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:
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.
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.
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.
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.
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.
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
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