A Visual Programming Environment for Developing Co

AVisualProgrammingEnvironmentforDevelopingComplexGridApplicationsAntonioCongiusta1,2,DomenicoTalia1,2,andPaoloTrunfio21ICAR-CNR,InstituteoftheItalianNationalResearchCouncil,ViaP.Bucci,41c,87036Rende,[e-mail]2DEIS-UniversityofCalabria,ViaP.Bucci,41c,87036Rende,Italy{talia,trunfio}@deis.unical.it1IntroductionGridsarereceivingevenmoreattentionbyasignificantnumberofscientific,indus-trial,andeconomicalbodies,thankstotheircapabilitytoenablecollaborations,evencross-organizational,basedonlargescaleresourcesharingandperformanceorienta-tion.InthelatestyearsGridsresearchersandprofessionalshavebeenconcernedwiththedevelopmentofaseriesofexperimentsanddemonstrationsaimedatshowingbasicGridfeaturesandpotentials.LargescaleGridsweredeployedtosolvecomputa-tionalordataintensiveproblemsaswellastoperformcomplexsimulations.Pres-ently,Gridsarewidelyrecognizedasthenextgenerationcomputingarchitecture,thenaturalevolutionoftheWebtowardsthedeliveryofcomputingpower,information,andknowledge.Now,Gridcommunityeffortsarefocusedtomakethattechnologyrobust,reliable,andavailabletothoseinterestedinadoptingit.TherecentinvolvementofcompanieslikeIBM,Sun,andMicrosoftisaclearsymptomoftherelevancethematterisgoingtoassumeinthenearfuture.Belongthistrend,providinghigh-levelenvironmentsandadvancedinstrumentsabletosupportendusersanddevelopers,isofmainimportancetoexploremanyoftheGridrelatedbenefitsnotyetfullyexploited.IntheGriderapeoplehavenottoworryabouttheacquisitionofpowerfulcom-putersorexpensiveinstruments,butratherthekeyaspectisthecapabilityofeffec-tivelyexploitsharedresourcesthroughhighlevelenvironmentsprovidingtheneededabstractionsandfacilities.Indeed,todaythisscenarioisstillnotrealisticduetore-searchandtechnologicalchallengesthatmustbefaced,butitshouldleadscientistsandprofessionalstoprovidemoreabstracttechniquesandtoolsforsupportingGridcomputing.MostproblemsaddressedbyGridsarenotsimplysolvedthroughtheexecutionofaspecificadhoc“program”,butoftenrequireseveralsoftwaremodules,mostlikelyinteractingeachothers,torunseparatelyand/orconcurrentlyoveragivensetofin-puts.DuringacertainperiodoftimeGridPortalshavebeenthemostadvancedin-strumentforthesolutionofthiskindofproblems.Buttheyrepresentstillalimitedprogrammingapproachandareoftentailoredtospecificapplicationdomains.Tilltodaynotmuchworkhasbeendonetobuildhigh-leveldesignfacilitiesforcomplexGridapplicationsinwhichmanyprogramsanddatasetsareinvolved.Thisclassofapplicationsarequitecommoninseveraldomains,suchasknowledgeman-agement,computationalscience,ande-business;inadditiontheysharecommontraitswithsoftwarecomponentbasedapplications.Softwarecomponenttechnologyisnowastandardpartofmanysoftwaredesignpractices.MicrosoftCOMandmuchof.NET[1]arebasedoncomponentconcepts,aswellasEnterpriseJavaBeans[2],thatisanotherimportanttechnologyforbuildinglargescalee-commerceapplications.Asoftwarecomponentmodelisasystemforassemblingapplicationsfromsmallerunitscalledcomponents.Thesystemdefinesasetofrulesthatspecifythepreciseexecutionenvironmentprovidedtoeachcompo-nent,therulesofbehavior,andspecialdesignfeaturescomponentsmayhave.Acom-ponentisthennothingmorethananobject(orcollectionofobjects)thatobeytherulesofthecomponentarchitecture.Acomponentframeworkisthesoftwareenvi-ronmentthatprovidesthemechanismstoinstantiatecomponents,composeandusethemtobuildapplications.ThesoftwarecomponentmodelcanbeeffectivelyusedinGridapplicationsintegratinglegacycodeandnewsoftwaremodules.Inthischapterwepresentahigh-levelGridprogrammingenvironmentthatsharessomecommonfeatureswiththesoftwarecomponentparadigm.ThesystemwediscusshereisVEGA-VisualEnvironmentforGridApplications.VEGAprovidesaunifiedenvironmentcomprisingservicesandfunctionalitiesrangingfrominformationanddiscoveryservicestovisualdesignandexecutionfacilities.VEGAwasdesignedandimplementedtosupportusersinthedesignofdata-intensiveGridapplicationsaspartoftheKnowledgeGrid[6],asoftwareinfrastructurefordevelopingknowledgedis-coveryapplications.Howeveritshigh-levelfeaturesmakeitusefulinthedevelopmentofalargeclassofGridapplications.Theremainderofthechapterisorganizedasfollows.Section2presentsthedesignaspectsandthemainfeaturesofVEGA.Section3introducesthevisuallanguageusedtodesignanapplicationinVEGA.Section4illustratesthearchitectureoftheenvi-ronmentandSection5goesmoredeeplyintosomeimplementationaspects.SeveralenhancementsandadditionalfeaturesunderdevelopmentarepresentedinSection6,where“openissues”arediscussed.Section7presentstwocasestudiesandSection8discussessomeofthemajorrelatedprojects.Finally,Section9concludesthechapter.2MainFeaturesandRequirementsThemaingoalofVEGAistoofferasetofvisualfunctionalitiesthatgivetheusersthepossibilitytodesigncomplexsoftware,suchascomplexsolvingenvironmentsandknowledgediscoveryapplications,startingfromaviewofthepresentGridstatus(i.e.,availablenodesandresources),andcomposingthedifferentstepsinsideastructuredenvironment,withouthavingtowritesubmissionscriptsorresourcedescriptionfiles.Thehigh-levelfeaturesofferedbyVEGAareintendedtoprovidetheuserwitheasyaccesstoGridfaciliti