计算机专业外文翻译.docx

计算机专业外文翻译.docx

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计算机专业外文翻译

ATaleofClouds:

ParadigmComparisonsandSomeThoughtsonResearchIssues*†

LijunMei

TheUniversityofHongKong

Pokfulam,HongKong

ljmei@cs.hku.hk

Abstract

Cloudcomputingisanemergingcomputingparadigm.Itaimstosharedata,calculations,andservicestransparentlyamongusersofamassivegrid.Althoughtheindustryhasstartedsellingcloud-computingproducts,researchchallengesinvariousareas,suchasUIdesign,taskdecomposition,taskdistribution,andtaskcoordination,arestillunclear.Therefore,westudythemethodstoreasonandmodelcloudcomputingasasteptowardidentifyingfundamentalresearchquestionsinthisparadigm.Inthispaper,wecomparecloudcomputingwithservicecomputingandpervasivecomputing.Boththeindustryandresearchcommunityhaveactivelyexaminedthesethreecomputingparadigms.Wedrawaqualitativecomparisonamongthembasedontheclassicmodelof

computerarchitecture.Wefinallyevaluatethecomparisonresultsanddrawupaseriesofresearchquestionsincloudcomputingforfutureexploration.

Keywords:

cloudcomputing,paradigmcomparison

Cloudcomputingisaparadigmthatfocusesonsharingdata

andcomputationsoverascalablenetworkofnodes.Examplesof

suchnodesincludeendusercomputers,datacenters,andWeb

Services.Wetermsuchanetworkofnodesasacloud.An

applicationbasedonsuchcloudsistakenasacloudapplication.

Thisparadigmisincreasinglypopularintheindustry,

whereindustrialleaderssuchasMicrosoft[26],Google

[2],andIBM[5]stronglypromotetheparadigminrecent

years.Anearlyattempttoformulatecloudcomputing

datesbacktoatleast1997[8].However,toourbest

knowledge,theadoptionandpromotionofcloud

computinghasbeenslowuntil2007[9].

Weobservethatthehistoryofearlyindustrial

adoptionsofcloudcomputingsharesomecommon

milestoneswiththatofservicecomputing[4].For

example,ittookservicecomputing[27]alongtime（ten

yearsorso）toreceiveworldwidesupportfromleading

companieslikeIBM,Microsoft[25],BEA,andOracle.

Similarly,ithasbeenmanyyearssincetheearly

formalizationeffort[8]towardcloudcomputing.

Besides,thewideadoptionofacomputingparadigm

usuallydependshighlyonthematurityofsupporting

technologiesandindustryrecognitions.Servicecomputing

hasbecomemuchmorepopularsincethesuccessof

Webservices,althoughaWebserviceisonlyoneofthe

technologiestofulfillthenotionofserviceorientation[4].

Similarly,thedistributedcomputingcommunityhas

pointedoutthatmanydistributedcomputingtechniques

forcloudcomputinghavebeenmature[7][10][11].Many

companiessuchasDellandIBMhavebeguntoship

cloudcomputingmachines[5][10].

Lastbutnottheleast,ineitherservicecomputingor

cloudcomputing,researchdevelopmentslagbehind

industrialadoptions.Forinstance,COSCON,aleading

internationalcontainershipper,hasasuccessfuladoption

ofservicecomputing.Itsuccessfullyusedservice-oriented

architecturetoimprovethebusinessresponsibilityto

customersin2004[3].Yet,researchstudiesinserviceoriented

architecturefromthesoftwareengineering

community[19]arestillinadequate.

DespiteoursurveyovertheInternet,toourbest

knowledge,therearefewarticlestopinpointresearchissues

incloudcomputing.Thiswouldslowdownthe

nextresearchadvances.Wewillalleviatethisproblemin

thepresentpaper.

Inthispaper,weusetheclassiccomputerarchitecture

model[15]toprovideaqualitativecomparisonframework

tocomparecloudcomputingwithpervasivecomputing

andservicecomputing.Thequalitativecomparison

frameworkincludesthreefeatures:

input-output（I/O）,

storage,andcalculation.Foreachfeature,wedrawthe

comparisonusingmultiplecharacteristics.Throughsuch

comparisons,weidentifytheconnectionsbetweencloud

computingandtheothertwocomputingparadigmsfrom

theperspectiveofsoftwareengineering.Basedonthe

connections,wedrawupafewresearchissuesanddiscuss

theminthepapertopromotefutureexploration.

Themaincontributionofthepaperistwofold:

（i）To

ourbestknowledge,weprovidethefirstqualitative

comparisononcloudcomputing,servicecomputing,and

pervasivecomputing.（ii）Wepresentaseriesofresearch

issuesincloudcomputingontopofthecomparison

framework.Theseissuespromotefutureexplorations.

Therestofthepaperisorganizedasfollows:

Section2

presentsthepreliminariesofcloudcomputing,service

computing,andpervasivecomputing.Section3introduces

ourqualitativeframeworktocomparetheabove

threecomputingparadigmsandpresentoureffortsto

identifyresearchissuesincloudcomputing.Finally,we

reviewrelatedworkinSection4anddrawaconclusionin

Section5.

