Conceptual model of Web Service Reputation

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Conceptual model of Web Service Reputation
By E. Michael Maximillien and Munindar
P.Singh

• Soumya Bandalli
• Karen Doore
• Preeti Ganeshmohan

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Agenda

• Introduction
• Motivation
• Web Service Agent Proxy
• Conceptual Model
• Conclusion
• Future Work

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Introduction

• Current approaches of web services provide no
  basis for selecting a good service or comparing
  ratings of services.
• A conceptual model for reputation have been
  developed, using which reputation information can
  be organized and shared and service selection can
  be facilitated and automated.

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Motivation

• Limitations of Current approaches
• Lack dynamic discovery and binding processes
• No memory of Service bindings and Interactions
• share their knowledge.
• require ratings

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• Developer an architecture
• Uses software agents
• Service reputation and Endorsement are
  disseminated
• Key semantic questions?

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• Addresses the semantic questions by developing a
  conceptual model of a service providers
  reputation for delivering quality services.
• Addition of WSAP (Web Service Agent Proxy) to
  access each service.

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Architecture of WSAP

• Agent is a software component that automates some
  task
• Communicate
• Accepts requests
• Acts as a proxy
• WSAP for each service

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Challenges

• Can we define a generic conceptual model for
  attributes reusable across domains?
• The threshold of the values of the attributes
  that the user is willing to accept.
• The risk of tolerance of the user.

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Web Service Reputation Conceptual Model

• A Web service represents a set of functions
  addressing a particular domain.
• Web Service Attributes
• Generic Attributes
• Domain Specific Attributes
• Reputation of a web service
• Is a function of a web service that depends on
  attributes
• It depends on the relative importance of each
  attribute with respect to the agent using the
  service.

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WASP Web Service Agent Proxy
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Conceptual Model UML Static Model Figures
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• A Web Service has 1 associated Reputation for an
  agent considering the service
• A Reputation of a service is a vector of
  attribute values
• A Reputation is determined by a reputation
  algorithm that aggregates attributes that are
  selected to be considered by the agent.
• A Reputation is also affected by a History, that
  keeps previous ratings for a particular service
• The rating for a particular service is determined
  for a particular principal (agent) using the
  Rating Algorithm which takes into consideration
  the agents bias about the relative importance of
  each attribute.
• Endorsements by other Principals (agents) are
  also considered for determination of Reputation,
  the weighting given to an endorsement is
  dependant on the trust level of the Principal
  giving the endorsement.

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Attributes Model
Domain are collections of attributes for a
specific type of service Cross-Domain
attribute Domain specific attribute
Attributes Each Attribute has a range, or
set of allowed values can be integer,
percentage, Boolean, etc. Relative Weight of
an Attribute Relative to Domain User
preferences Characteristic function from
Attribute value to Rating S-shaped lower
threshold and upper saturation level Monotonicall
y Increasing Step-wise function Temporal
Characteristic Decaying value of an attribute
Example travel delay, if a plane is delayed 10
minutes is tolerable, however a delay of 45
minutes may be intolerable because it causes
problems with connecting flights.
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Generic and Domain Specific Attributes
Web Service Attribute Domains For Web services
that provide similar services, they will share
common attributes, perhaps weighted differently
For different domains. Example Car rental
service Domains Travel Price,
Flexibility of Reservation Changes Retail
Price, Inventory Flexibility of Reservation
Changes may be used by some services to
differentiate their service. Determining
Attributes for a Domain Suggestion let the
attributes for a domain be determined by
community of users and providers for each
domain. Ideally, want a system where new
attributes can be added to domains, and where
services can distinguish themselves by focusing
on certain attributes. So that service doesnt
need to have values for all attributes.
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Conceptual Model Web Services Agent Proxy
Client Desires Service Client uses WSAP to
access web services. Web Services Agent Proxy
Consults with outside registries, reputation
and endorsement agencies to find an appropriate
provider of a desired web service. WSAP can use
information about the users priorities with
information in the form of reputation attributes
and endorsements to determine the service which
is optimum for the client. The WSAP can provide
feedback to the reputation and endorsement
agencies based on the WSAP and user experience to
keep reputation and endorsement data up to
date.
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Web Service Reputation Important Factors

• Relative Weights given to attributes
• Dependant on Agent Biases, Dependant on Specific
  Domain
• Attribute Aggregation Algorithm
• Simple Majority, Other Algorithms
• Endorsers of the Service
• Trust level of Endorsers
• History of Service
• Services that are new wont have as many
  endorsers
• Older services have more history data
• Dampening Factors for Ratings
• Allows a web services reputation to increase
  with improved service
• More recent activity matters more than old
  activity

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Model of Web Service Reputation

• Travel Reservation Web Application
• Set up Business and Personal travel arrangement
• Select, Search and Reserve car rental as part of
  travel arrangement
• Attributes for Car Rental
• Price
• Comfort and Reliability
• Color

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Travel Reservation Web Application

• What does the application do?
• ?Set up business and personal travel arrangement
• Problem?
• ?Many car rental companies available. Each
  advertising its services on the web.
• Thus, an interface car rental Web Service is
  available.
• What does the agent do?
• ? Each car rental company would provide an
  implementation of its service. This allows the
  business to collaborate with other car rental
  companies.

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Travel Reservation Web Application

• How is the WSAP proxying the car rental service
  to pick the best service for a particular client?
• ? WSAP picks the correct service implementation
  by looking at the reputation of the various
  services.
• What is Reputation?
• ? Function of historical ratings provided by
  previous users filtered to take into account the
  attribute values that WSAPs principal needs.
• What does this mean?
• ? If user attribute Price is important cross
  domain attribute then services giving lower price
  might be selected over those giving higher
  prices.
• Multiple attributes would also be given more
  weight.

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Travel Reservation Web Application

• Example where multiple attributes are given
  importance
• Car rental Web service overlaps with Car selling
  Web Service
• Attribute of Car rental Web service
• Price
• Comfort and Reliability
• Attribute of Car selling Web service
• Color
• Comfort and Reliability
• Now color has more significance for a buyer than
  a renter.

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Travel Reservation Web Application
How does WSAP help? ?WSAP configures with all
attributes that apply to the domain that the
service belongs. Thus it takes all the subtleties
into account. ? To decide the domain, it should
satisfy all the pre conditions of the domain
before agent configuration. ? WSAP is generic
and allows the introduction of new attributes.
? So in our car rental example, if we add new
attribute Safety, then any new agent that was
configured with this attribute could take the
attribute into account for its rating
calculation. This can be obtained from user
surveys or collecting information on accidents
from the car types that the car rental company
rented for certain periods and the relative
safety outcome of the rentals. Outcomes of the
method ? Streamlining the attributes so that it
is standardized. ? New attributes added on the
fly ? New agencies can upgrade to the new
attributes ? Add attributes that it had
previously ignored
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Summary
WSAP enables applications to connect to any
suitable and accessible service
provider. Challenge ?Locate the service
providers. What is out there already? ?Semantic
Web such as OWL , RDF add ontology to the WWW
and Web Services. What is new? ?WSAP
discovers the service attributes dynamically
without forcing all clients to know the set of
attributes ahead of time. ?WSAP criteria of
selection reflect the reputation of the given
services wrt different attributes.
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Thank You !!!