IB Computer Science HL

• Changing Software Systems (Considerations)

  • Extent of change
  • Limitations of new system
  • Context in which the system will be used
  • Organizational Issues
  • Change in User Roles
• Changing Software Systems (Challenges)

  • Users don't like change
  • Some features may be omitted
  • Old systems may be faster
  • Incompatibility with other systems
  • Data loss
  • Expensive
• Changing Software Systems (Methods)

  • Direct Changeover
  • Parallel
  • Pilot
  • Phased
• Direct Changeover


  • Old system stopped, then new started
  • Changeover swift, new system available immediately
• Parallel


  • Old and new system run concurrently - new data entered into both
  • Backup if new system fail, output from both system can be compared to verify that new system works correctly
• Pilot


  • New system tested with small part of organization, bugs fixed, then expanded
  • All features tested before adoption by whole organization, staff who are part of pilot can train others, if failure, only small part suffers
• Phased


  • Introduced in phases, old system gradually phased out
  • Allows people to get used to new system, training can be done in stages
• Data Migration (Problems)


  • Incompatible file formats
  • Data structure differences
  • Validations rules
  • Incomplete data transfers
  • Different data, currency, or character conventions
• Legacy Systems


  • Old technology, computer system or application
  • No longer supported/available for purchase
  • Modernization may be expensive or time-consuming
• Local Software


  • Runs on your computer
  • One-time fee
  • Installation
  • Update may not be automatic
  • Can be used on one computer
• Remote (SAAS) Software


  • Accessed through a web browser
  • Subscription fee
  • Can use used on any number of computers via web browser
  • Automatic Updates
  • Users always using the same version
• SAAS (Software-as-a-Service) Pros


  • Employees can operate software from anywhere
  • Cheaper
  • Fewer support staff necessary
  • Pay as you go/Subscription model
  • Scaling up to serve more users easy
  • Easier to maintain - don't need to worry about individual computer problems
• SAAS (Software-as-a-Service) Cons


  • Users have no control over availability of system
  • Users have no control over security
  • If SAAS provider gets acquired, user has no control over system
  • Large-scale data corruption possible
• Testing


  • Static Testing
  • Dynamic Testing
• Static Testing


  • Did we build the right system?
  • Examines documentation, planned specifications, test plans etc.
  • Verification of documentation
• Dynamic Testing


  • Code is executed
  • Makes sure code produced required result
  • Checks for bugs
  • Software meets business requirements
  • Validation - makes sure software operates as expected
• Testing Types


  • Alpha Testing
  • Beta Testing
  • Black Box Testing
  • White Box Testing
  • User Acceptance Testing
  • Automated Testing
• Alpha Testing


  • Testing done by internal team
  • Lasts for months
  • Very structures
  • Confirms software works as intended
  • Looks for bugs or UI issues to fix
• Beta Testing


  • Used by potential end-users outside of company
  • Lasts for weeks
  • Largely unstructured, seeks to model real-world environment
  • Seeks to get feedback from users
  • Uses feedback to fix bigs and make software more useful for end-users
• Black Box Testing


  • Tests software through using it
  • No access to codebase or internal workings
  • No programming knowledge required
• White Box Testing


  • Tests a software program's code to make sure everything is working
  • Programming knowledge required; done by programmers
• User Acceptance Testing


  • End-user testing
  • Product is tested by intended audience
• Automated Testing


  Uses software to automatically test other software
• Dynamic Testing


  Code is executed to make sure it produced the required result, checks for bugs, and ensures software meets business requirements
• Validation


  Makes sure software operates as expected
• Alpha Testing


  • Testing done by internal team, lasts for months, very structured, confirms software works as intended, looks for bugs or UI issues to fix
• Beta Testing


  • Used by potential end-users outside of company, lasts for weeks, largely unstructured, seeks to model real-world environment, seeks to get feedback from users, uses feedback to fix bugs and make software more useful for end-users
• Black Box Testing


  Tests software through using it, no access to codebase or internal workings, no programming knowledge required
• White Box Testing


  Tests a software program's code to make sure everything is working, programming knowledge required, done by programmers
• User Acceptance Testing


  End-user testing, product is tested by intended audience
• Automated Testing


  • Uses automated testing software, tests preconstructed (usually specified in software or written in code), program output automatically compared to expected output, can rapidly complete complex/tedious tasks
• User Documentation Types


  • Manual (Paper manual, booklet, or pamphlet)
  • Online (PDFs, website, video)
  • Help files (Locally accessible programs that display text)
• User Training Methods


  • In-person classes
  • Online training - Instructor training one student or small group of students
  • Self-instruction
• Causes of Data Loss

  • Hardware/System Malfunction
  • Human Error
  • Software Corruption
  • Malicious Software (Viruses, etc.)
  • National Disasters (Power cuts = equipment damage)
• Ways of Preventing Data Loss

  • Failover Systems
  • Redundancy
  • Removable Media
  • Offsite/online storage
  • Physical Security
• Stakeholders


  A person with an interest or concern in something (especially a business)
• Stakeholder Methods to Get Requirements for Software Functionality

  • Direct Observation
  • Interviews
  • Surveys
  • Prototypes
• Iteration


  Cyclical process that ends in a finished product, process of prototyping, testing, analyzing test results, and refining product until requirements met, allows constant improvement based on user or client feedback
• Software Deployment


  • Release
  • Update
  • Bug
  • Security Vulnerability
  • Patch
  • Upgrade capability
  • Upgrade Driver
• Usability


  How effectively and efficiently a product can be used