1. I n t r o d u c t i o n to S o f t w a r e En g i n e e r i n g
C h a p t e r 1
I n t r o d u c t i o n to S o f t w a r e En g i n e e r i n g
Dr.Doaa Sami
Modified from Sommerville’s originals

2. Objectives  To introduce software engineering2
 To introduce software engineering
 To explain the importance of software engineering
 To give the basic software properties
 To introduce ethical and professional issues

3. Software List as many as you can …3
Think about all the devices and systems that you encounter in your everyday life which have software controlling them
List as many as you can …
Virtually all countries depend on computer

4. Introduction dependent on software.4
 The economies of ALL developed nations are
dependent on software.
 More and more life systems such as hospitals,
universities and ministries are software
controlled.
 More and more, individuals and society rely on
advanced software systems. We need to be able
to produce reliable and trustworthy systems
economically and quickly.

5. Software Crisis r9cYp3tTE Example 1 :Airplane Explosion5
Example 1 :Airplane Explosion
 European Space Agency spent 10 years
and $7 billion to produce Ariane 5.
 Crash after 36.7 seconds .
 Caused by an overflow error. Trying to
store a 64-bit number into a 16-bit space.
 Watch the video
r9cYp3tTE

6. Software Crisis Example 2: London Ambulance Service6
Example 2: London Ambulance Service
 Considered the largest ambulance service in the world.
 It was unable to keep track of the ambulances and their statuses. Sending multiple units to some locations and no units to other locations.
 Generates many exceptions messages.
 Overloaded problem  46 deaths.

7. Software Definition Computer Programs.7
 The term “Software” does not refer to computer programs only, But includes:
Computer Programs.
Associated documentation such as requirements, design models and user manuals.
Configuration data that is needed to make these programs operate correctly.
 Software Engineers: are concerned with developing software products.

8. What is Software 8
Software: computer programs, associated documentation and configuration data.
Good software should deliver the required functionality
and performance to the user and should be
maintainable, dependable and usable.
Programs
Software
System
Documentation
User
Data
Documentation

9. Software Engineering 9
 Software Crisis
The term "software engineering" first appeared in the1968 NATO Software Engineering Conference, and was meant to provoke thought regarding what was then
called the “software crisis”.
 Software Engineering (SWE)
Discipline of engineering 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.

10. Software Products Types10
 Generic products  Stand-alone systems that are marketed and sold to any customer who wishes to buy them.
Examples: PC software such as graphics programs, Excel or Word, CAD software and project management tools.
 Customized products (Bespoke)  Software that is commissioned by a specific customer to meet their own needs.
Examples: embedded control systems, air traffic control software, traffic monitoring systems and systems that support business process.
 Sometimes, these two types are overlapped  You can
buy standalone software and then you could do some
customization to it such as ERP system (SAP).

11. Software Process Activities11
 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.

12. Importance of Software Engineering12
 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 systems, the majority of costs are the costs of changing the software after it has gone into use.

13. Software Cost  Software costs often dominate computer system costs.13
 Software costs often dominate computer system costs.
 Software on a PC  the hardware cost.
 Software maintenance cost  the cost of developing it.
For systems with a long life, maintenance costs may be several times of development costs. Ex. Aircraft software.
 Software engineering is concerned with cost- effective software development.

14. Cost of Software Engineering14
 Depends on :
 The process used, and
 The type of software being developed
 Each generic approach has a different profile of
cost distribution.
 Roughly 60% of costs are development costs, 40% are testing costs.
 For custom software, evolution costs often
exceed development costs.

15. Software Engineering & Computer Science15
Computer Science  Theory + Fundamentals that underlie computers and software systems.
SWE  practical of developing and delivering useful software.

16. Software Engineering & System Engineering16
 System Engineering:
 Interdisciplinary engineering field (computer,
software, and process engineering).
 Focuses on how complex engineering projects should
be designed and managed.
System Engineering Software Engineering
• All aspects of • Deals with the design,
computer-based development and
systems development: delivery of SW.
HW + SW + Process • Is part of System
• Older than SWE Engineering.

17.  A set of activities that aims to produce SW product.
What is a Software Process? 17
 A set of activities that aims to produce SW product.
SW Process Activity What is going on there?
Specification What does the customer need?
Development Design & programming
Validation Checking whether it meets requirements
Evolution Modifications (e.g. customer/market)
What are the constraints?

