1.6 system design Flashcards
describe the criteria for evaluating a computer based solution
- requirements: evaluate the solution against the original requirements, all requirements should be met for a solution to be successful
- cost: evaluate the solution against costs which include financial costs, human costs and resource costs, a solution must not exceed any negotiated costs to be successful
- robustness: evaluate the solutions against its test results, a solution should use error trapping and validation methods to successfully robust and reduce the chance of system errors and failures
- usability: evaluate the solution against the ease of use for the end user, a solution should use an intuitive user interface suitable for the end user to be successful
- performance: evaluate the performance of the solution, it should be fully optimised to reduce memory usage, a solution should complete a specific task within a given time frame to be successful
what are the advantages and disadvantage of voice input interface on a hand held device
advantages:
- speech is a natural way to interact, and it is not necessary to use a keyboard or work with a remote control
- no training required for users
- voice is hands-free making it suitable for use in a variety of environments (for example driving)
- suitable for the disabled
- can be used to drive several apps in sequence
- faster than typing on a keyboard
disadvantages:
- even the best speech recognition systems sometimes make errors
if there is noise or some other sound in the room
- regional accents can affect the outcome
- requires data connection to interpret speech and return results
- delivering sensitive information (eg. credit card details could be a security risk)
- only understands certain foreign languages
describe the benefits of speech recognition over a traditional keyboard and mouse
- speeds up text input/ faster than typing
- can be used by someone who is unable to type/ not a skilled typist/ disabled
- allows to simultaneously do other tasks
- takes up less room than a keyboard and mouse ( useful in mobile phones)
what benefits arise if a reliable natural language interface was developed and why is this difficult to achieve
- a natural language interface would need very high processing power
- natural language is used by most people and is very ambiguous and imprecise
what input methods could help users with different physical disabilities
- speech recognition interface (SRI) can be used by someone unable to type
- SRI may have difficulty with background noise/ interface/ can over hear others’ inputs
- SRI may have difficulty with proper nouns/ ambiguity
- foot controlled keyboard/ mouse
- head/ eye movement detector
- oversize keyboard
- braille key overlays
-screen readers can be used together with GUI
what output methods could help users with different physical disabilities
- speech synthesis is useful for people with visual impairment
- speech synthesis may pronounce words incorrectly
- speech synthesis can be annoying/ obtrusive
- speech synthesis may have heavy hardware performance requirements
- screen output can use large/ clear fonts / clear colour contrasts
- braille outputs may be possible - device punches paper with braille characters
what is a command line/ driven interface
- interface where communications uses typed text, probably via a command prompt
- still commonly used for example on servers and network devices
advantages and disadvantage of a command line/ driven interface
advantages:
- some commands can be entered very quickly and precisely once user is proficient/ an expert
- can run on very low spec computers that don’t have good graphical facilities
- can be used over slow connections ( eg. modems as very little data to transfer)
- complex/ unusual commands are often made available that wouldn’t be able available in a gui
disadvantages:
- not easy to guess commands that need to be entered
- can be difficult to learn
- not very attractive interface, rather unfriendly
what is a graphical user interface (GUI)
- interface where communication is via screen elements such as windows, icons, menus, pointers
- may use keyboard shortcuts (eg Ctrl+X for cut)
advantages and disadvantages of a GUI
advantages:
- user friendly, even inexperienced users can often guess what they need to do, no need to remember complex commands
- intuitive/ easier to learn
- windows: can be resized, minimised etc to allow more than 1 window to be viewed at the same time
- icons: small images to represent options , human brain can recognise options, human brain can recognise image quicker than words
- menus: easy to see all options in a pull-down menu
- pointer (mouse pointer): very natural human trait to point at things they want (point and click)
- cut and paste between applications
- similarity/ familiarity between applications
- help, undo, tutorials, customisation
disadvantages:
- ‘can get in the way’, sometimes requires several options to be clicked on to perform a task that would take seconds to type into a command driven interface
- needs a more powerful computer than command drive
what is a menu driver interface
- the user is given a list of options and they make their choice via a simple selection key press
advantages and disadvantages of a menu driven interface
advantages:
- very easy to learn (selection required only)
- limited options, so the user will not get confused
- no need for a keyboard (actual or virtual)
disadvantages:
- only suitable where there are a few/ very limited options
what is a forms dialogue
- the user fills in a form (online) to register their details or used as an advanced search option form
what are the advantages and disadvantages of a forms dialogue
advantages:
- rather like paper form (therefore intuitive)
- there are specific input fields to fill in
- can go back and make changes before the form is submitted
- undo and ‘are you sure?’
-includes validation so only some entries are allowed
- often able to reduce input options using radio buttons, drop down lists
disadvantages:
- good on screen help maybe required
- layout is important
- ensure form is uncluttered
