Human Computer Interface Unit-5

UNIT-V

Software tools

Specification Methods

• Design requires a good notation to record and discuss alternate possibilities:

• The default language for specifications in any field is  natural language, e.g., English

• Communication medium, e.g., sketchpad, or blackboard

• Natural-language specifications tend to be:

• lengthy

• vague

• ambiguous

• Therefore, often are difficult to prove:

• correct

• consistent

• complete

• Backus-Naur Form (a.k.a. Backus Normal Form or BNF)

• high-level components are described as non terminal

• specific strings are described as terminals

• Grammars Example

<Telephone book entry>:= <Name><Telephone number>

<Name> ::=< Last name>, <First name>

<Last name> ::=< string>

<First name> ::=< string>

<String> ::=< character>|<character><string>

<Character>:= A|B|C|D|E|F|G|H|I|J|K|L|M|N|O|P|Q|R|S|T|U|V|W|X|Y|Z

<Telephone number>:= (<area code>) <exchange>-<local number>

<Area code> ::=< digit><digit><digit>

<Exchange> ::=< digit><digit><digit>

<Local number>:= <digit><digit><digit><digit><digit>:= 0|1|2|3|4|5|6|7|8|9

• Examples of acceptable entries

-WASHINGTON, GEORGE (301)555-1234

-BEEF, STU (726)768-7878

-A, Z (999)111-1111

• Multiparty grammars

<Session> ::=< U: Opening><C: Responding>

<U: Opening>:= LOGIN <U: Name>

<U: Name> ::=< U: string>

<C: Responding>:= HELLO [<U: Name.]

U: User C: Computer

• Multiparty grammars are effective for text oriented command sequences

• Transition Diagram

• a set of nodes that represents system states and a set of links between the nodes that represents possible transitions

• State Charts

Interface-Building Tools:

Features of Interface-Building Tools.

• User Interface Independence

• Separate interface design from internals

• Enable multiple user interface strategies

• Enable multiple platform support

• Establish user interface architect role

• Enforce standards

• Methodology & Notation

• Develop design procedures

• Find ways to talk about design

• Create project management

• Rapid Prototyping

• Try out ideas very early

• Test, revise, test, revise, ...

• Engage end users, managers, and others
  

• Software Support

• Increase productivity

• Offer some constraint & consistency checks

• Facilitate team approaches

• Ease maintenance

User interface mockup tools

• Examples

• Paper and pencil

• Word processors

• Slide-show software

• Macromedia Director, Flash mix, or Dreamweaver

• Visual Editing

• Microsoft Visual Studio

• Borland J Builder

Finding the right tool is a tradeoff between six main criteria:

• Part of the application built using the tool.

• Learning time

• Building time

• Methodology imposed or advised

• Communication with other subsystems

• Extensibility and modularity

Interaction Devices- Keyboard Layouts QWERTY layout

• 1870 Christopher Latham Sholes

• good mechanical design and a clever placement of the letters that slowed down the users enough that key jamming was infrequent

• put frequently used letter pairs far apart, thereby increasing finger travel distances

Dvorak layout

– 1920

• reduces finger travel distances by at least one order of magnitude
  

• Acceptance has been slow despite the dedicated efforts of some devotees

• it takes about 1 week of regular typing to make the switch, but most users have been unwilling to invest the effort

ABCDE style

• 26 letters of the alphabet laid out in alphabetical order no typists will find it easier to locate the keys

Additional keyboard issues

• IBM PC keyboard was widely criticized because of the placement of a few keys

• backslash key where most typists expect SHIFT key

• placement of several special characters near the ENTER key

• Number pad layout

• wrist and hand placement

Keys

• 1/2 inch square keys

• 1/4 inch spacing between keys

• slight concave surface

• matte finish to reduce glare finger slippage

• 40- to 125-gram force to activate

• 3 to 5 millimeters displacement

• tactile and audible feedback important

• certain keys should be larger (e.g. ENTER, SHIFT,CTRL)

• some keys require state indicator, such as lowered position or light indicator (e.g. CAPS LOCK)

• key labels should be large, meaningful, permanent

• some "home" keys may have additional features, such as deeper cavity or small raised dot, to help user locate their fingers properly (caution - no standard for this)

Function keys

• users must either remember each key's function, identify them from the
  

screen's display, or use a template over the keys in order to identify them properly

• can reduce number of keystrokes and errors

• meaning of each key can change with each application placement on keyboard can affect efficient use

• special purpose displays often embed function keys in monitor bezel

• lights next to keys used to indicate availability of the function, or on/off status

• Typically, simply labeled F1, F2, etc, though some may also have meaningful labels, such as CUT, COPY, etc.

