Trust in Recommender Systems and Social Networks

Paolo MassaSoNet @ FBK, Trento, Italyhttp://sonet.fbk.eu

Invited talk at Future Networked Technologies / FIT-IT research calls openingGraz, Austria - June 9th, 2010

Slides licenced under CreativeCommons Attribution-ShareAlike (see last slide for more info)

What I talk about

My personal visions and suggestions for collaborative research projects funded by FIT-IT on the 3 topics of the calls Trust in IT Systems

Semantic Systems and Services

Visual Computing

starting from what I research(ed) on

There will be people submitting projects, people evaluating projects: I want to tell you what I think would be more beneficial as research (and what less).At least give you food for thought ignite discussion -

Who am I

PhD in Trust Metrics in Decentralized Recommender Systems from University of Trento (2006)Since April 2008, Head of SoNet research group at Bruno Kessler Foundation (FBK), Trento, ItalyFocus is Social Networking

6 people

Bruno Kessler Foundation

~400 researchers (IT,Microelectronics,...)

Funded by Autonomous Province of Trento, North-East Italy www.fbk.eu

Not only SoNet group! ;)Data and Knowledge Management http://dkm.fbk.eu (Semantic Systems)

Web of Data http://wed.fbk.eu (Semantic Services)

Interactive interfaces http://i3.fbk.eu (Visual Computing)

Predictive Models for Biomedicine & Environment http://mpba.fbk.eu (Visual Computing)

Security and Trust http://st.fbk.eu/ (Trust in IT)

OUTLINE

Research on Trust in Recommender Systems as motivating example

Research on Social Networking at SoNet

Promising directions for Trust in IT Systems and Semantic Systems and Services

Trust

My definition of Trust: explicit rating of a user on another user about the perceived quality of the user's characteristics

Ex: I trust Mena as 0.9

Trust as social relationship and NOT about security (later I touch soft security)

Trust usage for real

Explicit trust statement I trust Mena as 0.9 (in [0,1])

E-marketplaces: Ebay.com, Epinions.com, Amazon.comSocial Network Sites: Facebook, Twitter, Flickr, ...Job sites: LinkedIn, Ryze, News sites: Slashdot.org, Kuro5hin.orgP2P networks: eDonkey, Gnutella, JXTAOpen Source Developers communities: Advogato, Affero, GithubHospitalityclub, couchsurfing: host in your house unknown people!Network of personal weblogs (blogroll)Semantic Web: FOAF (Friend-Of-A-Friend), XFNGoogle (and Yahoo!): TrustRank, PageRank

[1] P. Massa (2006). A survey of trust use in current real systems. In "Trust in E-services: Technologies, Practices and Challenges".

Trust Statement

ME

Mena

0.9

Explicit trust statement I trust Mena as 0.9 (in [0,1])

A node is a user.

A direct edge is a trust statement

Trust Network

ME

Mena

0.9

Doc

1

0

Cory

Ben

0.6

Mary

1

- weighted (0=distrust, 1=max trust)

- asymmetric

- subjective

A node is a user.

Properties of Trust:

A direct edge is a trust statement

0.2

Aggregate all trust statements Trust Network (a social network with trust as social relationship)

Trust Network

ME

Mena

0.9

Doc

1

0

Cory

Ben

0.6

Mary

1

What can you do with a Trust network?

Social Network Analysis (SNA):Computing centrality, indegrees, Powerlaws for unveiling the Topology of the network

What I did?Focusing on trust metrics

0.2

Trust Metrics

ME

Mena

0.9

Doc

1

Cory

0.2

?

?

Ben

0.6

Mary

1

Trust Metric:

Uses existing edges for predicting valuesof trust for non-existing edges.

Thanks to trust propagation, if you trust someone, then you have some degree of trust in anyone that person trusts.

0

PageRank: a trust metric?

Nodes are web pages, Edges are links (not weighted).PageRank (Google) computes the importance of every single page based on number and quality of incoming edges...So, YES: PageRank is a trust metric.

Webpage

Webpage

Webpage

Webpage

Webpage

Webpage

Imagine the web as atrust network

TM perspective: Local or Global

Global Trust Metrics:

Reputation of user is based on number and quality of incoming edges. Bill has just one predicted trust value (0.5).

