Software Engineering
Software Engineering
Contents
OVERVIEW: Introduction; Software engineering ethics; Software process models; Process
activities; Coping with change; Agile software development: Agile methods; Plan-driven and agile
development.
REQUIREMENTS ENGINEERING: Functional and non-functional requirements; Software
requirements document; Requirement’s specification; Requirements engineering processes;
Requirement’s elicitation and analysis; Requirement’s validation; Requirements management.
SYSTEM MODELING: Context models; Interaction models- Use case modeling, Sequence
diagrams; Structural models- Class diagrams, Generalization, Aggregation; Behavioral Models-
Data-driven modeling, Event-driven modeling; Model-driven engineering.
ARCHITECTURAL DESIGN: Architectural design decisions; Architectural views; Architectural
patterns- Layered architecture, Repository architecture, Client–server architecture Pipe and filter
architecture.
DESIGN AND IMPLEMENTATION: Object-oriented design using the UML- System context and
interactions, Architectural design, Object class identification, Design models, Interface specification;
Design patterns; Implementation issues.
SOFTWARE TESTING: Development testing- Unit testing, Choosing unit test cases, Component
testing, System testing. Test-driven development; Release testing; User testing- Alpha, Beta,
Acceptance testing.
Dr. K. Adisesha 1
,Software Engineering
Software Engineering
Software and software systems are everywhere. The economies of ALL developed nations are
dependent on software. More and more systems are software controlled. Software engineering is
concerned with theories, methods and tools for professional software development. Expenditure on
software represents a significant fraction of GNP in all developed countries.
Software Engineering
Definition by IEEE (Institute of Electrical and Electronics Engineers): The application of
systematic, disciplined, quantifiable approach to the development, operation, maintenance of software
that is the application of engineering to the software.
Applying software engineering principles helps address the two main factors of software failures:
➢ Increasing demands: As new software engineering techniques help us to build larger, more
complex systems, the demands change. Systems have to be built and delivered more quickly;
larger, even more complex systems are required; systems have to have new capabilities that
were previously thought to be impossible.
➢ Low expectations: It is relatively easy to write computer programs without using software
engineering methods and techniques. Computer programming is NOT software engineering.
Goals of Software Engineering
➢ To improve the quality of the software product
➢ To increase productivity and
➢ To give job satisfaction to the Software engineers.
Key Challenges of Software Engineering
➢ The legacy challenge: The challenging method of maintaining and updating the software in
such a way that high costs are avoided and essential business services continue to be delivered.
➢ The Heterogeneity challenge: Systems are required to operate as distributed systems across
networks. The challenge of developing techniques to build dependable software which is
flexible to cope with is called heterogeneity.
➢ The delivery challenge: A challenge of shortening delivery time for large and complex
systems without compromising system quality.
Software Product
Software products are software systems that are delivered to a customer with documentation which
describes how to install and use this system.
Software products may be classified into two types.
Generic Products
➢ These products are developed in organizations and sold in the open market to any customer
who is able to buy them.
➢ These are stand-alone systems; the target is generally how many copies are being sold.
➢ These products are developed for anonymous customers
Dr. K. Adisesha 2
,Software Engineering
➢ Example: Operating Systems, Word Processors, drawing packages etc
Bespoke (Customized) Products
➢ These products are developed for a single customer according to their specification.
➢ These are customized products
➢ These products are designed as per customer’s requirement by software contractor.
➢ Example: Payroll system, Inventory system, Air traffic control system etc
Essential attributes of good software
➢ 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.
Software engineering: a definition
Software engineering is an engineering discipline that is concerned with all aspects of software
production from the early stages of system specification through to maintaining the system after it has
gone into use. It is an engineering discipline because it uses appropriate theories and methods to solve
problems bearing in mind organizational and financial constraints. Software engineering focuses on all
aspects of software production and not just on the technical process of development; it includes project
management and the development of tools, methods etc. to support software production.
It is usually cheaper, in the long run, to use software engineering methods and techniques for software
systems rather than just write the programs as if it was a personal programming project. For most types
of system, the majority of costs are the costs of changing the software after it has gone into use.
Any software process includes four types of activities:
➢ Software specification, where customers and engineers define the software that is to be
produced and the constraints on its operation.
➢ Software development, where the software is designed and programmed.