• frequent movement between keyboard home position and mouse or function keys can be disruptive to use

• alternative is to use closer keys (e.g. ALT or CTRL) and one letter to indicate special function

Cursor movement keys

• up, down, left, right

• some keyboards also provide diagonals

• best layout is natural positions

• inverted-T positioning allows users to place their middle three fingers in a way that reduces hand and finger movement

• cross arrangement better for novices than linear or box

• typically include typeamatic (auto-repeat)feature

• important for form-fill-in and direct manipulation

• Other movements may be performed with other keys, such as TAB, ENTER, HOME, etc.

Keyboard and keypads for small devices

• Wireless or foldable keyboards

• Virtual keyboards

• Cloth keyboards

• Soft keys

• Pens and touch screens
  

Pointing Devices

Pointing devices are applicable in six types of interaction tasks:

1. Select:

• User chooses from a set of items.

• Used for traditional menu selection, identification of a file in a directory, or marking of a part in an automobile design.

2. Position:

• User chooses a point in a one-, two-, three-, or higher-dimensional space

• Used to create a drawing, to place a new window, or to drag a block of text in a figure.

3. Orient:

• User chooses a direction in a two-, three-, or higher-dimensional space.

• Direction may simply rotate a symbol on the screen, indicate a direction of motion for a spaceship, or control the operation of a robot arm.

4. Path:

• User rapidly performs a series of position and orient operations.

• May be realized as a curving line in a drawing program, the instructions for a cloth cutting machine, or the route on a map.

5. Quantify:

• User specifies a numeric value.

• Usually a one-dimensional selection of integer or real values to set parameters, such as the page number in a document, the velocity of a ship, or the amplitude of a sound.

6. Text:

• User enters, moves, and edits text in a two-dimensional space. The

• Pointing device indicates the location of an insertion, deletion, or change.

• More elaborate tasks, such as centering; margin setting; font sizes; highlighting, such as boldface or underscore; and page layout.

Direct-control pointing devices light pen

• enabled users to point to a spot on a screen and to perform a select, position, or another task

• it allows direct control by pointing to a spot on the display

• incorporates a button for the user to press when the cursor is resting on the desired spot on the screen

• light pen has three disadvantages: users' hands obscured part of the screen, users had to remove their hands from the keyboard, and users
  

had to pick up the light pen

Touch screen

• allows direct control touches on the screen using a finger

• early designs were rightly criticized for causing fatigue, hand- obscuring-the- screen, hand-off-keyboard, imprecise pointing, and the eventual smudging of the display

• lift-off strategy enables users to point at a single pixel

• the users touch the surface

• then see a cursor that they can drag around on the display

• when the users are satisfied with the position, they lift their fingers off the display to activate

• can produce varied displays to suit the task

• are fabricated integrally with display surfaces

Tablet PCs and Mobile Devices:

• Natural to point on the LCD surface

• Stylus

• Keep context in view

• Pick up & put down stylus

• Gestures and handwriting recognition

Indirect pointing devices

• mouse

• the hand rests in a comfortable position, buttons on the mouse are easily pressed, even long motions can be rapid, and positioning can be precise

• trackball

• usually implemented as a rotating ball 1 to 6 inches in diameter that moves cursor

• joystick

• are appealing for tracking purposes

• Graphics tablet

– A touch-sensitive surface separate from the screen

• Touchpad

• built-in near the keyboard offers the convenience and precision of a touch screen while keeping the user's hand off the display surface
  

• Human-factors variables

• speed of motion for short and long distances

• accuracy of positioning

• error rates

• learning time

• user satisfaction

• Other variables

• cost

• durability

• space requirements

• weight

• left- versus right-hand use

• likelihood to cause repetitive-strain injury

• compatibility with other systems

Comparison of pointing devices

• Some results

• direct pointing devices faster, but less accurate

• graphics tablets are appealing when user can remain with device for long periods without switching to keyboard

• mouse is faster than isometric joystick

• for tasks that mix typing and pointing, cursor keys a faster and are preferred by users to a mouse

• muscular strain is low for cursor keys

• Fit’s Law

• Index of difficulty = log2 (2D /W)

• Time to point = C1 + C2 (index of difficulty)

• C1 and C2 and constants that depend on the device

• Index of difficulty is log2 (2*8/1) = log2(16) = 4bits

• A three-component equation was thus more suited for the high-precision pointing task:

• Time for precision pointing = C1 + C2 (index of difficulty) + C3 log2 (C4 /W)
  

Novel devices

• Foot controls

• Eye-tracking

• Multiple-degrees-of-freedom devices

• Data Glove

• Hap tic feedback

• Bimanual input

• Ubiquitous computing and tangible user interfaces

• Handheld devices

Speech and auditory interfaces

• Speech recognition still does not match the fantasy of science fiction:

• demands of user's working memory

• background noise problematic

• variations in user speech performance impacts effectiveness

• most useful in specific applications, such as to benefit handicapped users

• Discrete word recognition

• recognize individual words spoken by a specific person; can work with 90- to98- percent reliability for 20 to 200-wordvocabularies

• Speaker-dependent training, in which the user repeats the full vocabulary once or twice

