Software Engineering Introduction

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Software Engineering Introduction

• DESIGN ENGINEERING
• Software design is an iterative process through
  which requirements are translated into a
  blueprint for constructing software.
• A design must implement all of the explicit
  requirements contained in the analysis model, and
  it must accommodate all of the implicit
  requirements desired by the customer.
• A design must be a readable, understandable guide
  for those who generate code and those who test
  and subsequently support the software.
• The design should provide a complete picture of
  the software, addressing, the data, functional,
  and behavioral domains from an implementation
  perspective.

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Software Engineering Introduction

• DESIGN ENGINEERING
• FURPS Functionality, Usability, Reliability,
  Performance, and Supportability.

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Software Engineering Introduction

• DESIGN ENGINEERING
• FURPS Functionality, Usability, Reliability,
  performance, and supportability.
• Functionality assessed by evaluating
• the feature set
• capabilities of the program.

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Software Engineering Introduction

• DESIGN ENGINEERING
• FURPS Functionality, Usability, Reliability,
  Performance, and Supportability.
• Usability - assessed by considering
• human factors,
• overall aesthetics,
• consistency,
• end-user documentation.

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Software Engineering Introduction

• DESIGN ENGINEERING
• FURPS Functionality, Usability, Reliability,
  Performance, and Supportability.
• Reliability is evaluated by measuring
• the frequency and severity of failure,
• the accuracy, of output results,
• the mean-time-to-failure,
• the ability to recover from failure,
• the predictability of the program.

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Software Engineering Introduction

• DESIGN ENGINEERING
• FURPS Functionality, Usability, Reliability,
  Performance, and Supportability.
• Performance is measured by
• processing speed,
• response time,
• resource consumption,
• throughput,
• efficiency

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Software Engineering Introduction

• DESIGN ENGINEERING
• FURPS Functionality, Usability, Reliability,
  Performance, and Supportability.
• Supportability combines
• the ability to extend the program
  (extensibility),
• adaptability,
• serviceability
• testability,
• compatibility,
• configurability.

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Software Engineering Introduction

• DESIGN ENGINEERING
• Abstraction is one of the fundamental ways that
  we as humans cope with complexity. Grady Booch
• What kinds of things do we abstract?

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Software Engineering Introduction

• DESIGN ENGINEERING
• Abstraction is one of the fundamental ways that
  we as humans cope with complexity. Grady Booch
• What kinds of things do we abstract?
• data
• objects
• procedures
• modules
• just about anything

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Software Engineering Introduction

• DESIGN ENGINEERING
• Abstraction is one of the fundamental ways that
  we as humans cope with complexity. Grady Booch
• What kinds of things do we abstract?
• data
• objects
• procedures
• modules
• just about anything

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Software Engineering Introduction

• DESIGN ENGINEERING
• ARCHITECTURE
• Software architecture alludes to the overall
  structure of the software and the ways in which
  that structure provides conceptual integrity for
  a system.
• Architecture is
• the structure or organization of program
  components (modules),
• the manner in which these components interact,
• the structure of data that are used by the
  components.

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Software Engineering Introduction

• DESIGN ENGINEERING
• PATTERNS
• A pattern is a named nugget of insight which
  conveys the essence of a proven solution to a
  recurring problem within a certain context amidst
  competing concerns.
• Each pattern describes a problem which occurs
  over and over again in our environment, and then
  describes the core of the solution to that
  problem, in such a way that you can use this
  solution a million times over, without ever doing
  it the same way twice. Christopher Alexander

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Software Engineering Introduction

• DESIGN ENGINEERING
• MODULARITY
• Software is divided into separately named and
  addressable components, sometimes called modules,
  that are integrated to satisfy problem
  requirements.

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Software Engineering Introduction

• DESIGN ENGINEERING
• INFORMATION HIDING
• Modules should be specified and designed so that
  information (algorithms and data) contained
  within a module is inaccessible to other modules
  that have no need for such information.
• This means that inadvertent errors introduced
  during modification are less likely to propagate
  to other locations within the software.
• Changes to the internal representation of one
  module should have not have an effect on other
  modules.

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Software Engineering Introduction

• DESIGN ENGINEERING
• FUNCTIONAL INDEPENDENCE
• Functional independence is achieved by developing
  modules with single-minded function and an
  aversion to excessive interaction with other
  modules.
• We want to design software so that each module
  addresses a specific subfunction of requirements
  and has a simple interface when viewed from other
  parts of the program structure.
• Independence is assessed by using two qualitative
  criteria
• Cohesion How related a module is to itself. It
  should perform a single task and require little
  interaction with the rest of the program.
• Coupling is an indication of the interconnectoin
  among modules in a software structure.

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Software Engineering Introduction

• DESIGN ENGINEERING
• REFINEMENT
• Stepwise refinement is when a program is
  developed by successively refining levels of
  procedural detail.
• Refinement is actually the process of
  elaboration.
• REFACTORING
• Refactoring is a reorganizational technique that
  simplifies the design )of code) of a component
  without changing its function or behavior.