➢ Software validation, where the software is checked to ensure that it is what the customer
requires.
➢ Software evolution, where the software is modified to reflect changing customer and market
requirements.
General issues affecting most software
Dr. K. Adisesha 3
, Software Engineering
➢ Heterogeneity: Increasingly, systems are required to operate as distributed systems across
networks that include different types of computer and mobile devices.
➢ Business and social change: Business and society are changing incredibly quickly as
emerging economies develop and new technologies become available. They need to be able to
change their existing software and to rapidly develop new software.
➢ Security and trust: As software is intertwined with all aspects of our lives, it is essential that
we can trust that software.
Software engineering fundamentals
These software engineering fundamentals that apply to all types of software system:
Software process: Systems should be developed using a managed and understood development
process. The organization developing the software should plan the development process and have clear
ideas of what will be produced and when it will be completed. Of course, different processes are used
for different types of software.
Focus on reliability: Dependability and performance are important for all types of systems. Software
should behave as expected, without failures and should be available for use when it is required. It
should be safe in its operation and, as far as possible, should be secure against external attack. The
system should perform efficiently and should not waste resources.
Importance of requirements: Understanding and managing the software specification and
requirements (what the software should do) are important. You have to know what different customers
and users of the system expect from it and you have to manage their expectations so that a useful
system can be delivered within budget and to schedule.
Leverage software reuse: You should make as effective use as possible of existing resources. This
means that, where appropriate, you should reuse software that has already been developed rather than
write new software.
Software engineering ethics: Some issues of professional responsibility:
Confidentiality: You should normally respect the confidentiality of your employers or clients
irrespective of whether or not a formal confidentiality agreement has been signed.
Competence: You should not misrepresent your level of competence. You should not knowingly
accept work that is outside your competence.
Intellectual property rights: You should be aware of local laws governing the use of intellectual
property such as patents and copyright. You should be careful to ensure that the intellectual property
of employers and clients is protected.
Computer misuse: You should not use your technical skills to misuse other people's computers.
Computer misuse ranges from relatively trivial (game playing on an employer's machine, say) to
extremely serious (dissemination of viruses or other malware).
Dr. K. Adisesha 4
Software Engineering
Contents
OVERVIEW: Introduction; Software engineering ethics; Software process models; Process
activities; Coping with change; Agile software development: Agile methods; Plan-driven and agile
development.
REQUIREMENTS ENGINEERING: Functional and non-functional requirements; Software
requirements document; Requirement’s specification; Requirements engineering processes;
Requirement’s elicitation and analysis; Requirement’s validation; Requirements management.
SYSTEM MODELING: Context models; Interaction models- Use case modeling, Sequence
diagrams; Structural models- Class diagrams, Generalization, Aggregation; Behavioral Models-
Data-driven modeling, Event-driven modeling; Model-driven engineering.
ARCHITECTURAL DESIGN: Architectural design decisions; Architectural views; Architectural
patterns- Layered architecture, Repository architecture, Client–server architecture Pipe and filter
architecture.
DESIGN AND IMPLEMENTATION: Object-oriented design using the UML- System context and
interactions, Architectural design, Object class identification, Design models, Interface specification;
Design patterns; Implementation issues.
SOFTWARE TESTING: Development testing- Unit testing, Choosing unit test cases, Component
testing, System testing. Test-driven development; Release testing; User testing- Alpha, Beta,
Acceptance testing.
Dr. K. Adisesha 1
,Software Engineering
Software Engineering
Software and software systems are everywhere. The economies of ALL developed nations are
dependent on software. More and more systems are software controlled. Software engineering is
concerned with theories, methods and tools for professional software development. Expenditure on
software represents a significant fraction of GNP in all developed countries.
Software Engineering
Definition by IEEE (Institute of Electrical and Electronics Engineers): The application of
systematic, disciplined, quantifiable approach to the development, operation, maintenance of software
that is the application of engineering to the software.
Applying software engineering principles helps address the two main factors of software failures:
➢ Increasing demands: As new software engineering techniques help us to build larger, more
complex systems, the demands change. Systems have to be built and delivered more quickly;
larger, even more complex systems are required; systems have to have new capabilities that
were previously thought to be impossible.
➢ Low expectations: It is relatively easy to write computer programs without using software
engineering methods and techniques. Computer programming is NOT software engineering.
