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

Outline I. Pervasive Computing II. The Cognitive Hurdle III. Basic Proposition IV. What is a Service? V. Service-Based Paradigm VI. Mapping: SbP to Pervasive Computing VII. Enabling Technologies VIII. Case Study: Web Services IX. Why SbP? X. New Frontiers

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

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)

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.

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.

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.

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.

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, s i, s f ) ⇚ R] ⇒ PostCond.

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.

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

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 …

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…

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

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.

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.

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

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

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

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

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

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.

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.

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.

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.

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.

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.

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.

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.

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