Adaptive Middleware for Real-Time SoftwareTopicUbiquitous ComputingMobile Ad Hoc Networks (MANET)Their GoalContext-Sensitive ServicesMiddleware: DefinitionCORBACORBA ExampleSlide 10Interface Definition LanguageSlide 12CORBA ArchitectureMiddleware BenefitsMiddleware: LimitationsChallengesSlide 17Reconfigurable Context-Sensitive Middleware (RCSM)RCSM FeaturesRCSM Component HierarchyDevelopment and Runtime SupportContext-sensitive Application ObjectSpecifying a ContextDevice-specific ContextEnvironment-specific ContextUser-specific ContextContext VariablesTemporal OperatorsContext ExpressionsContext-Sensitive Interface SpecificationIncoming and Outgoing TagsInterface ExampleInterfaceExampleExample: Sensor NetworkSlide 35Object MB: Mobile Robot ObjectObject M: Motion Data CollectorObject N: Noise Data CollectorAdaptive Object ContainersSlide 40ADC ArchitectureGenerated ADCContext PropagationContext Match EventObject Discovery MessagesObject Match EventsInter-Object CommunicationMotion Detector Sends DataObject MB Receives Motion DataR-ORB ImplementationFuture DirectionsSlide 52Adaptive Middleware for Real-Time SoftwareLouise AvilaCIS 700-02November 2, 2005Topic“An Adaptive Middleware for Context-Sensitive Communications for Real-Time Applications in Ubiquitous Computing Environments.” Real-Time Systems Journal. January 2004. Stephen S. Yau and Fariaz KarimReconfigurable Context-Sensitive Middleware Research Project, Arizona State UniversityUbiquitous ComputingComputing experience is everywhere but enabling technologies are invisible Makes the user the center of computingDynamically adapt to user’s needs and actionsMobile Ad Hoc Networks (MANET)Collection of connected autonomous mobile nodes such as wearable, handheld and other mobile devicesFree to move arbitrarilyBandwidth and energy constraintsDynamic network topologiesNo dedicated network connectivity devicesNodes form short-range wireless networksTheir GoalMake MANET context-sensitiveUse data about environment and available resourcesAdapt behavior and interactionsSchedule and execute time critical tasksContext sensitive interactions between applicationsContext-Sensitive ServicesDetects, establishes and terminates communication channels New devices enter the environment Existing devices move awayEfficient Address heterogeneity of devicesOne potential solution: middlewareMiddleware: DefinitionSoftware is distributed and developed using different languages, operating systems and hardware platformsMiddleware "glues together" or mediates between two separate programs or software packagesCORBACommon Object Request Broker ArchitectureCreating and managing distributed objects in a networkIndustry standard developed by the Object Management Group http://www.omg.org/CORBA ExampleHR Rep works in San FranciscoHR Application runs on a server in DenverEmployeeApplicationCORBA ExampleClient programs don’t need to know:Location of server programImplementation of serverPlatform IndependentLanguage IndependentInterface Definition LanguageEmployee server class:public class Employee {public String getEmployeeId(String name) { return eid; } }Define interface for Employee class:interface IEmployee {String getEmployeeId(in String name); }CORBA ExampleCompile interface with IDL compilerClient StubProxy for the server that runs on the clientConverts method calls into messagesClient acts as though invoking on local object instanceServer SkeletonConverts messages back to method callsCORBA ArchitectureObject Request Broker (ORB)Locates and activates objectDelivers requestReturns responseOther servicesNaming, Lifecycle, etc.Middleware BenefitsReduce effort required to develop software Provide runtime services for applicationsForces a separation between interface and implementationORB approachIsolate transport protocols from applicationsMiddleware: LimitationsExisting middleware for enterprise and mobile networks:Industry standards: CORBA, COM, EJBSpecialized “laboratory” versions: TAOAssume stable networkUse client-server interaction semanticsDo not use different contextsLaboratory versions have unique architectures – problem of interoperabilityChallengesSystematic way to represent specific contexts and context awarenessTimely context data collection, analysis and propagationTransparentDevice and application-specificChallengesAssociating context with real-time actionsSupport for spontaneous and ad hoc context-sensitive communicationReconfigurable Context-Sensitive Middleware (RCSM)Compliant with CORBA/OMA User-level application software as application objects Object Request Broker (R-ORB)Enables application objects implemented in different languages to communicate in a distributed, heterogeneous environmentProvides context-sensitive communicationR-CAP performs low-level context monitoring and acquisitionRCSM FeaturesContext-aware interface definition language (CA-IDL)Based on IDLSeparates interfaces from implementationsAdaptive Object Containers (ADC) Interface-specific context analyzer components. Communicate at runtime with other components to acquire context dataCommunicates with the object implementation to invoke different methods when suitable contexts are detected.Client-serverobjectsRCSM Component HierarchyContext-sensitiveobjectsOperating SystemRCSM Groupcommunication serviceOtherservicesAdaptive object containers(ADCs)R-CAPR-ORBTransport layer protocols for ad hoc networksSensors(optional)Development and Runtime SupportDevelopment Support Runtime ServicesDeveloper specifies context-sensitive interface CA-IDL compiler generates interface-specific ADCCA-IDL compiler generatesobject skeletonDeveloper implements real-timeobjectDeveloper registers object with ORBContext analyzers and R-CAP monitor and analyze contextORB performs object discoveryORB establishes context-triggeredcommunication establishmentADCs perform context-basedobject activationContext-sensitive Application ObjectContext expression+Method signatureContext-independent implementation(C++, C, C# or Java)Context-sensitive interface (CA-IDL)Specifying a ContextTypes of context data available depend on host device and its context-sensing capabilitiesSteps to port RCSM to a new deviceClassify the context into categoriesDefine a