18. Software Process Models Example18
 Waterfall approach
Requirements
definitions
System and
software design
Implementation
and unit testing
Integration and
system testing
Operation and
maintenance

19. Component-Based Software Engineering19
 Component-Based Software Engineering (CBSE):
 This technique assumes that parts of the system already exist.
 The system development process focuses on integrating these parts rather than developing them from scratch.

20. Essential Attributes of Good Software20
 Maintainability  Software should be written in such a way so that it can evolve to meet the
changing needs of customers.
 Dependability  Dependable software should not cause damage in the event of system failure.
 Efficiency  System resources: memory waste, processing time.
 Acceptability  This means that it must be
understandable, usable and compatible with other
systems that they use.

21. Key Challenges Facing Software Engineering21
 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.

22. Application Types  Stand-alone applications22
 Stand-alone applications
 These are application systems that run on a local computer,
such as a PC. They include all necessary functionality and do
not need to be connected to a network.
 Interactive transaction-based applications
 Applications that execute on a remote computer and are
accessed by users from their own PCs or terminals. These
include web applications such as e-commerce applications.
 Embedded control systems
 These are software control systems that control and manage
hardware devices. Numerically, there are probably more
embedded systems than any other type of system. 19

23. Application Types  Batch processing systems23
 Batch processing systems
 They process large numbers of individual inputs to create
corresponding outputs such as payroll system and invoice
system.
 Systems for modeling and simulation
 These are systems that are developed by scientists and
engineers to model physical processes or situations, which
include many, separate, interacting objects.
 Data collection systems
 These are systems that collect data from their environment
using a set of sensors and send that data to other systems for
processing. 20

24. Software Engineering Diversity24
 There are many different types of software systems and there is no universal set of software techniques that is applicable to all of these.
 The software engineering methods and tools used
depend on the type of application being developed, the requirements of the customer and the background of the development team.

25. Software Engineering Ethics25
 Software engineering involves wider responsibilities
than simply the application of technical skills.
 Software engineers must behave in an honest and
ethically responsible way if they are to be respected
as professionals.
 Ethical behaviour is more than simply upholding the law but involves following a set of principles that are morally correct.

26. Ethical principles Introduction Software Engineering
PUBLIC - Software engineers shall act consistently with the public interest.
CLIENT AND EMPLOYER - Software engineers shall act in a manner that is in the best interests of their client and employer consistent with the public interest.
PRODUCT - Software engineers shall ensure that their products and related modifications meet the highest professional standards possible.
JUDGMENT - Software engineers shall maintain integrity and independence in their professional judgment.
MANAGEMENT - Software engineering managers and leaders shall subscribe to and promote an ethical approach to the management of software development and maintenance.
PROFESSION - Software engineers shall advance the integrity and reputation of the profession consistent with the public interest.
COLLEAGUES - Software engineers shall be fair to and supportive of their colleagues.
SELF - Software engineers shall participate in lifelong learning regarding the practice of their profession and shall promote an ethical approach to the practice of the profession.
Software Engineering
Introduction

27. Ethical Dilemmas systems or nuclear systems.26
 Disagreement in principle with the policies of senior management.
 Your employer acts in an unethical way and releases a safety-critical system without finishing the testing of the system.
 Participation in the development of military weapons
systems or nuclear systems.

28. Software engineering and the web
The Web is now a platform for running application and organizations are increasingly developing web-based systems rather than local systems.
Web services allow application functionality to be accessed over the web.
Cloud computing is an approach to the provision of computer services where applications run remotely on the ‘cloud’.
Users do not buy software buy pay according to use.

29. Web software engineering
Software reuse is the dominant approach for constructing web-based systems.
When building these systems, you think about how you can assemble them from pre-existing software components and systems.
Web-based systems should be developed and delivered incrementally.
It is now generally recognized that it is impractical to specify all the requirements for such systems in advance.
User interfaces are constrained by the capabilities of web browsers.
Technologies such as AJAX allow rich interfaces to be created within a web browser but are still difficult to use. Web forms with local scripting are more commonly used.
Chapter 1 Introduction

30. Web-based software engineering
Web-based systems are complex distributed systems but the fundamental principles of software engineering discussed previously are as applicable to them as they are to any other types of system.
apply to web-based software in the same way that they apply to other types of software system.

