BEST PRACTICES

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BEST PRACTICES

• Developing Software Solutions

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Introduction

• Chapter 1
• Best Practices

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Principles and Best Practices

• Strive to design and build successful
  high-quality solutions
• Various techniques or methods have proven to lead
  to success best practices
• Useful in field of software development and
  others
• Basic general rules principles
• Guides behaviour of software developers
• Guidelines principles best practices
• Software developer should be aware and apply

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The Beginning

• Concept computer program
• Application
• Programming constructs and concepts
• Programming is a craft

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The Architecture of an Application

• Software development not simply writing small
  programs
• Payroll application
• Computes employee salaries
• Determines taxes payable
• Prints payslips
• Requires set of organised data database
• User interface - that part of the program with
  which user interacts
• Menu system set of forms
• Set of Web pages accessible via Web browser

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The Architecture of an Application

• Various elements working together called system
• Different businesses
• Different business
• Different needs
• Application vary in structural design
  (architecture)

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Single-user database application

• Application, its user interface and database
  exist on single computer
• Database engine lies between the application and
  the database
• Adv of placing database engine between
  application and database
• Offers programmer independence from particular
  database being accessed
• Same programming techniques used to access
  database regardless of database type
• Application updates?

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Single-user database application
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Multi-user database application

• Data placed on central computer to be accessed
  remotely over a network by other computers
• Only 1 DBMS required (1 database server)
• Disadvantages
• More concurrent users, heavier load reduce
  performance of database server (processing power
  shared)
• Security restrict access of unauthorized users
  (log on authenticating)
• Application updates?

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Multi-user database application
Users Computer
Users Computer
Order Processing Application
Order Processing Application
Network
Database Server
Order Database
Database Engine
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Internet database application

• Web interface (A) - Web browser provides basic
  interface via Internet
• Rich interface (B) for more complex tasks (main
  user interface portion created using i.e. VB.Net)
• Main core of application placed on application
  server
• Application invokes services of database server
• Deployment admin tasks simpler most
  application logic on centralized server

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Internet database application
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Internet database application

• Disadvantages
• Too many users poor performance
• Security threat of exposure to unauthorized
  users inside outside company (firewall)

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Important Issues for Consideration

• Your program is often a small component of a much
  Bigger Picture
• Ensure that interface of each created element is
  easy to use (simplicity of code for components
  function, classes etc.)
• Anticipate how application will evolve in future
  design accordingly (single user vs multiple
  user application?)
• Build application with flexibility in mind

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Important Issues for Consideration

• Protection of data or parts of application from
  unauthorized access.
• Build applications to simplify deployment,
  administration and maintenance.

Always keep thinking ahead.
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Object-Oriented Programming

• Allows for the creation, use and maintenance of
  reusable software by splitting a program up into
  units that combine data and instructions
• (packaging related data and behavior together
  encapsulation).
• Units called objects

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An Object

• Possesses a state that is encapsulated within
  the object.
• Exhibits behavior in that it respond to external
  events.
• Possesses an identity in that there may be more
  than one object of a given type.

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Objects can represent

• Physical things (customers and products)
• Conceptual things (orders and loans)
• Organizational things (companies and departments)
• Objects in the real world translate into
  objects in the software system.
• Other examples of objects windows and
  buttons

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An object has

• Attributes data items that define it
• (Product object with product ID attribute)
• Methods defines an associated action and is
  used to inspect or modify an objects state (also
  called operations)
• Messages used for interaction and collaboration
  between objects.

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Classes

• Formal definitions that provide basis for all
  objects
• Blueprint or template for the creation of an
  object
• Defines all the behaviors and attributes of the
  class.

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Example of a class

• Class can define everything about a real-world
  object such as a motor vehicle
• The defined attributes wheels, engine, doors
  and others
• The defined methods stop and go

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Object continued

• Also called instance
• Is the implementation of the class at run-time
• Each object has an interface the set of
  publicly exposed methods and properties used to
  manipulate the object.
• Interface provides a means of executing internal
  code without exposing implementation detail to
  user of the object

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Object continued

• Inner workings of object hidden from the user,
  but interface exposed to outside.
• Data abstraction unnecessary level of detail is
  hidden.
• Only need information about public interface to
  use object
• Internal representation of objects data and
  operations is irrelevant and invisible to the
  user of an object.

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Class representation
Class name
Class attributes
Class operations
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Instance of Class
TRUCK
registration CWZ251 Speed 60 Fuel 2.2
litres Temperature cool
Object holds actual values
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Objects

• Work with objects in Visual Basic .NET, C, JAVA
• Controls,
• Forms
• Data access objects
• Create own objects, by defining additional
• Properties and
• Methods
• Objects prefabricated building blocks
• Write a piece of code once and
• Reuse it again and again

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Object Oriented System Characteristics

• System will have
• Relatively little global data
• A structure comprising of a network of objects
• Objects will be
• Self-sufficient - Independent -Clearly defined
  interfaces
• Data will
• only be able to be manipulated using publicly
  defined methods.
• Be hidden inside the object
• Inaccessible to parts of the system that do not
  need to see it.
• These features promotes ease of carefully testing
  each object in isolation

