SOFT3010: ObjectOriented Development

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SOFT3010 Object-Oriented Development

• Alan OCallaghan
• Object Engineering Migration group
• aoc_at_dmu.ac.uk

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Trends in Software Engineering

• Two sweeping trends dominate the (short) history
  of Software Engineering
• the shift in focus from programming-in-the-small
  to programming-in-the-large
• the evolution of higher order programming
  languages
• These changes in turn impact on software
  architecture, the development process, and
  development team organisation

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The Generations of Programming Languages (1)

• First Generation (1954-1958)
• FORTRAN I Mathematical expressions
• ALGOL 58 Mathematical expressions
• Flowmatic Mathematical expressions
• IPL V Mathematical expressions
• Second Generation (1959-1961)
• FORTRAN II Subroutines, separate compilation
• ALGOL 60 Block structures, data types
• COBOL Data description, file handling
• Lisp List processing, pointers, etc.

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The generation of Programming Languages (2)

• Third Generation (1962-1970)
• PL1 FORTRANALGOLCOBOL
• ALGOL 68 ALGOL 60 rigour
• Pascal Simple successor to ALGOL 60
• Simula 67 Classes, data abstraction
• The Generation Gap (1970-80)
• Many new languages, only C endured
• Fourth Generation
• Progress Application Generator

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The genesis of OO

• Simula 67 was the first OO language
• but was considered structured
• Smalltalk 80 is the mother of modern OO languages
  and concepts
• Byte articles in 1981 introduced OO to
  programmers
• Eiffel, C, Objective-C , CLOS and Object
  Pascal followed in the mid-eighties Java in 1996

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The Topology of First and Early Second Generation
Languages
Data
Subprograms
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The Topology of Second and Early Third Generation
Languages
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The Topology of Late Second and Early Third
Generation Languages
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The Topology of Object-oriented Languages
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Elements of the Object Model

• Booch identifies four major elements of the
  Object Model
• Abstraction
• Encapsulation
• Modularity
• Hierarchy
• And three minor elements
• Typing concurrency persistence

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Abstraction

• An abstraction denotes the essential
  characteristics of an object that distinguish it
  from other kinds of objects and thus provide
  crisply defined conceptual boundaries, relative
  to the perspective of the viewer

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Encapsulation

• Encapsulation is the process of
  compartmentalizing the elements of an abstraction
  that constitutes its structure and behaviour
  encapsulation serves to separate the contractual
  interface of an abstraction and its
  implementation

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Modularity

• Modularity is the property of a system that has
  been decomposed into a set of cohesive and
  loosely coupled modules

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Hierarchy

• Hierarchy is the ranking or ordering of
  abstractions

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Typing

• Typing is the enforcement of the class of an
  object, such that objects of different types may
  not be interchanged, or at most, that may be
  interchanged in very restricted ways

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Concurrency

• Concurrency is the property that distinguishes
  an active object from one that is not active

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Persistence

• Persistence is the property of an object through
  which its existence transcends time (i.e. the
  object continues to exist after its creator
  ceases to exist) and/or space (ie.the objects
  location moves from the address space in which it
  was created).

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Open Issues

• What exactly are classes or objects?
• How do you properly define the classes and
  objects that are relevant?
• What is a suitable notation for expressing the
  design of an OO system?
• What process can lead us to a well-structured OO
  system?
• What are the management implications of using
  objects?