31. Deliverables and Milestones
Some Terminologies
Deliverables and Milestones
Product and Process
Measures, Metrics, and Indicators
Chapter 1 Introduction

32. Cost, Schedule, and Quality
In the industrial-strength software domain, there are three basic forces at play—cost, schedule, and quality
The software should be produced at reasonable cost, in a reasonable time, and should be of good quality
Industrial-strength software is very expensive
The productivity in the software industry for writing fresh code generally ranges from few hundred to about LOC per person-month
Chapter 1 Introduction

33. Cost, Schedule, and Quality
Software companies often charge the client for whom they are developing the software between $ $15,000 per person-month
With a productivity of 1000 LOC(Line of code) per person-month, it means that each line of delivered code costs between $3 and $15! And even small projects can easily end up with software of 50,000 LOC. With this productivity, such a software project will cost between $150,000 and $750,000!
Chapter 1 Introduction

34. Cost, Schedule, and Quality
Schedule is another important factor in many projects
Business trends are dictating that the time to market of a product should be reduced; that is, the cycle time from concept to delivery should be small
Developing high-quality software is another fundamental goal of software engineering
Chapter 1 Introduction

35. Cost, Schedule, and Quality
The international standard on software product quality suggests that software quality comprises six main attributes
However, while cost is generally well understood, the concept of quality in the context of software needs further elaboration
Chapter 1 Introduction

36. Software quality attributes
Chapter 1 Introduction

37. Software quality attributes
Functionality: The capability to provide functions which meet stated and implied needs when the software is used
Reliability: The capability to provide failure-free service
Usability: The capability to be understood, learned, and used
Efficiency: The capability to provide appropriate performance relative to the amount of resources used
Chapter 1 Introduction

38. Software quality attributes
Maintainability: The capability to be modified for purposes of making corrections, improvements, or adaptation
Portability: The capability to be adapted for different specified environments without applying actions other than those provided for this purpose in the product
Chapter 1 Introduction

39. How do software engineers spend their time on the job ?
Software engineers probably spend less than 10% of their time writing code
The other 90% of their time is involved with other activities that are more important than writing code
Chapter 1 Introduction

40. How do software engineers spend their time on the job ?
Eliciting requirements
Analyzing requirements
Writing software requirements documents
Building and analyzing prototypes
Developing software designs
Writing software design documents
Researching software engineering techniques or obtaining information about the application domain
Chapter 1 Introduction

41. How do software engineers spend their time on the job ?
Developing test strategies and test cases
Testing the software and recording the results
Isolating problems and solving them
Learning to use or installing and configuring new software and hardware tools
Writing documentation such as users manuals
Attending meetings with colleagues, customers, and supervisors
Archiving software or readying it for distribution
Chapter 1 Introduction

42. Computer-Aided Software Engineering (CASE)
Tools support individual process tasks such as checking the consistency of a design, compiling a program and comparing test results
Tools may be stand-alone tools (e.g., a word processor) or grouped into workbenches
Chapter 1 Introduction

43. Classification of CASE Tools47
 CASE tools can be classified into:
 Upper-CASE:
Tools to support the early process activities of requirements and design.
 Lower-CASE:
Tools to support later activities such as programming, debugging and testing.

44. Computer-Aided Software Engineering (CASE)
Workbenches support process phases such as specification, design, etc. They normally consist of a set of tools with some greater or lesser degree of integration
Environments support all or at least a substantial part of the software process. They normally include several integrated workbenches

45. Tools, workbenches, environments
Software Engineering Software Processes

46. Exercises
A software organization plans to develop a system consisting of 36 KLOC. With a productivity of 900 LOC per person-month, find the required number of persons (developers) to develop this software in 40 days
A software organization plans to develop a system consisting of 45 KLOC. With a productivity of 900 LOC per person-month, find the number of days to develop this system if the number of developers is 30
Chapter 1 Introduction

47. Case Studies  A mental health case patient management system27
 A personal insulin pump
An embedded system in an insulin pump used by diabetics to maintain blood glucose control.
 A mental health case patient management system
A system used to maintain records of people receiving care for mental health problems.
 A wilderness weather station
A data collection system that collects data about weather conditions in remote areas.

