Software Engineering and Problems with Solutions, Slides of Software Engineering

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Chapter 1

What is Software Engineering Shari L. Pfleeger Joanne M. Atlee 4 th Edition

Pfleeger and Atlee, Software Engineering: Theory and Practice Chapter 1. 2

Contents

1.1 What is Software Engineering? 1.2 How Successful Have We Been? 1.3 What Is Good Software? 1.4 Who Does Software Engineering? 1.5 A System Approach 1.6 An Engineering Approach 1.7 Members of the Development Team 1.8 How Has Software Engineering Changed?

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1.1 What is Software Engineering

Solving Problems

• Software products are large and complex
• Development requires analysis and synthesis
  • Analysis: decompose a large problem into smaller, understandable pieces - abstraction is the key
  • Synthesis: build (compose) a software from smaller building blocks - composition is challenging

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1.1 What is Software Engineering

Solving Problems (continued)

• The analysis process

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1.1 What is Software Engineering

Solving Problems (continued)

• Method: refers to a formal procedure; a formal “recipe” for accomplishing a goal that is typically independent of the tools used
• Tool: an instrument or automated system for accomplishing something in a better way
• Procedure: a combination of tools and techniques to produce a product
• Paradigm: philosophy or approach for building a product (e.g., OO vs structured approaches)

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1.1 What is Software Engineering

Where Does the Software Engineer Fit In?

• Computer science: focusing on computer hardware, compilers, operating systems, and programming languages
• Software engineering: a discipline that uses computer and software technologies as problem-solving tools

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1.2 How Successful Have We Been?

• Perform tasks more quickly and effectively
  • Word processing, spreadsheets, e-mail
• Support advances in medicine, agriculture, transportation, multimedia education, and most other industries
• Many good stories
• However, software is not without problems

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1.2 How Successful Have We Been?

Sidebar 1.1 Terminology for Describing Bugs

• A fault: occurs when a human makes a mistake, called an error, in performing some software activities
• A failure: is a departure from the system’s required behaviour

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1.3 What is Good Software?

• Good software engineering must always include a strategy for producing quality software
• Three ways of considering quality
  • The quality of the product
  • The quality of the process
  • The quality of the product in the context of the business environment

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1.3 What Is Good Software?

The Quality of the Product

• Users judge external characteristics
  • (e.g., correct functionality, number of failures, type of failures)
• Designers and maintainers judge internal characteristics (e.g., types of faults)
• Thus different stakeholders may have different criteria
• Need quality models to relate the user’s external view to developer’s internal view

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1.3 What Is Good Software?

The Quality of the Process

• Quality of the development and maintenance process is as important as the product quality
• The development process needs to be modeled
• Modeling will address questions such as
  • Where to find a particular kind of fault
  • How to find faults early
  • How to build in fault tolerance
  • What are alternative activities

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1.3 What Is Good Software?

The Quality of the Process (continued)

• Models for process improvement
  • SEI’s Capability Maturity Model (CMM)
  • ISO 9000
  • Software Process Improvement and Capability dEtermination (SPICE)

Pfleeger and Atlee, Software Engineering: Theory and Practice Chapter 1. 20 1.3 What Is Good Software? The Quality in the Context of the Business Environment

• Business value is as important as technical value
• Business value (in relationship to technical value) must be quantified
• A common approach: return on investment (ROI) – what is given up for other purposes
• ROI is interpreted in different terms: reducing costs, predicting savings, improving productivity, and costs (efforts and resources)

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1.4 Who Does Software Engineering?

• Customer: the company, organization, or person who pays for the software system
• Developer: the company, organization, or person who is building the software system
• User: the person or people who will actually use the system