PageRank (eBay, Slashdot, ). Work bad for controversial people (Bush)

Local Trust Metrics

Trust is subjective --> consider personal views (trust Bill?)

Local can be more effective if people are not standardized.

ME

Mena

1

Doc

1

Mary

Bill

1

0

How much can Bill be trusted? On average (by the community)? By Mary? And by ME?

People A trusts canbe totally different frompeople trusted by B

PageRank is Global.For web pages it worksenough well butproblems with High controversial topicsabort or jew

I tend to useReputation for this average trustTrust for the personal prediction.

Bill is Bill Gates

Global trust metricstend to standardize opinions

Global vs Local Trust Metrics

Global vs Local Trust MetricsObjective vs Subjective

Neutral Point Of View vs Your personal POV

Tyranny of the majority vs daily me/echo chambers

Trust in IT: TMs 4 Hard vs Soft Security?Soft security [2]: protects something from harm in quiet and unobtrusive ways, often invisibly and after the fact, rather than with visible barriers before the fact.

Ex: Ad-hoc, fluid, on-the-fly file permissions

[2] L. Rasmusson, S. Jansson. Simulated Social Control for Secure Internet Commerce. New Security Paradigms Workshop. ACM, 1996

Trust in Recommender Systems

How Trust Metrics are used in Recommender Systems (ex: Amazon)?

Recommend items (ex: books) appreciated by users you may trust (according to the chosen Trust Metric),

instead of recommending items appreciated by similar users (Collaborative Filtering)

Massa PhD Thesis Conclusions

Experiments on real data crawled from Epinions.com~132K users, ~14M items ratings, ~841K trust statements (positive and negative)

Trust-aware RSs smaller errors, higher coverage, especially for cold start users [3]

Local TMs very effective, especially on controversial people (>20%!) [4]

[3] P. Massa, P. Avesani (2007). Trust-aware Recommender Systems. ACM Recommender Systems Conference, Minneapolis, Minnesota, USA.[4] P. Massa, P. Avesani (2007). Trust metrics on controversial users: balancing between tyranny of the majority and echo chambers. International Journal on Semantic Web and Information Systems (IJSWIS).

Generalizing suggestions

Key points of this research on Trust-aware Recommender Systems:Open Web

Real data from real users

Share the data!

I released all the collected datasets at http://www.trustlet.orgEpinions.com, Advogato.org,

Also good for improving visibility of your research!

Nowadays data are starting to become available, mainly because of electronic trails we leave on Social Network Sites

OUTLINE

Research on Trust in Recommender Systems as motivating example

Research on Social Networking at SoNet

Promising directions for Trust in IT Systems and Semantic Systems and Services

Social Networking

Social Network Sites [5]: Facebook, Twitter,

SoNet group at FBK focuses on this

[5] boyd, d. m., & Ellison, N. B. (2007). Social network sites: Definition, history, and scholarship. Journal of Computer-Mediated Communication, 13(1), article 11.

Wikipedia as a social network

The peak of User generated content!SoNet focus is on Wikipedia as SN

Millions of users!!!

We work on the social part of Wikipedia, not the content part!

User talk page http://en.wikipedia.org/wiki/User_talk:Phauly

User talk page http://en.wikipedia.org/wiki/User_talk:Phauly

0.6

User talk page http://en.wikipedia.org/wiki/User_talk:Phauly

0.6

Shell

1

Phauly

User talk page http://en.wikipedia.org/wiki/User_talk:Phauly

0.6

Shell

1

Phauly

User talk page http://en.wikipedia.org/wiki/User_talk:Phauly

0.6

Shell

1

Phauly

Martin

1

User talk page http://en.wikipedia.org/wiki/User_talk:Phauly

0.6

Public conversations!Real data!

Shell

1

Phauly

Martin

1

ME

Mena

9

Doc

96

1

Cory

Ben

6

Mary

16

2

Directed and Weighted social network of who talks to whom on Wikipedia

Vec.wikipedia.org: just 922 nodes!

En.wikipedia.org social network has millions of nodes!

