Semantic Web

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Semantic Web

• Dushyant Rajput (05005003)
• Neelmani Singh (05005019)
• Pratik Jawanpuria (05005022)
• Jayant Nagda (05D05001)
• Nirdesh Chauhan (05D05002)

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Motivation

• Problem Web was built for humans
• web content today is designed for humans to read,
  not for computer programs to read and manipulate.
• Computers have no reliable way to process the
  semantics and bring structure to the meaningful
  content on the web.
• Solution make the Web friendlier for machines
• we need machine-understandable content (not
  machine-readable, we already have that)
• machine-understandable means content with
  accessible formal semantics
• Why semantic web?
• Extend the current existing paradigm of human
  computer interaction which will allow machines to
  analysis data in a much better way which they
  merely display right now.

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• The Semantic Web is an evolving extension of the
  World Wide Web in which the semantics of
  information and services on the web is defined,
  making it possible for the web to understand and
  satisfy the requests of people and machines to
  use the web content.
• - Wikipedia

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Semantic Web Architecture
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Semantic Web Agents

• Nirdesh Chauhan

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World in the reign of Semantic Web
My agent interacts with IMDB server agent to find
some sci-fi movies with rating gt 8.0
Me I want to see a movie. Give me some
suggestions.
Me Can Dr. Bose postpone the appointment to
tomorrow morning??
Me Fine !! Schedule my appointment and also book
the tickets for 6 pm show.
Me No, give me some current sci-fi movies !!
Agent Matrix and Krrish are some good
options.Matrix is currently running in Huma
Adlabs. Shows at 6 pm, 930 pm.
Me Ok. Book my tickets for show at 6.
Agent Taare Zameen Par and Chak De India are
good options.
Agent You have an appointment with Dr. Bose at
630. Should I book ??
My agent interacts with Mr. Boses agent.
Agent Tomorrow morning 9 am is fine with Dr.
Bose.
My agent interacts with trusted agents to enquire
about some good movies
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Semantic Web Agents

• An agent is an intermediary who makes a complex
  organization externally accessible.For example,
  travel agent.
• Semantic Web AgentPrograms that collect Web
  content from diverse sources, process the
  information and exchange the results with other
  agents.
• Semantic Web may be viewed as1. An expert
  system with a distributed knowledge base.2. A
  society of agents that solve complex
  knowledge-based tasks.
• Agents are viewed as primary consumers of
  knowledge. Agents capture the notion of the use
  of entities to solve complex problems on the Web.

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Characteristics of Agents

• There is no such standard definition for an
  agent. However some peculiar characteristics that
  a Semantic Web Agent must possess are
• IntelligenceAutonomyReactivityPro-activenessS
  ocial ability
• These definitions are subject to different
  interpretations.For example, there are many
  different definitions of what it means for an
  agent to be truly autonomous.
• All that we require is that our agent can
  interact with other agents, and do useful work
  for us.

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Multi-Agent System

• MAS is a system composed of several software
  agents, collectively capable of reaching goals
  that are difficult to achieve by an individual
  agent
• MAS are necessarily distributed and concurrent in
  nature.However, A distributed system prescribes
  a static pattern of behavior towards a common
  goal.Whereas an agent system is more dynamic
  with individual agents acting autonomously
  towards their own goals.
• Agents in a MAS1. Work autonomously to achieve
  their own goal.2. Interoperate with other agents
  as a part of MAS.

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Reactive Agents

• A purely reactive agent does not perform any kind
  of deduction. Hence, relatively straightforward
  to implement and map environment states directly
  to actions. E.g. Stock price monitoring.
• They act as a sensor on the environment and are
  triggered by specific events.
• Engineered to respond to changes in the
  environment which we represent as input events.
  A(environment state) ? action
• Implementation
• Equation-based approach - for events that occur
  many times, such as price fluctuations.State-base
  d approach - for events that are largely
  one-time, such as messages.

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Practical Reasoning Agents

• The practical reasoning agents based on the BDI
  model.B(beliefs) - knowledge about the current
  environment state.D(desires) - state of affairs
  the agent would like to bring about.I(intentions)
  - desires that the agent has committed to
  achieving.
• Commitment strategies used to determine the
  persistence of the intentions Blind,
  Single-minded and Open-minded.

Reason(B, D, I) Do p ? next percept
// Changes in the behaviour triggered by external
events B ? revise(B, Ò) // Agents
beliefs are revised in light of these percepts
D ? options(B, I) // No. of possible
options arise for action I ? deliberate(B, D,
I) // Agent deliberates on competing options P
? plan(B, I, A) // performs a meansends
analysis on the intentions. execute(P)
// Once a suitable plan (P) has been formed, we
execute while true
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Semantic Web Logic Layer

• Neelmani Singh

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Semantic Web Logic Layer

• For the Semantic Web, semantic indicates that the
  meaning of data on the Web that can be
  discoverednot just by people, but also by
  computers
  
• But this discovery is not possible without logic.
  