• Speaker-independent systems are beginning to be reliable enough for certain commercial applications

• been successful in enabling bedridden, paralyzed, or otherwise disabled people

• also useful in applications with at least one of the following conditions:

• speaker's hands are occupied

• mobility is required

• speaker's eyes are occupied

• harsh or cramped conditions preclude use of keyboard

• voice-controlled editor versus keyboard editor

• lower task-completion rate

• lower error rate

• use can disrupt problem solving

• Continuous-speech recognition

• Not generally available:

• difficulty in recognizing boundaries between spoken words
  

• normal speech patterns blur boundaries

• many potentially useful applications if perfected

• Speech store and forward

• Voice mail user scan

• receive messages

• replay messages

• reply to caller

• forward messages to other users, delete messages

• archive messages

• Systems are low cost and reliable.

• Voice information systems

• Stored speech commonly used to provide information about tourist sites, government services, after-hours messages for organizations

• Low cost

• Voice prompts

• Deep and complex menus frustrating

• Slow pace of voice output, ephemeral nature of speech, scanning and searching problems

• Voicemail

• Handheld voice recorders

• Audio books

• Instructional systems

• Speech generation

• Michaels and Wiggins (1982) suggest that speech generation is "frequently preferable" under these circumstances:

• The message is simple.

• The message is short.

• The message will not be referred to later.

• The message deals with events in time.
  

• The message requires an immediate response.

• The visual channels of communication are overloaded.

• The environment is too brightly lit, too poorly lit, subject to severe vibration, or otherwise unsuitable for transmission of visual information.

• The user must be free to move around.

• The user is subjected to high G forces or anoxia

Audio tones, audio libation, and music

• Sound feedback can be important:

• to confirmations

• offer warning

• for visually impaired users

• music used to provide mood context, e.g. in games

• can provide unique opportunities for user, e.g. with simulating various musical instruments

Displays – Small and Large

• The display has become the primary source of feedback to the user from the computer

• The display has many important features, including:

• Physical dimensions (usually the diagonal dimension and depth)

• Resolution (the number of pixels available)

• Number of available colors, color correctness

• Luminance, contrast, and glare

• Power consumption

• Refresh rates (sufficient to allow animation and video)

• Cost

• Reliability

Usage characteristics distinguish displays:

• Portability

• Privacy

• Saliency

• Ubiquity

• Simultaneity Display technology

• Monochrome displays

• are adequate, and are attractive because of their lower cost

• RGB shadow-mask displays
  

• small dots of red, green, and blue phosphors packed closely

• Raster-scan cathode-ray tube(CRT)

• electron beam sweeping out lines of dots to form letters

• refresh rates 30 to 70 per second

• Liquid-crystal displays(LCDs)

• voltage changes influence the polarization of tiny capsules of liquid crystals

• flicker-free

• size of the capsules limits the resolution

• Plasma panel

• rows of horizontal wires are slightly separated from vertical wires by small glass-enclosed capsules of neon-based gases

• Light-emitting diodes(LEDs)

• certain diodes emit light when a voltage is applied

• arrays of these small diodes can be assembled to display characters

• Electronic ink

• Paper like resolution

• Tiny capsules with negatively and positively charged particles

• Braille displays

• Pins provide output for the blind

• Large displays

• Informational wall displays

• Interactive wall displays

• Multiple desktop displays

• Heads-up and helmet mounted displays

• A heads-up display can, for instance, project information on a partially silvered widescreen of an airplane or car

• A helmet/head mounted display (HMD) moves the image with the user

• 3D images

Mobile device displays

• Currently mobile devices used for brief tasks, except for game playing

• Optimize for repetitive tasks

• Custom designs to take advantage of every pixel

• Data Lens allows compact overviews
  

• Web browsing difficult

• Okay for linear reading, but making comparisons can be difficult

Animation, image, and video

• Accelerated graphics hardware

• More information shared and downloaded on the web

• Scanning of images and OCR

• Digital video

• CDROMS and DVDs

• Compression and decompression through MPEG

• Computer-based videoconferencing

Printers

• Important criteria for printers:

• Speed

• Print quality

• Cost

• Compactness

• Quiet operation

• Use of ordinary paper (fan folded or single sheet)

• Character set

• Variety of typefaces, fonts, and sizes

• Highlighting techniques (boldface, underscore, and soon)

• Support for special forms (printed forms, different lengths, and soon)

• Reliability

• dot-matrix printers

• print more than 200 characters per second, have multiple fonts, can print boldface, use variable width and size, and have graphics capabilities

• inkjet printers

• offer quiet operation and high-quality output

• thermal printers or fax machines

• offer quiet, compact, and inexpensive output on specially coated papers
  

• laser printers

• operate at 30,000 lines per minute

• color printers

• allow users to produce hardcopy output of color graphics, usually by an inkjet approach with three colored and black inks

• photographic printers

• allow the creation of 35-millimeter or larger slides (transparencies) and photographic prints