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Component

• Compiled piece of code that is based on the
  aggregation of many classes a compiled entity
• create a set of classes that define the data
  access logic for the application.
• Compile classes into single component
• Create an instance of the class (defined within
  the component) by first installing the component
  containing the class
• Example electronics switches, instruments and
  starter motors
• Once built
• Reused

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Object Oriented Concepts
Object Software unit packaging together data and methods to manipulate that data
Class Template for creating objects
Attribute Data item defined as part of a class or object
Operation Procedure or function defined a part of a class or object using this term refers to the procedures public interface with the rest of the software.
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Object Oriented Concepts
Method Procedure of function defined as part of a class or object using this term refers to the procedures implementation
Message Request sent to an object to execute one of its methods.
Encapsulation Packaging data and operations into an object
Data hiding Making the internal details of an object inaccessible to other objects.
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Object Oriented Concepts
Inheritance Mechanism that allows a new class to be defined as a specialization of another. The specialized class automatically inherits the features of the class it is created from, and can add additional features or change or suppress inherited features.
Polymorphism Mechanism that allows a single message to be interpreted differently by different object. The ability to hide different implementations behind a common interface.
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The Applications role in the IS
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The Applications role in the IS

• Always ensure that any application integrates
  with the IS and supports its goals fully.
• Goal of an IS for all its components to
• Collect
• Transform
• Store
• Provide accurate, timely and useful information

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A Process Must be Followed

• Application design depends on specific
  requirements
• problems to be solved
• process to be automated
• people (users)
• Framework needed for developing maintaining
  software
• successive phases followed in orderly way.
• SOFTWARE DEVELOPMENT LIFE CYCLE (SDLC)

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SDLC

• Feasibility study
• Requirements elicitation
• Analysis
• Architectural design
• Detailed design
• Coding (implementation)
• Unit and integration testing
• Operation and maintenance

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The effective / productive programmer

• Early adopter / fast adapter
• Inquisitive
• Critical Thinker
• Realistic
• Jack of all trades

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Exercising your curiosity

• Build your awareness of the development process
• Experiment
• Read about problem solving
• Analyse and plan before you act
• Learn about successful projects
• Read!
• Read other books and periodicals
• Affiliate with other professionals
• Make a commitment to professional development

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Attitude

• Be willing to work hard
• Care about what you do
• Aim to get things right the first time
• Concern yourself with aesthetics
• Think about your work
• Be disciplined
• Develop good habits

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Attitude

• Be aware of the bigger picture
• Take responsibility for everything you do.
• Dont tolerate or ignore software rot
• Welcome change, and also be aware of it
• Listen to the ideas of other people
• Produce quality software

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Attitude

• Be intellectually honest
• Refuse to pretend you are an expert when you are
  not
• Readily admitting your mistakes
• Try to understand a compiler warning rather than
  suppressing the message.
• Clearly understand your program not compiling
  it to see if it works.
• Provide realistic status reports
• Provide realistic schedule estimates and holding
  your ground when management asks you to adjust
  them.

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Attitude

• Listen to your inner voice
• Improve your communication skills
• Know what you want to say
• Know your audience
• Choose your moment
• Choose a style
• Make it look good
• Involve your audience
• Be a listener
• Get back to people

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Strive to be a superior developer

• The characteristics of a superior developer
• have very little to do with talent
• and everything to do with devotion to
• personal development

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Solving Problems

• Some constraints are simply our own preconceived
  ones.
• Is there an easier way?
• Are you trying to solve the right problem?
• Why is this thing a problem?
• What is it that is making it so hard to solve?
• Does it have to be done this way?
• Does it have to be done at all?

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Building Quality Systems

• Defect rate one chip in 10 000
• strive towards truly perfect solutions
• devote to quality throughout design development
  design quality into your application
• Fitness for purpose ultimate measure of quality
  meet the basic requirement first

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Quality systems

• Factors of interest to client
• System needs to be
• Delivered on time
• Reasonably priced
• User-friendly
• Reliable
• Factors of interest to developer
• Good program design
• Efficient use of resources
• Well-structured database
• maintainability

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Measuring software quality

• Correctness
• Accuracy
• Usability
• Efficiency
• Performance
• Availability
• Reliability
• Robustness
• Scalability
• Adaptability
• Securability

Completeness
Consistency
Robustness
Budgen (2003)
McConnel (2004)
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Additional quality factors

• Maintainability
• Manageability
• Flexibility
• Portability
• Reusability
• Testability
• Readability
• Understandability

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Quality

• Maximizing one quality characteristic might
  compromise another
• Find an optimal solution from a set of competing
  quality objectives.
• Get it right the first time
• quality assurance
• Fact Improving quality
• Reduces development costs
• Shortens development time
• Increases productivity

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Primary goal of software development

• To deliver high-quality, maintainable software
  projects on time and within budget
• Secondary goals
• Meeting and satisfying the intended users
  requirements
• Containing development costs
• Avoiding the failure of the software development
  project

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Statistics Software projects failure

• 80 fail due to
• Over budget
• Late
• Missing functionality
• Combination of all three above
• 30 poorly executed
• Thus project cancelled before completion

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Conclusion