E-Business Service Components with Multiple Classes of Service and Dynamic Adaptability Mechanisms

1
E-Business Service Components with Multiple
Classes of Service and Dynamic Adaptability
Mechanisms

• Vladimir Tosic, Kruti Patel, Bernard Pagurek
• Network Management Artificial Intelligence Lab
  Department of Systems Computer Engineering
• Carleton University, Ottawa, Canada
• vladimir_at_sce.carleton.ca
• http//www.sce.carleton.ca/netmanage/

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Outline

• Research goals
• Definition of service components
• Service offerings - multiple classes of service
  for service components
• WSOL - Web Service Offerings Language
• Dynamic adaptation mechanisms
• Example - an m-commerce system
• DAMSC (Dynamically Adaptable and Manageable
  Service Compositions) infrastructure
• Conclusions and future work

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Research Goals

• Develop additional support within service
  components (e.g., Web Services) for adaptation of
  a service composition by dynamically adapting the
  constituent service components and their
  relationships, without breaking these
  relationships
• Complement mechanisms for dynamic composition of
  service components and adaptation by rebinding of
  service components
• Application area e- and m-business systems
• trust and customer retention are important issues
• additional agility, flexibility, and adaptability
  needed

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Definition of aService Component

• A composable, reusable, and replaceable
  self-contained unit of service provisioning and
  management that encapsulates some service
  functionality and appropriate data
• Main usage is composition with other service
  components into different services (but also can
  be used in isolation from other service
  components)
• Can be software-based (a.k.a., algorithmic)
  and/or hardware-based (e.g., memory, printing,
  network bandwidth, etc.)
• Special case e- and m-business Web Services

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Multiple Classes of Service

• Represent variations of service and QoS (Quality
  of Service) - differentiate provided services and
  QoS
• Relate to the same functionality, but differ in
  constraints and cost
• Increase chances to succeed in the market by
  broadening the market segment
• Allow a wider range of possible consumers, with
  different capabilities, rights and needs
• Allow usage in different circumstances
• Enable balancing of limited underlying resources
  and the price/performance ratio, and thus help to
  maximize the monetary gain

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Types of Constraints in Classes of Service

• Functional preconditions, postconditions,
  invariants
• Nonfunctional (a.k.a., QoS) QoS guaranteed to
  consumers and QoS required from suppliers
• Examples service priorities, guaranteed response
  times, verbosity of response information,
  required security, etc.
• Authorization policies (i.e., usage privileges)
• Dependencies from other service components and
  infrastructure
• Cost
• Other relevant information related components,
  alternative components, potential
  incompatibilities, synchronization and sequencing
  constraints, etc.

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A Service Offering

• A formal specification of a class of service for
  a service component or an interface
• Specified separately from the specification of
  functionality
• Contains specification of various types of
  constraints
• Different types of constraints are separated into
  distinct layers to achieve greater flexibility
  and reusability
• Allowed combinations of interface-level service
  offerings determine component-level service
  offerings
• Formal specification supports precise selection
  of service components and minimizes unexpected
  feature interactions in service compositions

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Service Offerings vs. Potential Alternatives

• Some potential alternatives
• separation of service and QoS dimensions,
  parameterization, multiple service components,
  multiple interfaces, service personalization
  techniques (e.g., user profiles)
• Service offerings are an additional mechanism for
  differentiation of service and QoS
• Although they are not a complete replacement for
  the above alternatives, service offerings have
  advantages like additional flexibility,
  relatively low overhead, limited complexity of
  required management, support for dynamic
  adaptation mechanisms, etc.
• Can be eventually combined with alternative
  mechanisms

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WSOL - Web Service Offerings Language

• Formal specification of service offerings for Web
  Services in XML (Extensible Markup Language)
• Extends WSDL (Web Services Description Language)
• We are working on prototypes for
• a WSOL parser (with syntax and some semantic
  checks)
• automatic generation of WSOL files using Java
• Java code generation from WSOL and WSDL
  specifications
• We reuse and extend existing tools IBM WSTK
  Toolkit v2.4 and Apache Xerces XML parser
• If necessary, we will also develop additional
  tools
• Still work in progress

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Motivation for Dynamic Adaptation Mechanisms

• Goal to accommodate changes that cannot be
  accommodated on lower system levels, without
  breaking relationships between service components
• Robustness of relationships is important in e-
  and m-business due to the issues of trust and
  customer retention
• Based on dynamic (i.e., run-time) manipulation of
  service offerings
• The service component has control and can
  restrict usage
• Relatively limited power, but advantages are
  speed, simplicity, and low overhead
• Provide additional agility, flexibility, and
  adaptability

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ThreeDynamic Adaptation Mechanisms

• Switching between service offerings
• Initiated by the service component or its
  consumers
• Deactivation/reactivation of service offerings
• Consumers using the deactivated service offering
  are automatically switched to an appropriate
  replacement
• After the reactivation, these consumers are
  automatically switched back
• Creation of new appropriate service offerings
• Not creation of new functionality, but creation
  of new sets of constraints for the existing
  functionality
• Useful after dynamic upgrades, changes in
  related service components, a request by a
  premium consumer

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Example - Part I (out of II)

• An m-commerce system built from third-party
  pay-per-use service components

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Example - Part II (out of II)

• Service offerings accommodate the variety of
  users, user devices, communication mechanisms,
  security mechanisms,
• Dynamic switching of service offerings
  accommodates temporary disturbances in QoS
  changes of user devices changes in trust,
  security, and rights etc.
• Dynamic deactivation/reactivation of service
  offerings when QoS cannot be supported in new
  circumstances
• Dynamic creation of new service offerings to
  accommodate new security mechanisms, user
  devices, classes of consumer with special deals,
  etc.

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DAMSC Infrastructure

• DAMSC (Dynamically Adaptable and Manageable
  Service Compositions) is an infrastructure
  supporting adaptation and management of service
  compositions with manipulation of service
  offerings
• We are working on a number of open issues, like
• How to relate service offerings for easier
  specification and easier automatic switching
• How to reduce the overhead of dynamic adaptation
• Where and how constraints are checked (e.g., QoS
  is measured) and enforced
• The concept of session objects
• Still work in progress

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Some Related Work

• Industrial Web Service initiatives (e.g.,
  Microsoft .NET and Sun ONE - Open Net
  Environment)
• We add multiple classes of service and dynamic
  adaptation
• Differentiated services and classes of service in
  telecommunications and TINA (Telecommunications
  Information Networking Architecture)
• We extrapolate and modify existing telecom
  concepts for computing service components (e.g.,
  Web Services)
• We add new dynamic adaptation mechanisms
• Reconfiguration by rebinding of service
  components
• We complement this adaptation mechanism for
  situations where it is not appropriate or incurs
  too big overhead

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Conclusions and Future Work

• Advantages of service offerings include
  additional flexibility, relatively low overhead,
  limited complexity of required management, and
  support for dynamic adaptation mechanisms
• Advantages of suggested dynamic adaptation
  mechanisms include speed, simplicity, low
  overhead, and enhanced robustness of
  relationships between service components
• WSOL - a prototype parser is under development
• DAMSC - there are still a number of open issues
  a prototype implementation will extend existing
  Web service technologies and use WSOL