Object-Oriented Development

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Object-Oriented Development

• By Linda M. Northrop
• vol. 1, chapter 5, pp. 291-300

Presented by Gleyner Garden EEL6883 Software
Engineering II
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Introduction

• The paper was written in 1994 and provides an
  overview of object-oriented methodologies
• Describes the history of object-oriented methods,
  models of object-oriented design, and concepts of
  object-oriented programming
• Most of you probably already knew most of this
  stuff as you were reading but when this paper
  was written, a lot of these ideas were new to a
  lot of people

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Historical Perspective

• Was initially thought of as a research
  curiosity
• Object-oriented programming is today what
  structured programming was in the 1970s
• The Object and object attribute idea first
  conceived in the 1950s for A.I.
• The real movement began in 1966 with the
  introduction of the Simula language

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Historical Perspective

• Palo Alto Research Center (PARC) developed
  Smalltalk in the early 1970s
• Smalltalk is considered the first truly
  object-oriented language
• Led other languages to support object-oriented
  programming
• examples Objective-C, C, Self, Eiffel, and
  Flavors
• 1980 Booch pioneered the concept of
  object-oriented design (OOD)

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Motivation

• Benefits are Greater
• Productivity
• Reliability
• Maintainability
• Manageability

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Motivation

• Direct mapping of concepts in the problem domain
  to software units and their interfaces
• Viewing the world as objects is more natural
  since it is closer to the way humans think
• Objects are more stable than functions
• Supports information hiding, data abstraction,
  and encapsulation

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Motivation

• Easily modified, extended, and maintained
• if your product was designed correctly

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Object-Oriented Model

• A new way of thinking about what it means to
  compute and how information can be structured
• Systems are viewed as cooperating objects that
  encapsulate structure and behavior in a
  hierarchical construction
• Functionality achieved by messages passing
  between objects

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Object-Oriented Model

• Object-oriented model can be viewed as the
  framework containing
• Abstraction
• Encapsulation
• Modularity
• Hierarchy
• Typing
• Concurrence
• Persistence
• Reusability
• Extensibility

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Object-Oriented Model

• The integration of procedural and data-driven
  approaches

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Object Oriented Programming

• Concepts
• Programs are organized into cooperating
  collections of objects
• Object entity that encapsulates state and
  behavior. An instance of a class
• Interface or protocol set of messages to which
  it will respond
• Response can be a message or routine, or
  delegation of the message to another object

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Object Oriented Programming
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Languages

• 4 Branches of object-oriented languages, with
  Simula being the common ancestor
• Smalltalk-based
• C-based
• Objective-C, C, Java
• LISP-based
• Flavors, XLISP, LOOPS, CLOS
• PASCAL-based
• Object Pascal, Turbo Pascal, Eiffel, Ada 95

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Languages

• Object-based languages
• Alphard
• CLU
• Euclid
• Gypsy
• Mesa
• Ada
• Want to learn more about these languages
  (history, where their names came from, etc)?
  click here

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Life Cycle

• If it is accepted that object-oriented is more
  than object-oriented coding, then a whole new
  approach, including life cycle, must be adopted
  (Booch, 1994)

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Life Cycle

• Waterfall consists of a sequential process,
  primarily in one direction
• Does not accommodate real iteration
• Criticized for placing no emphasis on reuse and
  having no unifying model to integrate the phases

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Life Cycle

• Water fountain life cycle describes the inherent
  iterative and incremental qualities of
  object-oriented development
• Prototyping and feedback loops are standard

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Object-Oriented Analysis

• Examines requirements from the perspective of the
  classes and objects found in the vocabulary of
  the problem domain
• Yields black-box objects that are derived from
  the problem domain
• Scenarios can be used to determine necessary
  object behavior

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Analysis example

• Problem Drawing shapes
• Scenarios
• Draw a point
• Draw a line
• Draw a circle
• Draw a square
• Draw a rectangle
• Draw a polygon

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Object-Oriented Design

• Object focus shifts to the solution domain
• Objects, their semantics, and relationships are
  identified
• Implementation and iteration occur
• Jacobsen says when details of the implementation
  begin to show, its OOD
• In my practice OOA is preliminary design, and
  OOD is detailed design

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Management Issues

• Object-oriented development requires a commitment
  to change processes, resources, and
  organizational structure.
• LOC measurements are less valuable, of classes
  reused, inheritance depth, number of
  class-to-class relationships, object coupling,
  total of classes, and class sizes are more
  valuable and meaningful

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Management Issues

• Booch suggests smaller development teams, and
  cultivation of reuse experts
• Reward reuse, not LOC build libraries and
  application frameworks
• QA review and testing activities still
  essential, but timing and definition are
  different
• Tools everything described exists in visual
  studio

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Object-Oriented Transition

• Levels of absorption before assimilation into a
  software development organization occurs
• Training is essential
• Pilot projects are recommended
• Combining structured and object-oriented
  approached not recommended

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Object-Oriented Transition

• Total object-oriented approach recommended for
  the following reasons
• Traceability improvement
• Reduction in significant integration problems
• Improved conceptual integrity of process and
  product
• Less need for objectification and
  deobjectification
• Maximization of the benefits of object-orientation

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The Future

• The future is now object-oriented development is
  pretty standard
• Class libraries and application frameworks
  (exist)
• Transparent information access across
  applications and environments (exists)
• Movement will gain popularity (did)

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Conclusion

• This paper was pretty cutting-edge when it was
  first published

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Questions? Comments?

• Feel free to speak up!