Introduction of Software Engineering

Chapter 1
• Software & Software Engineering
These slides are designed and adapted from slides provided by Software Engineering: A Practitioner’s Approach, 7/e
(McGraw-Hill 2009) by Roger Pressman and Software Engineering 9/e Addison Wesley 2011 by Ian Sommerville
1
Software Engineering: A Practitioner’s Approach, 7/e
by Roger S. Pressman
Slides copyright © 1996, 2001, 2005, 2009 by Roger S. Pressman
Software Engineering 9/e
By Ian Sommerville
CS435: Introduction to Software Engineering
Dr. M. Zhu

FAQ about software engineering
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Question Answer
What is software? Computer programs, data structures and associated
documentation. Software products may be developed for
a particular customer or may be developed for a general
market.
What are the attributes of good software? Good software should deliver the required functionality
and performance to the user and should be
maintainable, dependable and usable.
What is software engineering? Software engineering is an engineering discipline that is
concerned with all aspects of software production.
What is the difference between software
engineering and computer science?
Computer science focuses on theory and fundamentals;
software engineering is concerned with the practicalities
of developing and delivering useful software.
What is the difference between software
engineering and system engineering?
System engineering is concerned with all aspects of
computer-based systems development including
hardware, software and process engineering. Software
engineering is part of this more general process.

Essential attributes of good software
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Product characteristic Description
Maintainability Software should be written in such a way so that it can evolve to
meet the changing needs of customers. This is a critical attribute
because software change is an inevitable requirement of a
changing business environment.
Dependability and
security
Software dependability includes a range of characteristics
including reliability, security and safety. Dependable software
should not cause physical or economic damage in the event of
system failure. Malicious users should not be able to access or
damage the system.
Efficiency Software should not make wasteful use of system resources such
as memory and processor cycles. Efficiency therefore includes
responsiveness, processing time, memory utilisation, etc.
Acceptability Software must be acceptable to the type of users for which it is
designed. This means that it must be understandable, usable and
compatible with other systems that they use.

A Layered Technology
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Software Engineering
a “quality” focus
process model
methods
tools
 Any engineering approach must rest on organizational commitment to quality which fosters a
continuous process improvement culture.
 Process layer as the foundation defines a framework with activities for effective delivery of
software engineering technology. Establish the context where products (model, data, report, and
forms) are produced, milestone are established, quality is ensured and change is managed.
 Method provides technical how-to’s for building software. It encompasses many tasks
including communication, requirement analysis, design modeling, program construction, testing
and support.
 Tools provide automated or semi-automated support for the process and methods.

Software Process
• A process is a collection of activities, actions and tasks
that are performed when some work product is to be
created. It is not a rigid prescription for how to build
computer software. Rather, it is an adaptable approach
that enables the people doing the work to pick and choose
the appropriate set of work actions and tasks.
• Purpose of process is to deliver software in a timely
manner and with sufficient quality to satisfy those who
have sponsored its creation and those who will use it.
5

Five Activities of a Generic
Process framework
• Communication: communicate with customer to understand objectives and gather
requirements
• Planning: creates a “map” defines the work by describing the tasks, risks and
resources, work products and work schedule.
• Modeling: Create a “sketch”, what it looks like architecturally, how the
constituent parts fit together and other characteristics.
• Construction: code generation and the testing.
• Deployment: Delivered to the customer who evaluates the products and provides
feedback based on the evaluation.
• These five framework activities can be used to all software development
regardless of the application domain, size of the project, complexity of the efforts
etc, though the details will be different in each case.
• For many software projects, these framework activities are applied iteratively as
a project progresses. Each iteration produces a software increment that provides a
subset of overall software features and functionality.
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Umbrella Activities
Complement the five process framework activities and help team manage and control
progress, quality, change, and risk.
• Software project tracking and control: assess progress against the plan and take
actions to maintain the schedule.
• Risk management: assesses risks that may affect the outcome and quality.
• Software quality assurance: defines and conduct activities to ensure quality.
• Technical reviews: assesses work products to uncover and remove errors before
going to the next activity.
• Measurement: define and collects process, project, and product measures to ensure
stakeholder’s needs are met.
• Software configuration management: manage the effects of change throughout the
software process.
• Reusability management: defines criteria for work product reuse and establishes
mechanism to achieve reusable components.
• Work product preparation and production: create work products such as models,
documents, logs, forms and lists.
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The Essence of Practice
• How does the practice of software engineering fit in the
process activities mentioned above? Namely,
communication, planning, modeling, construction and
deployment.
• George Polya outlines the essence of problem solving,
suggests:
1.Understand the problem (communication and analysis).
2.Plan a solution (modeling and software design).
3.Carry out the plan (code generation).
4.Examine the result for accuracy (testing and quality
assurance).
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Understand the Problem
• Who has a stake in the solution to the problem?
That is, who are the stakeholders?
• What are the unknowns? What data, functions, and
features are required to properly solve the problem?
• Can the problem be compartmentalized? Is it
possible to represent smaller problems that may be
easier to understand?
• Can the problem be represented graphically? Can
an analysis model be created?
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Plan the Solution
• Have you seen similar problems before? Are there patterns
that are recognizable in a potential solution? Is there existing
software that implements the data, functions, and features that
are required?
• Has a similar problem been solved? If so, are elements of the
solution reusable?
• Can subproblems be defined? If so, are solutions readily
apparent for the subproblems?
• Can you represent a solution in a manner that leads to
effective implementation? Can a design model be created?
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Carry Out the Plan
• Does the solutions conform to the plan? Is source
code traceable to the design model?
• Is each component part of the solution provably
correct? Has the design and code been reviewed, or
better, have correctness proofs been applied to
algorithm?
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Examine the Result
• Is it possible to test each component part of the
solution? Has a reasonable testing strategy been
implemented?
• Does the solution produce results that conform to
the data, functions, and features that are required?
Has the software been validated against all
stakeholder requirements?
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Introduction of Software Engineering

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