  
• Computers will need to apply logical reasoning to
  all kinds of statements , and those statements
  will be distributed across the Web.

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• Roles of Logic for the SW
• Application and evaluation of rules
• Inferring facts that havent been explicitly
  stated.
• Explaining why a particular conclusion has been
  reached.
• Detecting contradictory statements and claims.
• Specifying ontologies and vocabularies of all
  kinds.
• Representing knowledge.
• Playing a key role in the statement and execution
  of queries to obtain information from stores of
  data on the Semantic Web.
• Combining information from distributed sources in
  a coherent way.

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Rules

• Specialized kind of rule used , the kind often
  used by so-called expert systems
  
  IF ltlogical conditions are metgt
  
  THEN ltperform specified actionsgt
  
• Evaluating the truth of the logical conditions
  involves logic, but there is more to it. Rules
  are often chained together.
• The Semantic Web will have several additional
  needs
• A Web-compatible language for expressing rules
• The ability to specify the kinds of rules and
  their relationships and constraints.
• Ways to handle incompatible rules.

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Inferring facts and Explanations

• The Semantic Web will be a very large, open
  system. So inferring facts from given facts and
  rules is essential (Open World model).
  
• The ability to explain a train of reasoning may
  emerge as one of the most important capabilities
  a Semantic Web reasoning system can have.
  
  
  
• If Pratik is allowed access to Neelmani's bank
  account, it may become important why the
  conclusion was reached.
• If Mr. Dushyant's mothers name is Sunita then
  Sunita must be a woman.

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Contradictions and Interpretations

• What will happen if a Semantic Web system
  encounters a contradiction?
• Isnt trivial because in pure logic, a
  contradiction would allow anything to be proved.
• The obvious thing to do would be to regard each
  statement as a kind of claim that may or may not
  be strongly supported.
• To provide an alternative, the current version of
  the RDF specifications define a way to understand
  the meaning of a collection of RDF statements
  that can deal with the possibility of
  contradictory information at the cost of more
  computing power.

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Combining information

• Problems can arise from trying to combine
  information from multiple sources on the Semantic
  Web. Here are some of the most prominent
  
  
• Different sources may use different ontologies
  (different vocabularies for the same things)?
• Different sources may have different semantics
  for the (apparently) same things.
• Different sources may contain contradictory
  information.
• Different sources may have different degrees of
  reliability.

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Ontologies

• An ontology establishes the things that a system
  can talk and reason about. This means the
  vocabulary.
• The terms have logical relationships to each
  other that need to be specified, and this in turn
  means that any ontology system must adopt some
  variety of logic.
• Ontology supplies the concepts and terms.
• logic provides ways to make statements that
  define and use them, and to reason about
  collections of statements that use the concepts
  and terms.
• In the Semantic Web, the role of logic will be
  very different from the role of most other
  components of the Semantic Web layer cake.
  
  
  
  But WHY ??
  
  
  
  Because it isnt information
  to be exchanged.

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Semantic Web Components

• Dushyant Rajput

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Semantic Web Components

• Extensible Markup Language(XML) provides an
  elemental syntax to structure data.
• XML schema provides and restricts the structure
  and content of elements in XML documents.
• Resource Description Framework (RDF) is a
  language for expressing data models in XML
  syntax.
• RDF schema is a vocabulary for describing
  properties and classes of RDF-based resources.
• Web Ontology Language (OWL) provides additional
  vocabulary for describing properties and
  relations between classes.

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• Resource Description Framework
• The need for RDF -
• Make all data and metadata accessible to
  computers and addressable over networks.
• Provide standard way to refer to any particular
  bit of information.
• To achieve these RDF uses a simple data model -
• Resources refers to objects.
• Statements links two resources. It encodes
  information as triples subject
  predicate/property - object/value.

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RDF (continued ...)?

• Example
• (Person, Name, Neelmani Singh)?
• Subject Predicate
  Object

• Resource Identification -
  URI
  (Uniform Resource Identifier) references
  URI fragment identifier(the part that follows
  the sign after a URI, if any).
  Eg- http//www.w3.org/1999/02/22-rdf-sy
  ntax-ns Statement

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RDF Graph representation
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Ontology Framework

• Resource Description Framework Schema
  Specification (RDFS) provides semantics for
  generalized-hierarchies of properties and
  classes.
• Web Ontology Language (OWL)
• Uses properties of RDFS along with new ones.
• Has W3C recommendations.

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Semantic Web Services

• Jayant Nagda

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Web Services

• Web services are a new breed of Web application.
  They are self-contained, selfdescribing, modular
  applications that can be published, located, and
  invoked across the Web. Web services perform
  functions, which can be anything from simple
  requests to complicated business processes.
• Once a Web service is deployed, other
  applications (and other Web services) can
  discover and invoke the deployed service.

