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Trust Networks on the Semantic Web
A Knowledge Management Technologies Presentation
Chung, Hyung-Hwan (HT052383L)Ching Meng Hui (HT042310U)
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Trust
Top layer of semantic webUltimate goal: “Web of Trust”Human notion of trust
Complex and complicatedAbstractEmotional and illogicalBased on intuition.
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Types of Trust
Cognition-basedCalculative and rationalCompetence, ability, responsibility, integrity,
credibility, reliability and dependability.Affect-based
Non-calculative and emotionalCare, concern, benevolence, altruism,
commitment, mutual respect, etc.
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Trust in general
Based on expectations and interactions.Manifested in people’s behavioral
patterns.Makes a difference.
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Trust in Social Networks
Long research historyMathematical model
Small Worlds “Six Degrees of Separation”Game: “Kevin Bacon Game”
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Distorted Trust
MWW – Myanmar Wide WebExtreme censorshipLimited accessGovernment enforced
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Trust on the Semantic Web
AuthenticationDigital SignaturesPublic Keys
But trust is a human notion that ignores the above …
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Digital Signature
Verifies authenticity or identificationEnsures integrityPrevents repudiation
ProblemsExchange of certificatesEndorsements => CA
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Digital Signature
Public key and private keyEncrypt the plain text with a public keyDecrypt the encrypted text with a private
keyVice Versa.
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Digital Signature (cont’d)
Message Digest and HashContents provider
Get the digest of the plain textSign the digest with a private keyPublic the digest and the plain text together
Contents consumerCalculate the digest of the plain textDecrypt the signature with the public keyCompare the decrypted digest with the
calculated digest
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Friend-Of-A-Friend (FOAF)
Project using RDF Social networks Small world problem www.foaf-project.org
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FOAF File
<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#" xmlns:foaf="http://xmlns.com/foaf/0.1/" xmlns:admin="http://webns.net/mvcb/"><foaf:PersonalProfileDocument rdf:about=""> <foaf:maker rdf:resource="#me"/> <foaf:primaryTopic rdf:resource="#me"/> <admin:generatorAgent rdf:resource="http://www.ldodds.com/foaf/foaf-a-matic"/> <admin:errorReportsTo rdf:resource="mailto:[email protected]"/></foaf:PersonalProfileDocument><foaf:Person rdf:ID="me"><foaf:name>Hyung-Hwan Chung</foaf:name><foaf:givenname>Hyung-Hwan</foaf:givenname><foaf:family_name>Chung</foaf:family_name><foaf:nick>Brian</foaf:nick><foaf:mbox_sha1sum>de4f7c74a2050ab2c481daef8354ddf22fb049e0</foaf:mbox_sha1sum><foaf:knows><foaf:Person><foaf:name>Joe</foaf:name><foaf:mbox_sha1sum>5c38d396c3faf7424e291ccd7a29ce903e966332</foaf:mbox_sha1sum><rdfs:seeAlso rdf:resource="www.korone.net/foaf.rdf"/></foaf:Person></foaf:knows></foaf:Person></rdf:RDF>
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FOAF Level of Trust
1. Distrusts absolutely2. Distrusts highly3. Distrusts moderately4. Distrusts slightly5. Trusts neutrally6. Trusts slightly7. Trusts moderately8. Trusts highly9. Trusts absolutely.
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Extending FOAF
Quantify the trust Extra vocabulary
<foaf:person rdf:id=‘me’>
<trust>
<trustPerson rdf:resource=‘#dan’/>
<trustLevel>9</trustLevel>
<trustContext rdf:resource=http://example.com/ont#Java>
</trust>
</foaf:person>
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X trusts Y 80%
What does this mean?Are 8 statements out of 10 trustworthy?All of his statements might have 20%
discrepancy from the mathematically provable fact?
Depending on its definition, different metric should be devised to infer the trust value.
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Example
A
B C
D F
1
0.8 0.8
0.1
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Method 1
FCA: (0.1+0.8)/2=0.45DBA: (1+0.8)/2=0.9
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Method 2
FCA: (0.1×0.8)=0.08DBA: (1×0.8)=0.8
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Method 3
FCA: (0.8+0.8)/2=0.8DBA: (0.8+0.8)/2=0.8
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Applications
TrustBotTrustMail
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Conclusions
Trust has a role in KM.Trust values affect people’s willingness
to share and work.More empirical research on trust in the
context of knowledge-based world, to make this closer to reality.
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Questions & Answers
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Truweb.java
import java.util.*;
public class Truweb{ class Person { public String name; public Rating ratings = null; public Person next = null; public boolean visited = false; public Person (String name) { this.name = name; } }
class Rating { public int value; public Person target; public Rating next; public Rating (Person to, int value) { this.value = value; this.target = to; this.next = null; } }
private HashMap map;
public Truweb () { map = new HashMap (100); }
public Person addPerson (String name) { Person person; person = (Person) map.get (name); if (person == null) { person = new Person (name); map.put (name, person); }
return person; }
public Person findPerson (String name) { return (Person) map.get (name); }
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Truweb.java (cont’d)
public void setRating (Person from, Person to, int value) { Rating rating = from.ratings; while (rating != null) { if (rating.target == to) break; rating = rating.next; }
if (rating != null) { rating.value = value; } else { rating = new Rating (to, value); rating.next = from.ratings; from.ratings = rating; } }
public int getRating (Person from, Person to) { return get_rating0 (from, to, 0, 1); }
private int get_rating0 (Person from, Person to, int acc, int depth) { int n; from.visited = true; n = get_rating (from, to, acc, depth); from.visited = false; return n; }
private int get_rating (Person from, Person to, int acc, int depth) { Rating rating = from.ratings; if (rating == null) return -1;
do { if (rating.target == to) { return (acc + rating.value) / depth; } rating = rating.next; } while (rating != null);
rating = from.ratings; while (rating != null) { if (rating.target.visited != true) { int n = get_rating0 ( rating.target, to, acc + rating.value, depth+1); if (n != -1) return n; }
rating = rating.next; }
return -1; }
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Truweb.java (cont’d)
public static void main (String[] args) { Truweb truweb = new Truweb ();
Person jane = truweb.addPerson ("jane"); Person tom = truweb.addPerson ("tom"); Person jeff = truweb.addPerson ("jeff"); Person susie = truweb.addPerson ("susie"); Person kelly = truweb.addPerson ("kelly");
truweb.setRating (jane, tom, 1); truweb.setRating (jeff, tom, 10); truweb.setRating (susie, kelly, 7); //truweb.setRating (susie, jane, 7); truweb.setRating (tom, susie, 10);
System.out.print ("jane to kelly: "); System.out.println (truweb.getRating (jane, kelly)); System.out.print ("jeff to kelly: "); System.out.println (truweb.getRating (jeff, kelly)); System.out.print ("kelly to jeff: "); System.out.println (truweb.getRating (kelly, jeff)); System.out.print ("jane to tom: "); System.out.println (truweb.getRating (jane, tom)); }}