Goals of Software Engineering
➢ To improve the quality of the software product
➢ To increase productivity and
➢ To give job satisfaction to the Software engineers.
Key Challenges of Software Engineering
➢ The legacy challenge: The challenging method of maintaining and updating the software in
such a way that high costs are avoided and essential business services continue to be delivered.
➢ The Heterogeneity challenge: Systems are required to operate as distributed systems across
networks. The challenge of developing techniques to build dependable software which is
flexible to cope with is called heterogeneity.
➢ The delivery challenge: A challenge of shortening delivery time for large and complex
systems without compromising system quality.
Software Product
Software products are software systems that are delivered to a customer with documentation which
describes how to install and use this system.
Software products may be classified into two types.
Generic Products
➢ These products are developed in organizations and sold in the open market to any customer
who is able to buy them.
➢ These are stand-alone systems; the target is generally how many copies are being sold.
➢ These products are developed for anonymous customers
Dr. K. Adisesha 2
,Software Engineering
➢ Example: Operating Systems, Word Processors, drawing packages etc
Bespoke (Customized) Products
➢ These products are developed for a single customer according to their specification.
➢ These are customized products
➢ These products are designed as per customer’s requirement by software contractor.
➢ Example: Payroll system, Inventory system, Air traffic control system etc
Essential attributes of good software
➢ 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.
Software engineering: a definition
Software engineering is an engineering discipline that is concerned with all aspects of software
production from the early stages of system specification through to maintaining the system after it has
gone into use. It is an engineering discipline because it uses appropriate theories and methods to solve
problems bearing in mind organizational and financial constraints. Software engineering focuses on all
aspects of software production and not just on the technical process of development; it includes project
management and the development of tools, methods etc. to support software production.
It is usually cheaper, in the long run, to use software engineering methods and techniques for software
systems rather than just write the programs as if it was a personal programming project. For most types
of system, the majority of costs are the costs of changing the software after it has gone into use.
Any software process includes four types of activities:
➢ Software specification, where customers and engineers define the software that is to be
produced and the constraints on its operation.
➢ Software development, where the software is designed and programmed.
➢ Software validation, where the software is checked to ensure that it is what the customer
requires.
➢ Software evolution, where the software is modified to reflect changing customer and market
requirements.
General issues affecting most software
Dr. K. Adisesha 3
, Software Engineering
➢ Heterogeneity: Increasingly, systems are required to operate as distributed systems across
networks that include different types of computer and mobile devices.
➢ Business and social change: Business and society are changing incredibly quickly as
emerging economies develop and new technologies become available. They need to be able to
change their existing software and to rapidly develop new software.
➢ Security and trust: As software is intertwined with all aspects of our lives, it is essential that
we can trust that software.
Software engineering fundamentals
These software engineering fundamentals that apply to all types of software system:
Software process: Systems should be developed using a managed and understood development
process. The organization developing the software should plan the development process and have clear
ideas of what will be produced and when it will be completed. Of course, different processes are used
for different types of software.
Focus on reliability: Dependability and performance are important for all types of systems. Software
should behave as expected, without failures and should be available for use when it is required. It
should be safe in its operation and, as far as possible, should be secure against external attack. The
system should perform efficiently and should not waste resources.
Importance of requirements: Understanding and managing the software specification and
requirements (what the software should do) are important. You have to know what different customers
and users of the system expect from it and you have to manage their expectations so that a useful
system can be delivered within budget and to schedule.
Leverage software reuse: You should make as effective use as possible of existing resources. This
means that, where appropriate, you should reuse software that has already been developed rather than
write new software.
Software engineering ethics: Some issues of professional responsibility:
Confidentiality: You should normally respect the confidentiality of your employers or clients
irrespective of whether or not a formal confidentiality agreement has been signed.
Competence: You should not misrepresent your level of competence. You should not knowingly
accept work that is outside your competence.
Intellectual property rights: You should be aware of local laws governing the use of intellectual
property such as patents and copyright. You should be careful to ensure that the intellectual property
of employers and clients is protected.
Computer misuse: You should not use your technical skills to misuse other people's computers.
Computer misuse ranges from relatively trivial (game playing on an employer's machine, say) to
extremely serious (dissemination of viruses or other malware).
Dr. K. Adisesha 4
