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Chapter 1 Introduction to Software Engineering. Why Engineer Software?. Air traffic control case study $2.3 Billion spent without any usable deliverable Enormous social cost of NOT engineering software Too many large-scale software development failures for too many decades

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why engineer software
Why Engineer Software?
  • Air traffic control case study
    • $2.3 Billion spent without any usable deliverable
  • Enormous social cost of NOT engineering software
  • Too many large-scale software development failures for too many decades
  • Software development initiatives fail for many different reasons, most of which are addressed by good software engineering practices
sources of complexity in software development
Sources of Complexity in Software Development
  • Technical staff lacks expertise in the complex application domain
  • Difficulty in interpersonal communications
  • Ambiguity of natural language, used to express user needs
  • Difficulty of mentally grasping and coordinating the details of a large-scale development project
how software development projects fail
How Software Development Projects Fail
  • No functioning software results
  • The resulting software does not adequately address the need of the users
  • Software contains incorrect computations
  • The software is too difficult to use correctly
  • The system response time is too slow to be used without frustration
why inter personal communication is difficult
Why Inter-personal Communication is Difficult
  • Technical staff and end users have different background knowledge
  • Technical staff often do not possess the vocabulary used in the application domain
  • End users frequently do not understand how to effectively express their needs in terms that are clear to systems developers.
  • Ambiguity of natural language
maintaining software systems
Maintaining Software Systems
  • Maintenance is an inevitable aspect of software development
  • It allows software to evolve with an organization
  • Too often too many resources are directed to maintenance and away from new development
  • Software requires excessive maintenance efforts if it is poorly structured
  • It is better to invest in well-structured software up front than to invest excessively in maintenance later
elements of a software development paradigm
Elements of a Software Development Paradigm
  • Conceptualization
    • What elements are instrumental in how the developers think about the software system?
  • Representation
    • Must convey what the software project is all about
    • Most effectively done with a software modeling notation
  • Implementation
    • Addresses how the source code is structured
a brief history of software engineering techniques
A Brief History of Software Engineering Techniques
  • Structured Programming
    • No gotos
  • Functional Decomposition
    • Top-down organization of subprograms
  • Structured Analysis
    • Recognition that analyzing the problem statement has critical influence on the success of the overall project
    • Formal modeling of subprogram interaction with dataflow diagrams
more history of se techniques
More History of SE Techniques
  • Data-centered analysis
    • Uses techniques developed in structured analysis
    • Data modeling occurs using entity relationship diagrams before functional modeling
  • Object-oriented analysis
    • No longer segregates the modeling of functions and data
    • Objects aggregate data with functions that operate on the data
sample dataflow diagram
Sample Dataflow Diagram

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sample entity relationship diagram
Sample Entity Relationship Diagram




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principles of the object oriented paradigm
Principles of the Object-Oriented Paradigm
  • Abstraction
  • Modularity
  • Modeling
  • Inheritance
  • Encapsulation(covered in chapter2)
  • Polymorphism(covered in Chapter2)

Shared by other paradigms

  • Expressing the software requirements in abstract terms, suppressing details so that a comprehensive portrayal can be made
  • The abstract representation must then be connected to more detailed expressions, so that no information is lost in modeling the system
  • This allows us to reason about the breadth of functionality of the developing system
  • Breaking a complex software system into smaller modules allows one to reduce its overall complexity
  • Modules should aggregate some coherent aspect of the system
  • Modules should present a simple interface
  • Classes, functions, and abstract data types are examples of modules.
abstract data type example
Abstract Data Type Example









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Implementation Option: Array

Implementation Option: Linked list

  • Modeling is the process of use a graphic notation to express properties of the software system
  • Models express how the system is built out of modules and how these modules interact
  • One objective of modeling is to express characteristics of the software system in an unambiguous manner
  • A property distinguishing classes from abstract data types
  • Allows characteristics from one class to be passed on its subclasses
  • Subclasses may override inherited characteristics
cost of not engineering software
Cost of not Engineering Software
  • Need to restructure code
  • High maintenance costs
  • Software is unacceptable to end users
  • Unreliable code
  • Need to rewrite code
  • Difficulty integrating system modules
  • Difficult project management
  • Budget and time overruns
why software engineering is not universal
Why Software Engineering is not Universal
  • Understanding software development as programming only without recognition of importance of analysis and design
  • Short-sighted technical management
  • Pressure of deadlines
  • Poor project estimation, thus unreasonable deadlines
working in teams
Working in Teams
  • Be conscientious about due dates
  • If you are less motivated by the class project, negotiate an equitable grade and take a lesser role
  • Meet regularly with your team
  • Always create an agenda for every team meeting
  • Rotate responsibility for chairing team meetings