Distributed Interaction C.W. Johnson, Univ ersit y of Glasgo w, Glasgo w, G12 8QQ. Scotland. johnson@dcs.gla.ac.uk, h ttp://www.dcs.gla .a c.uk/ � johnso n Octob er 2001 c CS-1Q: HCI (Lecture 5) � C.W. Johnson, 2001 1
Distributed Interaction Infrastructure issues: � - Internet p roto cols, the W eb and b ey ond. Usabilit y issues: � - b ro wsing and task directed sea rch; - info rmation saturation and redundancy; - dela ys, unp redictabilit y and securit y . c CS-1Q: HCI (Lecture 5) � C.W. Johnson, 2001
Distributed Interaction Ac kno wledgemen t: h ttp://www.cs.b ell-labs.com/who/c hes/map/gallery/isp-ss.gif The Internet: � - 1971 23 hosts; 1980 100 hosts; 1990 1,000,000... c CS-1Q: HCI (Lecture 5) � C.W. Johnson, 2001
Infrastructure Issues What do w e need to connect machines: � - an addressing scheme (`where a re y ou out there?'); - transfer p roto cols (`ho w much info can I pass y ou?'). Internet Proto col underlies it all: � - IP address of sender and recipient plus info rmation; - routers read the address of pack ets and fo rw a rd them on. c CS-1Q: HCI (Lecture 5) � C.W. Johnson, 2001
Infrastructure Issues On top of IP w e can build: � - T ransmission Control Proto col - reliable connections; - User Datagram Proto col - unreliable messages. On top of TCP/IP w e can build: � - ftp - �le transfer p roto col; - SMTP - mail transfer p roto col; - NNTP - net news transfer p roto col; - http - hyp ertext transfer p roto col. c CS-1Q: HCI (Lecture 5) � C.W. Johnson, 2001
Infrastructure Issues The W eb: � - CERN and Tim Berners-Lee (among others); - 1993 Nat. Centre fo r Sup ercomputer Applications' Mosaic; - Netscap e commercial successo r then Microsoft IE. Rememb ers: � - W eb is not only fo rm of hyp ertext system; - W eb is not the same as the Internet... Many other ideas and mo dels: � - T ed Nelson's Xanadu transclusion ideas; - `The Grid', E-Science - lots of hyp e... c CS-1Q: HCI (Lecture 5) � C.W. Johnson, 2001
Usabilit y Issues: Accessibilit y So what do es distribution buy users? � Can access remote resources: � - computational resources; - info rmation resources; - human resources (next lecture). Tw o p rinciple mo des of activit y: � - b ro wsing, undirected, ad ho c and opp o rtunistic; - direct sea rch, clea r task, often time limited. c CS-1Q: HCI (Lecture 5) � C.W. Johnson, 2001
Usabilit y Issues: Bro wsing As designers, can y ou attract user? � - avoid scrolling and gratuitous animation; - banner advertising can b e o�-putting; - high do wnload latencies (see later). Dw ell time is a k ey issue: � - examine server logs fo r abandoned requests; - ma y need remote usabilit y testing. c CS-1Q: HCI (Lecture 5) � C.W. Johnson, 2001
Usabilit y Issues: Directed Sea rch T ask directed interaction. � Action Input devices Specification Intentions Execution User Bridge Physical System Interface display Interpretation Evaluation Evaluation Bridge Info rmation retrieval: � 1. F o rm intention to �nd info rmation; 2. T ranslate intention into query language; 3. Evaluate results of sea rch request; 4. If not found, refo rm intention o r query ... c CS-1Q: HCI (Lecture 5) � C.W. Johnson, 2001
Usabilit y Issues: Info rmation Saturation Ma y get a huge numb er of hits; � - few of them ma y actually b e relevant to y our task. Sea rch on D VD gives 6 million+ hits. � c CS-1Q: HCI (Lecture 5) � C.W. Johnson, 2001
Usabilit y Issues: Info rmation Saturation Precision: � number of r el ev ant hits total number of documents r etur ned Recall: � number of r el ev ant hits total number of r el ev ant documents in col l ection Relevance feedback: � - user indicates which `hits' a re relevant; - system uses this to imp rove next sea rch. Rememb er also the p roblem of sea rch IN a page. � c CS-1Q: HCI (Lecture 5) � C.W. Johnson, 2001