2.Preliminaries

Thissectionreviewsthepreliminariesofcloud

computing,servicecomputing,andpervasivecomputing.

2.1.Cloudcomputing

AswehaveintroducedinSection1,acomputingcloud

isamassivenetworkofnodes.Thus,scalabilityshouldbe

aqualityfeatureofthecomputingcloud.Ithasatleast

twodimensions,namelyhorizontalcloudscalabilityand

verticalcloudscalability（adaptedfrom[9]）.

􀁺Horizontalcloudscalabilityistheabilitytoconnect

andintegratemultiplecloudstoworkasonelogical

cloud.Forinstance,acloudprovidingcalculation

services（calculationcloud）canaccessacloud

providingstorageservices（storagecloud）tokeep

intermediateresults.Twocalculationcloudscanalso

integrateintoalargercalculationcloud.

􀁺Verticalcloudscalabilityistheabilitytoimprovethe

capacityofacloudbyenhancingindividualexisting

nodesinthecloud（suchasprovidingaserverwith

morephysicalmemory）orimprovingthebandwidth

thatconnectstwonodes.Inaddition,tomeetincreasing

marketdemand,anodecanbegraduallyupgradedfrom

asinglepowermachinetoadatacenter.

Scalabilityshouldbetransparenttousers.Forinstance,

usersmaystoretheirdatainthecloudwithouttheneedto

knowwhereitkeepsthedataorhowitaccessesthedata.

Forsimplicity,wewillrefertohorizontalandvertical

cloudscalability,respectively,ashorizontalscalability

andverticalscalabilityinthispaper.

2.2.Servicecomputing

Servicecomputing（orservice-orientedcomputing）is

anemergingparadigmtomodel,create,operate,and

managebusinessservices.Inthisparadigm,services

publishthemselvesinpublicregistries,discoverpeer

services,andbindtothelatterservicestoformservice

compositionsusingstandardizedprotocols[6].Tocreatea

servicecomposition,engineersmayuseaspecification,

suchasWS-BPEL[30],tomodelthecollaborativeneed

inworkflows.Tocarryoutindividualworkflowsteps,

softwaredevelopersmayuseWebservices,themost

popularwaytofulfillservice-orientedarchitectureinthe

industry.Asetofservice-orientedapplicationsoverthe

Webservicesthuscreatesanetworkofservices.

Webrieflydescribeaservice-orientednetwork[18]to

facilitatethecomparisonintherestofthepaper.An

elementinsuchanetworkisaserviceregistry,service

consumer,orserviceprovider.Aserviceprovider

registersitselfinaserviceregistry.Aserviceconsumer

firstdiscoverstheservicefromaregistry,andthenbinds

totheservice.Aserviceprovidermayregisteritselfto

morethanoneregistry.Aregistrymayalsoassociateits

registeredservicestootherregistries,andactsasaservice

itself.Suchatreatmentonaregistryprovidesageneric

viewamongelementsinservice-orientedmodeling.

2.3.Pervasivecomputing

Pervasivecomputing（orubiquitouscomputing）[23][24]

isanotheremergingcomputingparadigm.Software（often

referredaspervasivesoftware）canbeembeddedina

constantlychangingcomputingenvironment.Therefore,

pervasivesoftwareusersdonotneedtobeconcerned

abouthowtoadjustthesoftwaretoadapttothe

surroundingcomputingenvironment.Awell-developed

environmentwillenableuserstousepervasivesoftware

everywherewithoutextraeffort.

Tounderstandandreacttoauser,applicationsuse

environmentalfeatures,knownascontexts,extensively.

Sensorscancapturethesecontexts.Toallowubiquitous

3supporttoendusers,smartsensorsareplacedaround

userstopreservedifferentinformation,suchasthe

locations,contexts,anduser-relevantdata.

Sensors,mobilephonesandPDAs,desktopcomputer,and

serversareinterconnectedlogicallytoformanapplication.

SupposeanomadicuseratthetopleftcornerofFigure2

movesfromusingalaptoptousingadesktopcomputer.

ThelaptopandthedesktopcomputerbothserveasUI

portalstothetuplespacemaintainedbythepervasive

software.Theremarkedinformationfromvariousdisplay

portals（suchasthePDAsontheright-handpart）may

needadapting.Forexample,adesktopcomputermaybe

equippedwithahigh-definitionwebcam.Thus,a

presentationdisplayportalmaydisplaythecontentswith

acameraimagekeptinthetuplespaceoftheapplication

whenusingalaptop.

3.Comparisonofcloud,service,and

pervasivecomputingparadigms

Thissectionpresentsaqualitativecomparisonamong

thecloud,service,andpervasivecomputingparadigms.

Manyresearchersconsidercloudcomputingasderived

fromgridcomputing[12]andhaveprovidedmany

comparisonsbetweenthem[21].Toidentifymoreissues

forcloudcomputing,wechoosetocompareitwith

servicecomputingandpervasivecomputingforthe

followingreasons.Servicecomputingisusefulin

modelingfunctionalityandprovidingflexibleservices.

Pervasivecomputingenablesuserstousesoftware

everywhereandprovidesself-adaptivecapacitytothe