Dynamic Adaptation of Service Compositions Using Service Offerings

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Dynamic Adaptation of Service Compositions Using
Service Offerings

• Presenter Vladimir Tosic
• (work with K. Patel, B. Pagurek, B. Esfandiari)
• Network Management Artificial Intelligence Lab
  Department of Systems Computer Engineering
• Carleton University, Ottawa, Canada

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Outline

• Introduction to service-based software systems
• Overview of goals, definition of terminology, and
  an example
• Our research
• Research goals and our approach
• Service offerings and WSOL
• Dynamic adaptation capabilities
• The example revisited
• Current status and future work
• The DAMSC infrastructure
• Conclusions questions and answers

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Service-Based Software Systems

• Software is a service business model
• Applications decomposed into distributed
  components - services
• Different terminology service components, Web
  Services, e-services, dynamic services,
  eUtilities,
• Web Services industrial initiatives from
  Microsoft, IBM, HP, Sun, Oracle,
• Standards by W3C (World Wide Web Consortium)

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Some Goals of the Work on Web Services

• Faster development of complex software systems
• Flexible, adaptable, and agile business
  relationships
• Ad hoc A2A (Application-to-Application) and B2B
  (Business-to-Business) integration
• Interoperability of heterogeneous Web Services
• Leveraging existing Internet/Web infrastructure
  based on XML (Extensible Markup Language)
• Scalability to the Web
• gt Application area e- and m-business systems

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Definition of aService Component

• A unit of service provisioning and management
• Encapsulates some service functionality and
  appropriate data
• Software-based and/or hardware-based
• Composable, reusable, and replaceable
• Main use - service compositions
• Supplier and consumer
• A special case Web Service

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Example

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

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Our Research Goals

• Service compositions have to be managed
• Dynamic and autonomous adaptation is one
  management activity
• Approaches based on finding alternative service
  components are not always appropriate
• We work on additional and complementary support
• within service components
• to dynamically and autonomously adapt the
  composed service components and their
  relationships, without breaking these
  relationships

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Our Approach

• Dynamic adaptation using manipulation of classes
  of service
• Introduce the concept of classes of service for
  service components (extrapolate the corresponding
  concepts from telecommunications)
• Develop appropriate adaptation capabilities
  algorithms
• Implementation-independent solutions and their
  mapping to Web Services
• Appropriate infrastructure and its prototypes

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Multiple Classes of Service

• Variations of service and QoS (Quality of
  Service)
• Same functionality, but differ in constraints
• functional constraints
• non-functional (QoS) constraints
• authorization policies
• cost
• Increase chances to succeed in the market by
  broadening the market segment
• Enable balancing limited underlying resources, as
  well as the price/performance ratio

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A Service Offering

• A formal specification of a class of service
• Allowed combinations of interface-level service
  offerings determine component-level service
  offerings
• Specified separately from the specification of
  functionality
• Constraint dimensions are separated for easier
  specification, but integrated into service
  offerings for easier choice by consumers
• Specification of relationships between service
  offerings is a very important issue

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Service Offerings vs. Potential Alternatives

• Various potential alternatives
• Service offerings are an additional
  complementary mechanism for differentiation of
  service and QoS
• Not a complete replacement for alternatives
• Advantages of service offerings include
• additional flexibility
• relatively low overhead
• limited complexity of required management
• support for dynamic adaptation mechanisms

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WSOL - Web Service Offerings Language

• Explicit and formal specification of various
  constraints and service offerings for Web
  Services in XML
• supports dynamic selection of Web Services
• minimizes unexpected feature interactions
• 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)
• Reusing and extending existing Web Services tools

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WSOL - Current Status Future Work

• WSOL prototype parser
• Current issue functional constraints that
  include complex expressions
• Future work other constraints, particularly
  different dimensions of QoS
• Separation and integration of constraint
  dimensions is the main open issue
• Relationships between service offerings will be
  specified using a combination of constraint
  dimensions and roles

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Motivation for Dynamic Adaptation Capabilities

• Goal accommodate changes without breaking
  relationships between service components
• Based on dynamic manipulation of service
  offerings
• Cannot completely replace finding alternative
  service components, but a useful complement
• Advantages include
• adaptation speed
• enhanced robustness of relationships between
  service components
• simplicity and relatively low overhead

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ThreeDynamic Adaptation Capabilities

• Switching between service offerings
• Initiated by the service component or its
  consumers
• Deactivation/reactivation of service offerings
• With automatic accommodation of affected
  consumers
• Creation of new appropriate service offerings
• Not creation of new functionality
• The service component decides when it is possible
  and allowed

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The M-Commerce System Example Revisited

• Benefits of service offerings and the suggested
  dynamic adaptation mechanisms

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DAMSC Infrastructure

• DAMSC - Dynamically Adaptable and Manageable
  Service Compositions
• Goal to support
• service offerings
• the suggested dynamic adaptation capabilities
• sessions (supplier-consumer associations that
  remember state of the interaction handle
  persistent interactions)
• Infrastructure inside service components
• Complements works that suggest management
  infrastructure outside service components
• A proof-of-concept prototype - for Web Services

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DAMSC - Current Status Future Work (Part I of
II)

• Standardized management operations/interfaces
• Investigating use/extension of the Common
  Information Model (CIM)
• Support for service offerings includes
• storage of service offerings inside service
  components
• informing consumer about active and available
  service offerings
• storage of relationships with other service
  components
• Support for dynamic adaptation includes
• storage of relationships between service
  offerings
• storage of rules for creation of new service
  offerings

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DAMSC - Current Status Future Work (Part II of
II)

• Dynamic adaptation will be supported in sessions
• It should not destroy the session state
• Support for sessions
• Standardization of session-management operations
• A session element stores information about a
  session at the supplier side
• It should also contain the constraint-checking
  code
• Automatic generation of session elements (except
  code!)
• A number of open issues remain
• Relating DAMSC to other approaches for managing
  service components and service compositions

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Some Related Work

• Web Service industrial initiatives and standards
  management approaches in these initiatives
• Adaptation by finding alternative service
  components
• Network/system/application/service management
• Differentiated services and classes of service in
  telecommunications and TINA (Telecommunications
  Information Networking Architecture
• Formal specification of constraints for software

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Conclusions (Part I of II)

• This research is about improving flexibility,
  adaptability, and agility of service compositions
• The suggested capabilities complement prior works
• More appropriate than alternatives in some
  circumstances
• Main advantages
• adaptation speed
• enhanced robustness of relationships between
  service components
• simplicity and relatively low overhead
• limited complexity of required management
• However, our approach has limitations

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Conclusions (Part II of II)

• The research has theoretical and practical
  relevance
• The overall problem has not been previously
  addressed
• Practical relevance - e.g., for compositions of
  e- and m-business Web Services
• Critical analyses are conducted at all research
  stages
• To determine benefits and limitations
• Proof-of-concept prototypes for Web Services
• To check feasibility, uncover hidden issues, and
  demonstrate contributions
• WSOL - there are already some results
• DAMSC - in the beginning stages of development

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Questions and Answers,For More Information

• For more information
• WWW site http//www.sce.carleton.ca/netmanage/
• Contact e-mail vladimir_at_sce.carleton.ca