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Architecture

• Web
• URIs specific addresses of web-elements
• HTML way of describing documents.
• HTTP a protocol that is used to retrieve
  information on web.
• Semantic Web
• UDDI provides a mechanism of finding web
  services.
• WSDL defines a service.
• SOAP a message layout specification that defines
  a uniform way of passing XML-encoded data.

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Describing a web service

• WSDL (Web Services Description Language) is an
  XML-based language that provides a model for
  describing public interface to a Web services.
• Services as a collection of ports. Messages are
  abstract.
• A client program connecting to a web service can
  read the WSDL to determine what functions are
  available on the server.

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Discovering web services

• UDDI (Universal Description Discovery and
  Integration)is a platform-independent, XML-based
  registry for businesses worldwide to list
  themselves on the Internet.
• UDDI is an open industry initiative, sponsored by
  OASIS, enabling businesses to publish service
  listings and discover each other.

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SOAP

• SOAP (Simple Object Access Protocol) is a
  protocol for exchanging XML-based messages over
  computer networks, normally using HTTP.
• SOAP uses RPC (Remote Procedure Call)

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Semantic Web Trust

• Pratik Jawanpuria

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Semantic Web Trust

• The concept of Semantic Web is great, but who
  would trust such as system if anyone can say
  anything
• If one person says that x is blue, and another
  says that x is not blue, doesn't the whole
  Semantic Web fall apart?
• So how to know which is trustworthy and whom to
  believe?
• To confront these situation, we have Semantic Web
  Trust.

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Trust Policies in Day to Day Life

• A trust policy is a subjective procedure used for
  evaluating the trustworthiness of information in
  a specific situation.
• Try Dominos's pizza good but not pasta.
• Trust Pratik on science fiction movies but not on
  political news.
• Believe in media only on sports news.
• See a movie if its IMDB's rating in above 7.
• Trust professors on their research field.
• We have to allow similar range of trust policies
  on the Semantic web

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• Digital Signature

• Web of Trust

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• Policy-based Trust Management
• Trust relies on "STRONG SECURITY" mechanisms such
  as digital signatures and trusted certification
  authorities.
• Seen as a solution of problem of authorization
  and access control in open systems.
• Reputation-Based Trust Management
• include rating systems like the one used by eBay
  and Web-Of-Trust mechanisms.
• IMDB's movie ratings
• Social networks like Orkut, Facebook.

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• Context-Based Trust Mechanisms
• Use meta information about the circumstances in
  which information has been claimed e.g. who said,
  what, when and why.
• Trust a toothpaste if a dental doctor prescribes
  it
• Include role based trust mechanisms, using the
  author's role or his membership in the specific
  group, for trust decisions.
• Distrust all members of organization X
• Content-Based Trust Mechanisms
• Use rules and axioms together with the
  information content itself and related
  information about the same topic given by other
  providers
• Distrust the cricket news if India makes less
  than 100 runs.
• Distrust product prices that are more than 50
  below the average price.

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Integrated View of Trust Management

• Each of the above mechanism address the problem
  from a different perspective.
• In many cases it will be desirable to combine
  them to handle situations like
• a seller is interested in protecting an item on
  sale in different ways depending on the value of
  the item based on reputation if the price is few
  hundreds of rupees (e.g. a T-shirt) or based on
  policies if it is of thousands (e.g. requiring a
  digital signature for flight ticket)

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Prototype of trust architecture

• retrieved information is used within the
• applications context
• - provides functionality to browse through
• explanations why data should be trusted

• handles the actual trust decisions
• using query-specific trust policies

- stores the aggregate information

• handles the aggregation of information
• from different sources
• add provenance metadata to the
• information
  

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Conclusion

• Ontologies ? Reasoning ? Agents ? Trust
• Knowledge representation is very well developed
  insemantic web.
• We need to
• move from tools to autonomous systems that work
  on our behalf
• introduce formal semantics (machine-understandable
  content)
• Semantic web trust and agent communication still
  remains the least explored of all the layers of
  semantic web.
• Search engines based on ontologies have already
  come uphttp//swoogle.umbc.edu/

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Bibliography

• Explorers-guide-to-the-semantic-web (by Thomas B.
  Passin)
• Agency and the Semantic web (by Christopher
  Walten)
• Using Context- and Content-Based Trust Policies
  on the Semantic Web. WWW2004 Christian Bizer,
  Radoslaw Oldakowski.
• An Integration of Reputation-Based and
  Policy-Based Trust Management The Semantic Web
  and Policy Workshop at ISWC2005
  (citeseer.ist.psu.edu/576212.html)
• http//www.scientificamerican.com/article.cfm?arti
  cleID00048144-10D2-1C70-84A9809EC588EF21catID2
  (by Tim Berners-Lee)
• Semantic Web Services (IEEE, 2001), Sheila A.
  McIlraith, Tran Cao Son, and Honglei Zeng,
  Stanford University.
• Wikipedia (http//www.wikipedia.com)
• http//logicerror.com/semanticWeb-long

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