48. Insulin pump control system
Collects data from a blood sugar sensor and calculates the amount of insulin required to be injected.
Calculation based on the rate of change of blood sugar levels.
Sends signals to a micro-pump to deliver the correct dose of insulin.
Safety-critical system as low blood sugars can lead to brain malfunctioning, coma and death; high-blood sugar levels have long-term consequences such as eye and kidney damage.
Dr.Doaa Sami

49. Insulin pump hardware architecture
Dr.Doaa Sami

50. Activity model of the insulin pump
Dr.Doaa Sami

51. Essential high-level requirements
The system shall be available to deliver insulin when required.
The system shall perform reliably and deliver the correct amount of insulin to counteract the current level of blood sugar.
The system must therefore be designed and implemented to ensure that the system always meets these requirements.
Dr.Doaa Sami

52. A patient information system for mental health care
A patient information system to support mental health care is a medical information system that maintains information about patients suffering from mental health problems and the treatments that they have received.
Most mental health patients do not require dedicated hospital treatment but need to attend specialist clinics regularly where they can meet a doctor who has detailed knowledge of their problems.
To make it easier for patients to attend, these clinics are not just run in hospitals. They may also be held in local medical practices or community centres.
Dr.Doaa Sami

53. MHC-PMS
The MHC-PMS (Mental Health Care-Patient Management System) is an information system that is intended for use in clinics.
It makes use of a centralized database of patient information but has also been designed to run on a PC, so that it may be accessed and used from sites that do not have secure network connectivity.
When the local systems have secure network access, they use patient information in the database but they can download and use local copies of patient records when they are disconnected.
Dr.Doaa Sami

54. MHC-PMS goals
To generate management information that allows health service managers to assess performance against local and government targets.
To provide medical staff with timely information to support the treatment of patients.
Dr.Doaa Sami

55. The organization of the MHC-PMS
Dr.Doaa Sami

56. MHC-PMS key features Individual care management Patient monitoring
Clinicians can create records for patients, edit the information in the system, view patient history, etc. The system supports data summaries so that doctors can quickly learn about the key problems and treatments that have been prescribed.
Patient monitoring
The system monitors the records of patients that are involved in treatment and issues warnings if possible problems are detected.
Administrative reporting
The system generates monthly management reports showing the number of patients treated at each clinic, the number of patients who have entered and left the care system, number of patients sectioned, the drugs prescribed and their costs, etc.
Dr.Doaa Sami

57. MHC-PMS concerns Privacy Safety
It is essential that patient information is confidential and is never disclosed to anyone apart from authorised medical staff and the patient themselves.
Safety
Some mental illnesses cause patients to become suicidal or a danger to other people. Wherever possible, the system should warn medical staff about potentially suicidal or dangerous patients.
The system must be available when needed otherwise safety may be compromised and it may be impossible to prescribe the correct medication to patients.
Dr.Doaa Sami

58. Wilderness Weather Station28
 The government of a country with large areas of wilderness decides to deploy several hundred weather stations in remote areas.
 Weather stations collect data from a set of instruments that measure temperature and pressure, sunshine, rainfall, wind speed and wind direction.
The weather station includes a number of instruments that measure weather parameters such as the wind speed and direction, the ground and air temperatures, the barometric pressure and the rainfall over a 24-hour period. Each of these instruments is controlled by a software system that takes parameter readings periodically and manages the data collected from the instruments.

59. The Weather Station’s Environment29
Weather station system: collecting weather data and transmitting them to the data management system.
Data management and archiving system: collects data from all of wilderness weather stations, carries out data processing and archives the data.
Station maintenance system: communicate by satellite with all wilderness weather stations to monitor the health of these systems and provide reports of problems.

60. Summary maintainability, dependability and security, efficiency30
Software engineering is an engineering discipline that is concerned with all aspects of software production.
 Essential software product attributes are
maintainability, dependability and security, efficiency
and acceptability.
The high-level activities of specification, development,
validation and evolution are part of all software
processes.
 Software engineers have responsibilities to the
engineering profession and society. They should not
simply be concerned with technical issues.

61. Thank you End of Chapter 1