Lecture 1: Software Engineering: Introduction

1
Lecture 1 Software Engineering Introduction

• Dr Valentina Plekhanova
• University of Sunderland, UK

http//www.cet.sunderland.ac.uk/cs0vpl/SE-Com185.
htm
2
Background and Definitions

• What is Software?
•  Could say software is
• instructions (programs) to provide desired
  function and performance
• data structures that enable the program to
  manipulate information
• documents that describe the operation and use of
  the programs.

3
Background and Definitions

• Can also look at software characteristics and
  application domains to get a better idea of what
  software is
•  
• Software is more than code!

4
Background and Definitions

• Software any computer instructions written to be
  executed on hardware, including operating
  systems, utility programs, and application
  programs.
• Academic Press Dictionary of Science and
  Technology

5
Software Applications Pressman, R.S., 2000

• The characteristics of software vary with the
• application domain. Some examples
• Real-time Software
• Business Software
• Engineering and Scientific Software
• Embedded Software
• Personal Computer (consumer) software
• AI Software
• ..

6
Software Applications

• The methods, techniques and tools for software
  development can vary considerably between
  application domains.

7
What is ? Sommerville

• What is Engineering?
• Engineers try to discover the problems and
  find/develop apply appropriate theories,
  methods, and tools to the solutions to these
  problems.
• What is System Engineering?
• (Computer-based) System engineering is concerned
  with hardware development and evolution of
  complex systems policy, process design and
  system deployment as well as software engineering
  
• What is Software Engineering?

8
An Engineering Approach considers the following
Pressman, R.S., 2000

• What is the problem to be solved?
• What are the characteristics of the entity that
  are used to solve the problem?
• How will the entity (and solution) be realised?
• What approach will be used to uncover errors in
  the design and construction of the entity?
• How will the entity be maintained - corrections,
  adaptations and enhancements requested by users
  of the entity?

9
The Software Crisis

• The development of software engineering tools and
  methods began in the late 1960s, largely in
  response to what many authors have termed the
  software crisis.
• The "software crisis" refers to the inability of
  developers to deliver reliable software, within
  cost and schedule.

10
The Software Crisis

• This crisis arose from the rapid increase in the
  size and complexity of computer applications.
• Systems became much too large and complicated to
  be performed by one individual or two people
  instead, large project teams were required.

11
Software Characteristics

• Software is logical rather then physical
  (though there are physical representations of the
  software).
• Software is developed or engineered, it is not
  manufactured in the classical sense.
• Nearly all the software costs are in the
  engineering, rather than manufacture.
• Classical project management for engineering
  projects do not map directly to software projects.

12
Software Characteristics

• Lack of visibility of software.
• Complexity of software projects not linear with
  size - projects do not scale up well as larger
  projects much more complex.
• Software subject to frequent change to
  requirements.
• Lack of good spatial representations for
  software.
• Most software is custom built, rather than being
  assembled from standard components.

13
Software Characteristics

• Ideal does not occur because
• Software is always subject to changes in
  requirements or the operating environment.
• Fixing errors in software is not the same as
  fixing errors in hardware. Dont just replace
  component, but change the system. This can
  introduce new errors.

14
Software Myths Pressman, R.S., 2000

• Myths or attitudes to software development
  include
• Management Myths, e.g.
• Have standards and procedures for building
  software - what more do we need?
• My programmers have state of the art s/w
  development tools - we buy them the newest
  computers.   

15
Software Myths Pressman, R.S., 2000

• If we get behind schedule, we can add more
  programmers and catch up.
• A general statement of objectives is sufficient
  to begin writing programs - we can fill in the
  details later.

16
Software Myths Pressman, R.S., 2000

• Customer Myths, e.g.
• Project requirements continually change, but
  change can be easily accommodated because
  software is flexible.
• Practitioner's Myths, e.g.
• Once we write the program and get it to work, our
  job is done.
• Until I get the program running, I really have no
  way of assessing its quality.
• The only delivery for a successful project is the
  working program.

17
Software Engineering Definitions

• There are a large number of definitions of
• software engineering
• The establishment and use of sound engineering
  principles in order to obtain, economically,
  software that is reliable and works efficiently
  on real machines Bauer, 1972

18
Software Engineering Definitions

• The process of creating software systems (using)
  techniques that reduce high software cost and
  complexity while increasing reliability and
  modifiability Ramamoorthy and Siyan, 1983

19
Software Engineering Definitions

• The technological and managerial discipline
  concerned with systematic production and
  maintenance of software products that are
  developed on time and within cost estimates
  Fairley, 1984

20
Software Engineering Definitions

• Software engineering the application of the
  techniques and disciplines of engineering to the
  development of high-quality, large-scale software
  systems includes controlled design, structured
  program methodology, productivity aids, and
  project management tools.
• Academic Press Dictionary of Science and
  Technology

21
Software Engineering Definitions

• We consider software engineering as the
  application of mathematical techniques and
  rigorous engineering methods to software
  development.
• We also need to support synthesis of formal
  methods and heuristic approaches to engineering
  tasks, which ensures managerial support for the
  evaluation, comparison, analysis, evolution and
  improvement of resources.
• We need to use heuristic approaches where
  heuristics can be defined as reasonable/effective
  and supportive tool for decision making.
  Plekhanova, 1997

22
Software Engineering Definitions

• Software Engineering A systematic approach to
  the analysis, design, implementation and
  maintenance of software. It usually involves the
  use of CASE tools. There are various models of
  the software life-cycle, and many methodologies
  for the different phases. http//sting.web.cern.ch
  /sting/glossary.html

23
Keywords

• Reason
• reliability,
• efficiency,
• high-quality,
• software/systems,
• reduce cost/time,
• increase productivity.

24
Keywords

• Application of methods/techniques/tools the
  techniques and disciplines of engineering
  mathematical techniques and rigorous engineering
  methods synthesis/integration of formal methods
  and heuristic approaches to engineering tasks,
  CASE tools

25
Common factors to these definitions include

• Software Engineering is concerned with software
  systems built by teams rather than individuals.
• Engineering principles are used in the software
  development process.
• Software Engineering involves both technical and
  non-technical considerations.

26
Generic View of Software Engineering

• Engineering is the analysis, design,
  construction, verification, and management of
  technical (and social) entities.
•  

27
Three generic phasesPressman, R.S., 2000

• Definition phase - focus on what
• Systems engineering
• Project planning/scheduling
• Requirements analysis.

28
Three generic phases

• Development phase - focus on how
• Software Design
• Implementation (Code generation)
• Testing.

29
Three generic phases

• Maintenance phase - focus on change
• modification
• Correction
• Adaptation
• Enhancement
• Prevention.

30
Week 4 24.02.03- 28.02.03

• Project Control Session
• Tutorial Time 10 minutes for each Team
• Project Team will present project file Schedule,
  any project documentation.
• Students will describe where they are in the
  project and any problems encountered.
• During the discussion reviewers will ask to see
  evidence of deliverables for any tasks that are
  complete to determine whether they have in fact
  been done.