Bandwidth - Human Resource - Lecture Slides, Slides of Human Resource Management

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bandwidth, latency and jitter

send

receive

time

bandwidth

how much

latency

how long

jitter

how variable

design implications

• bandwidth ⇒ think about download time

– e.g. 100K image: 1 sec – broadband, 18 secs – 56K modem

– save graphics in appropriate format and size

– reuse the same graphics

• in the browser cache after first load

• connection time

– one big file may be better then several small ones

• beware of ‘fit on one screen’ rule – scrolling is fast!

• think before breaking big graphic into bits

• latency ⇒ think about feedback

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WAP - web on the phone

• very small screen

– scrolling painful ⇒ small ‘pages’

– GSM connection slow ⇒ big chunks

• WML (wireless mark-up language)

– content delivered in ‘stacks’ of ‘cards’

– cards are the ‘pages’ the user views

– but navigation within the stack fast

errata: book says stacks of ‘notes’, cards is correct

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syuh how gtw hsio i ert ag ty ghn ty we ghty chdi qw oatyf wet dfla ght a

syuh how gtw hsio i ert ag ty ghn ty we ghty chdi qw oatyf wet dfla ght a

syuh how gtw hsio i ert ag ty ghn ty we ghty chdi qw oatyf wet dfla ght a

syuh how gtw hsio i ert ag ty ghn ty we ghty chdi qw oatyf wet dfla ght a

server sends whole stack

using WAP protocol

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syuh how gtw hsio i ert ag ty ghn ty we ghty chdi qw oatyf wet dfla ght a

syuh how gtw hsio i ert ag ty ghn ty we ghty chdi qw oatyf wet dfla ght a

syuh how gtw hsio i ert ag ty ghn ty we ghty chdi qw oatyf wet dfla ght a

syuh how gtw hsio i ert ag ty ghn ty we ghty chdi qw oatyf wet dfla ght a

syuh how gtw hsio i ert ag ty ghn ty we ghty chdi qw oatyf wet dfla ght a

syuh how gtw hsio i ert ag ty ghn ty we ghty chdi qw oatyf wet dfla ght a

syuh how gtw hsio i ert ag ty ghn ty we ghty chdi qw oatyf wet dfla ght a

syuh how gtw hsio i ert ag ty ghn ty we ghty chdi qw oatyf wet dfla ght a

syuh how gtw hsio i ert ag ty ghn ty we ghty chdi qw oatyf wet dfla ght a

syuh how gtw hsio i ert ag ty ghn ty we ghty chdi qw oatyf wet dfla ght a

syuh how gtw hsio i ert ag ty ghn ty we ghty chdi qw oatyf wet dfla ght a

navigation within stack fast

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server stores ‘stacks’ of cards

N.B. larger screens

and faster

connections mean

WML giving way to

small HTML pages

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syuh how gtw hsio i ert ag ty ghn ty we ghty chdi qw oatyf wet dfla ght a

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static web content

medium and message

text, graphics, movies and sound

text

• text style

– generic styles universal: serif, sans, fixed, bold , italic

– specific fonts too, but vary between platforms

– cascading style sheets (CSS) for fine control

… but beware older browsers and fixed font sizes

– colour … often abused!

• positioning

– easy .. left, right justified or centred

– precise positioning with DHTML … but beware platforms …

– screen size

• mathematics … needs special fonts, layout, … arghhhh

graphics

• use with care …

– N.B. file size and download time …

this image = 1000 words of text

– affected by size, number of colours, file format

– backgrounds … often add little, hard to read text

• speeding it up

– caching – reuse same graphics

– progressive formats:

• image appears in low res and gets clearer

icons

• on the web just small images

– for bullets, decoration

– or to link to other pages

– lots available!

• design … just like any interface

– need to be understood

– designed as collection to fit …

• under construction

– a sign of the inherent incompleteness of the web

– or just plain lazy ??