Usabilit y Issues: Redundancy Multiple sources of info rmation: � - if one server fails then there a re others; - camera b ought in Glasgo w but drivers in Singap o re. Increase in global comp etition: � - B2B (business to business) transactions; - if y our site fails I can �nd another. Usabilit y is suddenly very imp o rtant. � 2 click techniques (eg Amazon). � c CS-1Q: HCI (Lecture 5) � C.W. Johnson, 2001
Usabilit y Issues: Dela ys Distributed systems sp eed interaction: � { cacheing holds info rmation close to p oint of use; { mirro r sites replicate a server close to user. So where do es a w eb page come from? � Alw a ys try to minimise �le sizes. � Avoid gratuitous graphics and animations. � Give users w a rning ab out `exp ensive' resources. � Myth of the In�nitely F ast Machine. � c CS-1Q: HCI (Lecture 5) � C.W. Johnson, 2001
Usabilit y Issues: P o rtabilit y and Java P o rtabilit y: � - don't just move data b et w een machines; - also move co de and applications. Lo cal execution of remote co de: � - Java b yteco de do wnloaed from w eb; - Java virtual machine executes on client; - securit y issues?? c CS-1Q: HCI (Lecture 5) � C.W. Johnson, 2001
Usabilit y Issues: P o rtabilit y and Java A WT mak es interface lo ok lik e host machine. � Swing mak es interface lo ok same on all machines. � c CS-1Q: HCI (Lecture 5) � C.W. Johnson, 2001
Usabilit y Issues: Unp redictabilit y Summa ry: � - don't kno w where y our info rmation is coming from; - don't kno w where co de is b eing executed. Loading on remote servers va ries: � - with time of the da y (US da ylight hours); - with p ro cess p ro�le (lots of computations?); - with mirro r/cacheing supp o rt. W eb p erfo rmance is very unp redictable. � c CS-1Q: HCI (Lecture 5) � C.W. Johnson, 2001
Usabilit y Issues: Unp redictabilit y Solutions to unp redictabilit y . � Give users an idea of the p ossible dela y: � - indicate �le sizes fo r remote resources. Indicate qualit y of the resource: � - thumb-nail images of videos sho w p ro duction qualities. Alternatively , mak e all dela ys p redictable: � - technically not easy to do but some suggest adding dela ys; - everything w ould tak e 5 minutes... - users w ould develop gies ; c oping str ate - slightly w acky - not sure... c CS-1Q: HCI (Lecture 5) � C.W. Johnson, 2001
Usabilit y Issues: Securit y Users often don't kno w ab out this. � Op enly sha re passw o rds. � Use the same passw o rd everywhere 8( � So cial issues - do y ou trust the w eb? � c CS-1Q: HCI (Lecture 5) � C.W. Johnson, 2001
Final Caveats US census 1990: � - total p opulation 230,445,777; - 198,600,798 only sp eak English; - 31,844,979 p rima rily non-English sp eaking. V ery W ell W ell Not W ell Not at All 17,862,477 7,310,301 4,826,958 1,845,243 T able 1: 1990 US Census Data for Self-Rep orted Abilit y in English US census 2000: � - 54,000,000 (51%) of households had 1 o r mo re computers; - this w as an increase of +42% from 1998. US census 2000: � - 45,000,000 (42%) use Internet at home; - it w as 26% in 1998 and 18% in 1997. Don't get ca rried a w a y b y gro wth of Internet! � c CS-1Q: HCI (Lecture 5) � C.W. Johnson, 2001
Summa ry Infrastructure issues: � - Internet p roto cols, the W eb and b ey ond. Usabilit y issues. � Accessibilit y . � Bro wsing and task directed sea rch. � Info rmation saturation and redundancy . � P o rtabilit y , Java and RMI. � Dela ys, unp redictabilit y and securit y . � c CS-1Q: HCI (Lecture 5) � C.W. Johnson, 2001
F urther Reading A lot of detailed material to cover. � Shneiderman on: � - resp onse time - pp. 351-366; - the w eb - pp. 551-579. c CS-1Q: HCI (Lecture 4) � C.W. Johnson, 2001
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