SoNet research lines on Wikipedia

Structural properties of different Wikipedia social networks (SNA)

How are talk pages used by different group of users: content analysis on Venetian Wikipedia

Comparing different ways of extracting Wikipedia social network

(future) Longitudinal: evolution in time of a Wikipedia social network

Why talk about Wikipedia SN?

Interesting! ;)

Neutral Point Of View (NPOV) tyranny of the majority?But we see edit wars, personal POVs, conflicts of interests

Trust metrics for personalizing content on wikipedia?

Soft security is how permissions are managed on Wikipedia: lessons for Trust in IT?

In few slides, I talk about Semantic services thanks to Wikipedia: DBPedia

Why did I talk about Wikipedia social network research?

It's another example of research:Open web

Real data from real people

SoNet research on Enterprise2.0

We explored Enterprise2.0, created an open source platform Taolinhttp://taolin.fbk.eu

And did research on its usage in FBK and relationships with social capital [6]

BUT we dropped this lineNO Open web: Intranet!

NO Real data from real people: few users!

[6] An Empirical Analysis on Social Capital and Enterprise 2.0 Participation in a Research Institute (2010). Asonam, Conf. on Advances in Social Networks Analysis and Mining.

By the way, I assume Wikipedia as the prototype of the organization of the futureHorizontal

Ad-hoc, rules/policies are negotiated continuously

Soft security, instead of Hard security [2]Messier but is not reality a mess?

[2] L. Rasmusson, S. Jansson. Simulated Social Control for Secure Internet Commerce. New Security Paradigms Workshop. ACM, 1996

OUTLINE

Research on Trust in Recommender Systems as motivating example

Research on Social Networking at SoNet

Promising directions for Trust in IT Systems and Semantic Systems and Services

Going back to open web and real data,Don't invent some new ways of thinking/speaking and expect people to adopt it!I propose to change all the web into this new format, then we will be able to do lots of things ...

If all the organizations would use this tool, then ...

Look for what is already available on the Web, build on it, look at it with different eyes.

Going back to open web and real data,Don't invent some new ways of thinking/speaking and expect people to adopt it!I propose to change all the web into this new format, then we will be able to do lots of things ...

If all the organizations would use this tool, then ...

Look for what is already available on the Web, build on it, look at it with different eyes.

Ex: billions of links were already there when Google founders saw them and used them for improving search engines!PageRank as 1 of 3 examples in the original definition of Web2.0 by Tim O'Reilly (2004)

Other examples of this (relevant for Semantic Systems and Services)DBPedia.orgInstead of asking people to express knowledge in RDF, automatically extract knowledge (in form of RDF triples) from Wikipedia!

Then SPARQL it (ex: People who were born in Berlin before 1900)

Another example of research:Open Web (from Web, to Web: mashable!)

Real data from real users (info was there!)

More examples

Other examples of this (relevant for Semantic Systems and Services)Microformats / RDFaBoth looked into what is there (Web) and propose small/achievable changes

Another example of research:Open web

Real data from real people

hReview example

Microformat for reviews of items (and ratings): for Trust-aware Rss!

5 out of 5 stars Crepes on Cole is awesome Reviewer: Tantek - April 18, 2005 Crepes on Cole is one of the best little creperies in San Francisco. Excellent food and service. Plenty of tables in a variety of sizes for parties large and small. Window seating makes for excellent people watching to/from the N-Judah which stops right outside. I've had many fun social gatherings here, as well as gotten plenty of work done thanks to neighborhood WiFi. Visit date: April 2005 Food eaten: Florentine crepe

Linked Data

Other examples of this (relevant for Semantic Systems and Services)LinkedData.org

Instead of asking people to express knowledge in RDF, transform available datasets! And link them!Link your research and data to what is already existent (The essence of the Web is the link!)

May 2009: 4.2 billion RDF triples, interlinked by around 142 million RDF links.

Conclusions - Suggestions

Lots of data are there and comingSocialNetworkSites have APIs for exporting data

data.gov, data.gov.uk and similar initiatives worldwide

Don't make unrealistic assumptions

Look for what is available (Web)Possibly with different glasses

Propose projects for improving the open Web, and used by real users:Wrt Trust in IT, Semantic Systems and Services

Interested in collaborating with SoNet or other FBK groups? Get in touch!Now or at http://sonet.fbk.eu

Thank you!Questions?

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