System Software for Ubiquitous Computing Pervasive Computing 2002 Tim Kindberg, Armando Fox 2003 년 11 월 26 일 박준호

Contents Characteristics of Ubiquitous Systems Progress Report

Characteristics of Ubiquitous Systems (1/2) Two main characteristics of ubicomp systems –Physical integration –Spontaneous interoperation Physical integration –MediaCup, Classroom2000, ICrafter –Should divide the ubicomp world into environments with boundaries that demarcate their content –A boundary should specify an environment ’ s scope but doesn ’ t necessarily constrain interoperation

Characteristics of Ubiquitous Systems (2/2) Spontaneous interoperation –Participating users, hardware, and software is highly dynamic and unpredictable –Clear invariants that govern the entire system ’ s execution should exist The semantic Rubicon –What system software will not do, but humans will –Division between system and user for high-level decision-making or physical world semantics processing

Progress Report Discovery Adaptation Integration Programming framework Robustness Security

Discovery and Interaction Ubicomp systems should be incrementally extensible To satisfy the spontaneous interoperation –Bootstrapping: a priori knowledge of address –Service discovery: dynamically allocate a service instance that matches a component ’ s requirements –Interaction: common interoperation model

Service Discovery Service discovery –Each provides syntax and vocabulary for specifying services –Attribute-value: serviceType=printer, type=laser –Abstraction can lead to ambiguity  System designers must decide the human ’ s role to resolve tension between interoperability and ambiguity Boundary principle

Interaction (1/2) After associating to a service, a component employs a programming interface to use it Jini –Let service access code and data migrate to a device  However, how can the software in the device use the downloaded object without a priori knowledge of its methods

Interaction (2/2) Event system & tuple spaces –The system interface comprise a few fixed operations –The interactions are data-oriented  Don ’ t need direct knowledge of one another  However, these data-oriented systems have shifted the burden of making interaction consistent onto data items(events, tuples) Data-oriented interaction –Spontaneous interaction  Require ubiquitous data standardization for it to work across environment boundaries

Adaptation (1/2) Ubicomp –Limited and dynamically varying computational resource, Smart dust –The available resources tend to vary dynamically –Adaptation must often take place without human intervention, Calm computing  Transformation and adaptation for content and the human interface Content –Mobile computing research successfully addressed content adaptation for resource-poor devices at both the OS and application levels. –1-to-n, n-to-n –Coda file system, Odyssey, Smart clipboard, Pebbles project

Adaptation (2/2) The human interface –On-the-fly transformation of UI –Client intelligence VNC: display the bits and collect user input without knowledge of UI widget semantics X Windows, Tcl/Tk and JavaScript-enhanced web pages: manipulate declarative description of the interface elements and have the intelligence to render them itself Tcl/Tk framework: controllable entities export Tcl-code description, support level of indirection of specialized per-device or per-service interface generator Fully generalized mobile code facility such as Jini

Integration with the Physical World Need low-level application programming interfaces Phidget Context Toolkit framework –Expose a uniform abstraction of location tracking, hiding the details of the sensing system or systems used to collect the information Location awareness - Active Badge, Sentient Computing, EasyLiving, Intelligent Room

Programming Frameworks Programming frameworks –“ Hello World ” –Operating system or middleware, and the development language –Support for legacy applications and commodity OSs Middleware and framework –Services provided by a layer in between the operating system and the applications –Integrated facilities of sensor fusion, quality-of-service-aware resource management, code distribution, adaptive and distributed rendering, and security Interactive Workspace: tuple space Intelligent Room: Metaglue ActiveSpace: Gaia

Robustness and Routine Failures Failure is common case Expiration-based schemes and soft sate –Periodic advertisement announcing its presence or availability to the directory service Separating failure-free and failure-prone operations Group communication for free indirection

Security Trust –Human can make judgments about their environments ’ trustworthiness: exchange cryptographic keys –Physical world offers mechanism for bootstrapping security: short-range infrared Security for resource-poor devices –Physical integration impacts security protocols Access control –Authenticating users ’ identities –Time-limited capability Location New patterns of resource-sharing

Conclusion We are not aware of a de facto solution Insufficient part in Room-bridge system –Discovery, bootstrapping –Ubiquitous data standardization –Interaction model between devices –Content data and user interface adaptation –Security