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Service-Based Paradigm

Service-Based Paradigm. Anchoring the Indefinable Field Of Pervasive Computing. Presenter: Vijay Dheap. Outline. Pervasive Computing The Cognitive Hurdle Basic Proposition What is a Service? Service-Based Paradigm Mapping: SbP to Pervasive Computing Enabling Technologies

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Service-Based Paradigm

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  1. Service-Based Paradigm Anchoring the Indefinable Field Of Pervasive Computing Presenter: Vijay Dheap

  2. Outline • Pervasive Computing • The Cognitive Hurdle • Basic Proposition • What is a Service? • Service-Based Paradigm • Mapping: SbP to Pervasive Computing • Enabling Technologies • Case Study: Web Services • Why SbP? • New Frontiers

  3. Pervasive Computing “Environments saturated by computing and communication capability, yet gracefully integrated with human users” • Computing and Communication - Anywhere & Anytime • Smart Spaces, Self-tuning … • Transparent, Proactive, Intelligent … • Context Awareness / User Intent • Evolution rather than Revolution

  4. The Cognitive Hurdle Pervasive Computing as a whole is discussed with relation to its Vision. When attempting to crystallize that Vision, various aspects are considered in terms of technologies required. • A checklist of criteria that a pervasive computing environment should meet. • Technologies required for implementing a pervasive computing environment exists already, yet we must find the means of “gluing” them together. (Mobile Computing, Distributed Computing)

  5. The Cognitive Hurdle • Research lacks a roadmap for achieving the ideal vision of Pervasive Computing. • A grasp of the research focus in this field has been evasive. • A clear, concise description or abstraction of Pervasive Computing has so far not been presented.

  6. Basic Proposition • Resources are present in our environment. • Building a pervasive computing environment requires that the resources available in the environment be manipulated in a manner to assist computation anywhere at any time. • Access and utilization of resources can be termed as a service.

  7. Basic Proposition • Services are provided when demand justifies their creation. • The prevalence of diverse, yet useful services in a particular location would enable the establishment of “smart spaces”. • Increasing the number and size of smart spaces will enable end users to experience a pervasive computing environment.

  8. What is a Service? The means employed to achieve a certain task or goal. • A service would be required to expose its functionality through interfaces. • Functionality would be defined as the purpose for the establishment of a service.

  9. What is a Service? • Resources are consumed or employed upon execution. • The contract of the service is that given a set of pre-conditions, a certain set of post-conditions will result through the execution of the service. S ≡ PreCond ⇒I [F (IN, OUT, si, sf) ⇚R] ⇒PostCond.

  10. Service-Based Paradigm It encapsulates all the high-level characteristics and concepts associated with a pervasive computing environment. It delineates the core research segments necessary to construct a pervasive computing environment.

  11. Service-Based Paradigm Segments: • Service Description • Service Offering/Discovery • Service/Request Matching & Service Composition • Service Execution & Management

  12. Service Description • A mechanism for demonstrating the functionality of a Service. • Information about a service including the inputs needed, outputs produced, constraints that must hold on these inputs and outputs, the protocols used … • Access to both static and dynamic attributes of the service. Constraints/Interrelatedness: support for automation – service offering/discovery, access …

  13. Service Offering/Discovery Motivation: Transition away from manual configuration each time new devices or applications are incorporated into an environment. • Mechanism employed significantly dependent on computing/communication infrastructure. • Mechanics of this segment are well understood. Constraints/Interrelatedness: problem of interoperability – service to request matching, service composition…

  14. Service/Request Matching Gap between service availability and invocation. • Analyze services offered and provide suitable responses for requests. • QOS issues: response time of the matching procedure; selection among alternatives Constraints/Interrelatedness: Approach will depend on syntactic vs. semantic debate in service descriptions and standardization of mechanisms in service offering/discovery

  15. Service Composition • Many-to-one matching of services to requests. • Semantic interaction a necessity. • Drawing knowledge from Artificial Intelligence – predicate & situational calculus – required for planning. • Dynamic or static composition of services based on computing/communication infrastructure. • Partial satisfaction of requests. Constraints/Interrelatedness: Assigning the responsibility for composing services – service management.

  16. Service Execution & Management • Entails invoking the functionality of a service through defined interfaces that are publicly accessible. • Insight from distributed, network-centric computation. • Requires loosely-coupled systems. • Reliability, fault tolerance achieved through service execution management.

  17. Service Execution & Management • Delegation of administrative overhead. • Multi-level management Constraints/Interrelatedness: Complexity dependent on service composition (interaction among a number of services), service description (contracts)

  18. Mapping • Application: A coordinating set of services. • Context Awareness/User Intent: Service offering, service matching/composition. • Self-tuning & adaptability: Service description, service management.

  19. Mapping • Intelligent/Proactive behavior: Service composition, service management. • Transparency/Invisibility: Automating the cycle - service offering/discovery→ service/request matching & service composition→ service execution & management.

  20. Enabling Technologies • Computing Infrastructure: Embedded, Mobile, Fixed. • Networking Technologies: Mobile Wireless Communications. • Distributed Computing (P2P)

  21. Enabling Technologies • Service-Oriented Software Design • Power Management • Security: Trust, Privacy, Secure Systems. • Sensor networks

  22. Web Services Web services are one specific type of service that can be offered. At present it can be conceptualized as a limited deployment of a virtual pervasive computing environment. • Service Description: Web Services Description Language (WSDL). • Service Offering/Discovery: Universal Description, Discovery, and Integration (UDDI). • Service/Request Matching & Service Composition: UDDI. • Service Execution & Management: Web server and client.

  23. Web Service Description • XML is the standard meta language to describe the services offered. • WSDL is an XML based specification that provides for syntactic description of Web Services.

  24. Web Service Description • Darpa Agent Markup Language for Web Services (DAML-S) is also an XML based specification but is being promoted for semantic description of Web Services. • Semantic descriptions make use of ontologies which are shared vocabularies and can be used to reason about service functionality.

  25. UDDI • The mechanism used for offering and discovering web services – Directory Service. • Service providers register with the directory service. • Service users query the directory for services.

  26. UDDI • The directory service provides service users with necessary information (URL) about the requested services to invoke them. – syntactic matching. • Subsequently the service provider and the service user interact directly.

  27. Web Services Execution • The web server and the client are only entities involved once a web service is invoked. • Fault-tolerance is the responsibility of the client. • Satisfies the loosely-coupled requirement. • QOS management is managed by the web server. • Composition of web services is possible but has to be done explicitly or statically.

  28. Why SbP? • Clear, concise and extendable abstraction of Pervasive Computing. • Bottom-Up approach free of proprietary methodology. • Facilitates the recognition, integration and coordination among research projects. • Enables identification of points where standardization is required.

  29. New Frontiers Power to explain the growth of interest in Grid Computing and Autonomic Computing. • Computing power is the primary service of interest in grid computing. • A hierarchical structure of the management services is the basis of Autonomic Computing.

  30. Questions?? Comments… “If the facts don’t fit the theory, change the facts” – Albert Einstein “If you can’t convince them, confuse them” – Chinese Proverb

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