IB Computer Science SL: System fundamentals

Considerations when changing software systems

• Extent of change

• Limitations of new system

• Context in which the new system will be used

  • Organisational issues

  • Change in user roles

Challenges with changing software systems

• Users don’t like change

• Some previous features may be omitted

• Old systems may be faster

• New system incompatible with other systems

• Risk of data loss

• Expensive

Direct changeover (system changeover)

When the old system stops and the new system immediately starts running.

• Pros: Fast changeover, new system available immediately.

• Con: No backup in case of failure.

Parallel running (system changeover)

Old and new system run simultaneously.

• Pros: Backup if new system fails

• Cons: Running both systems at the same time is expensive

Pilot changeover (system changeover)

New system is tested with a small part of the organisation, bugs are fixed, and then the new system expands to the whole organisation.

• Pros: All features are tested, staff can train others, if it does fail - only a small part suffers

• Cons: No backup for pilot group

Phased changeover (system changeover)

New system is introduced in stages, gradually phasing out the old system.

• Pros: People can get used to the new system, training can be done in stages

• Cons: No backup if system fails for certain stage

Data migration

Moving data from one system to another. Depending on the size of the system, it can be a huge process. However, it is necessary when transitioning to new system.

Problems with data migration

• Incompatible file formats

• Data structure differences

• Validation rules

• Incomplete data transfers

• Different data, currency, or character conventions

Legacy systems and their problems

Old technology, computer system, or application such as floppy disks, Windows XP. Nowadays. they may no longer be supported or be available for purchase + modernisation may be expensive and time-consuming.

Local vs remote (SaaS) software

Local - runs on your computer e.g. Notepad, Adobe Photoshop

• One-time fee

• Installed onto computer

• Updates may not always be automatic

• Can only be used on individual’s computer

Remote - accessed through a web browser e.g. Office 365, Google Docs

• Subscription fee

• Automatic updates

• Can be used from any computers via the web

Pros and cons of Software-as-a-Service (SaaS)

Pros

• Employees can operate software from anywhere

• Cheaper

• Fewer support staff needed

• ‘Pay as you go’ subscription model

• Easier to maintain

Cons

• Users have no control over availability of system

• Users have no control over security

• Large-scale data corruption potential risk

Different types of testing

• Static testing: examines documentation and test plans to build the correct system. Uses verification.

• Dynamic testing: tests the code when it is run to check for bugs and make sure the software meets the requirements. Uses verification and validation.

• Alpha testing: tests run by an internal team from the organisation to confirm software works as intended. Lasts for months.

• Beta testing: tests run by people outside of organisation or end-users to get user feedback. Lasts for weeks.

• Black box testing: examines the functionality of an the software without seeing its internal workings. No programming knowledge required.

• White box testing: tests the software by looking at the code’s internal workings. Programming knowledge required.

• User acceptance testing: intended users test the software to see if it meets their needs and operates to their expectations. Validates its functionality in real-world environment.

• Automated testing: uses preconstructed software to compare predicted results with actual results. Can rapidly complete complex tasks.

Types of user documentation and their pros and cons

Manuals (booklet, pamphlets)

• Pros: doesn’t require installation or internet connection

• Cons: can be damaged, can get lost, can become outdated

Online resources (PDFs, website, video)

• Pros: More detailed than manuals, can be updated, search capabilities, live support function

• Cons: Internet required, hard to navigate for inexperienced users

Help files

• Pros: contains general instructions for use, easier to access for inexperienced users

• Cons: doesn’t have search capabilities, can be difficult for inexperienced users, only aids with general errors

Methods of user training and their pros and cons

In-person classes

Pros: Expert on hand, structured learning

Cons: Less personalised, students may become bored, expensive, rigid timeline

Online training

Pros: can be more personalised, expert on hand, structured learning

Cons: more expensive if one-on-one, isolated learning environment

Self instruction

Pros: low-cost, flexible timeline, users can choose area of focus

Cons: can be overwhelming, no guidance, unstructured learning

Causes of data loss

• Hardware / system malfunction

• Human error

• Software corruption

• Malicious software (viruses)

• Natural disasters

Ways to prevent data loss

• Failover system: a secondary system that can become available if the primary system fails

• Redundancy: duplicate of a system’s components and data that can be used as backup

• Removable media: a storage device such as a USB or CD that can store data

• Offsite storage: when data is stored externally through a facility

• Online storage: when data is stored remotely over the internet

Stakeholders

Person with an interest or concern in something, e.g. a business. Examples include: company owners, users, managers, employees.

Methods to obtain requirements from stakeholders

Direct observation: observing the system in use in the real-world

• Pros: get first-hand, unbiased information

• Cons: users may change their behaviour under observation

Interviews: specific questions asked to limited stakeholders

• Pros: get direct and detailed feedback, clarify questions

• Cons: long time to prepare, set up, and conduct

Surveys: general questions asked to many stakeholders

• Pros: time-efficient, can gather a surplus of feedback

• Cons: information limited to the survey and quality of responses may differ

Prototypes

An unfinished plan of the end-product that displays functionality of one or two aspects in order to get feedback from stakeholders.

Importance of iteration

Definition: repetition of a sequence of an operation / instruction until a condition is met. In system development, this can mean prototyping, testing, analysing, and refining the product until all requirements are met. This allows for constant improvement.

Software deployment

• Release: launching a new product

• Update: software file that fixes a problem found after each release = free

• Upgrades: novel functionalities and are cumulative bug fixes = come with a cost

• Patches: temporary fixes that are put in place between full releases - can install drivers, fix bugs

Possible consequences of failing to involve end-user in the design process

• User may be unsatisfied with system

• May accidentally solve another problem / introduce one

• Deal with issues outside of project’s scope

Social and ethical issues associated with the introduction of new IT systems

Robots replacing humans in the workforce, AI algorithms replacing human workers

Define usability

How easily and efficiently a product can be used

Examples of usability issues

• Laptop: battery life too short, bright screen strains eyes

• Phone: screen size too small, not waterproof

• Digital camera: no drag and drop option, small buttons

How to combat usability problems (accessibility)

Braille keyboards, touch screen, voice recognition, text dictation