative development and is very common in modern software development processes.

Incremental Delivery Advantages

• Early value delivered to the customer.
• Prototyping for eliciting requirements for future increments.
• Reduces risk of overall project failure.
• Highest priority features receive most testing

Incremental Delivery Problems

• Defining basic facilities used by different system increments can be challenging.
• Defining full requirements before development is difficult.
• Procurement issues can arise in business contracts.

Throw-Away Prototypes

• Prototypes serve as a tool in the development process but are not intended for ongoing use.
• They might not meet the non-functional requirements of a production system, are usually not documented, and may contain many errors.

Process Improvement

• Many companies use process improvement to enhance software quality and reduce costs.
• Process improvement involves understanding existing processes and adjusting them to enhance quality and reduce development time.

Approaches to Improvement

• Process maturity approach: Focuses on improved process management and software engineering practices.
• Agile approach: Iterative development to streamline overhead and respond quickly to changes.

The Process Improvement Cycle

• A cyclical process: measure, analyze, change, and repeat to continuously improve.

Process Improvement Activities

• Process measurement: Collecting data on existing processes or products.
• Process analysis: Identifying process weaknesses and bottlenecks, and creating process models or maps.
• Process change: Implementing measures to address identified weaknesses and improve efficiency.

Process Measurement

• Gathering quantitative data on software processes and products.
• Measurements are used for assessing process improvements and should align with overall organizational objectives.

Process Metrics

• Examples of process metrics:
  • Time taken for activities
  • Resources required
  • Number of errors

Capability Maturity Levels

• A framework for describing the maturity levels of software processes.
• Levels: Initial, Repeatable, Defined, Managed, Optimizing.

The SEI Capability Maturity Model

• A model that identifies maturity levels of a software process.
• Levels: Initial, Repeatable, Defined, Managed, Optimizing. The higher the level achieved, the better the software development practices.

Key Points Summary

• Software processes are crucial activities in software development.
• Models describe the structure. Requirements engineering clarifies needs, validation checks adherence.
• Design and implementation turns specifications into executable systems.
• Validation and testing are critical to ensure quality. Evolution manages changes throughout the life cycle.
• Iterative/Incremental development enables flexible adaptation to evolving requirements and change.
• Continuous improvement (process improvement activities) should be ongoing.

This quiz covers the essential activities and models that define software processes, including specification, design, validation, and evolution. Explore the differences between plan-driven and agile processes and understand how to cope with change and improve processes effectively.