Result Clustering for Keyword Search on Graphs Madhulika Mohanty - - PowerPoint PPT Presentation

Result Clustering for Keyword Search on Graphs

Madhulika Mohanty

Supervisor: Dr Maya Ramanath

• Common data formats

across the Web

• Easily interpretable by

machines → “Web of data”

Linking Open Data cloud diagram, by Richard Cyganiak and Anja Jentzsch. http://lod-cloud.net/

LINKED DATA

• Collection of knowledge bases.
• All the knowledge bases are interlinked.
• Represented as RDF.
• RDF : Resource Description Framework
• Data model to represent structured

data

• Triples: <subject> <predicate> <object>
• Example:

<Tom_Hanks> <ActedIn> <Cast_Away> <Tom_Hanks> <ActedIn> <Forrest_Gump>

Tom Hanks Cast Away ActedIn

Sample YAGO graph1

1 http://www.mpi-inf.mpg.de/departments/databases-and-information-systems/research/yago-naga/yago/

Querying graphs

• SPARQL queries – structured queries

– Structured results – eg. Graph databases like Neo4j

• Natural Language queries → SPARQL

→ Structured results

• Relationship queries – unstructured text

Relationship queries

• Unstructured text, like Google.
• Answers are relationships among queried entities.
• More popularly known as “Keyword Search”.
• Why Keyword Search?

– Make graphs query-able by casual users. – Find interesting relationships – even surprise

discoveries.

Jeff Weiner Mark Zuckerberg

Jeff Weiner Mark Zuckerberg

I bet you know this..

Jeff Weiner Mark Zuckerberg

Now that's interesting!!

Bill Gates Nobel Prize winner - Edwin G. Krebs Mausam 14th Dalai Lama

Another interesting one..

Bill Gates Nobel Prize winner - Edwin G. Krebs Mausam 14th Dalai Lama Honorary Doctorate Honorary Doctorate Faculty Doctorate

Another interesting one..

Tom Hanks Robin Wright Forrest Gump

A c t e d I n Acted In

Cast Away

A c t e d I n

Movie

IsA I s A

Actor

I s A IsA

Daniel Craig The Girl with the Dragon Tattoo

A c t e d I n Acted In IsA IsA

Rooney Mara

I s A Acted In

Larry Crowne

Acted In I s A

Casino Royale

ActedIn

2011

InYear

InYear 2000 2006 1994

InYear InYear InYear IsA

Movie dataset graph

Tom Hanks Robin Wright Forrest Gump

A c t e d I n Acted In

Cast Away

A c t e d I n

Movie

IsA I s A

Actor

I s A IsA

Daniel Craig The Girl with the Dragon Tattoo

A c t e d I n Acted In IsA IsA

Rooney Mara

I s A Acted In

Larry Crowne

Acted In I s A

Casino Royale

ActedIn

2011

InYear

InYear 2000 2006 1994

InYear InYear InYear IsA

Searching for 'Hanks Wright'

Movie dataset graph

Tom Hanks Robin Wright Forrest Gump Acted In Acted In Cast Away A c t e d I n Movie I s A IsA Actor IsA I s A Daniel Craig The Girl with the Dragon Tattoo Acted In Acted In IsA IsA Rooney Mara IsA A c t e d I n Larry Crowne A c t e d I n IsA Casino Royale ActedIn 2011 I n Y e a r InYear 2000 2006 1994 InYear I n Y e a r I n Y e a r I s A

Tom Hanks Robin Wright Forrest Gump Acted In Acted In Cast Away A c t e d I n Movie I s A IsA Actor IsA I s A Daniel Craig The Girl with the Dragon Tattoo Acted In Acted In IsA IsA Rooney Mara IsA A c t e d I n Larry Crowne A c t e d I n IsA Casino Royale ActedIn 2011 I n Y e a r InYear 2000 2006 1994 InYear I n Y e a r I n Y e a r I s A

Tom Hanks Robin Wright Forrest Gump

A c t e d I n Acted In

Cast Away

A c t e d I n

Movie

IsA I s A

Actor

I s A IsA

Daniel Craig The Girl with the Dragon Tattoo

A c t e d I n Acted In IsA IsA

Rooney Mara

I s A Acted In

Larry Crowne

Acted In I s A

Casino Royale

ActedIn

2011

InYear

InYear 2000 2006 1994

InYear InYear InYear IsA

Tom Hanks Robin Wright Forrest Gump

A c t e d I n Acted In

Cast Away

A c t e d I n

Movie

IsA I s A

Actor

I s A IsA

Daniel Craig The Girl with the Dragon Tattoo

A c t e d I n Acted In IsA IsA

Rooney Mara

I s A Acted In

Larry Crowne

Acted In I s A

Casino Royale

ActedIn

2011

InYear

InYear 2000 2006 1994

InYear InYear InYear IsA

• Results are trees.

Tom Hanks Robin Wright Forrest Gump

A c t e d I n Acted In

Cast Away

A c t e d I n

Movie

IsA I s A

Actor

I s A IsA

Daniel Craig The Girl with the Dragon Tattoo

A c t e d I n Acted In IsA IsA

Rooney Mara

I s A Acted In

Larry Crowne

Acted In I s A

Casino Royale

ActedIn

2011

InYear

InYear 2000 2006 1994

InYear InYear InYear IsA

• Results are trees.
• There should exist interconnection

between all pairs of keyword nodes.

Keyword Search in a Graph structured data

Given a set of query keywords,Q=k1,k2,.....,kn and a graph G=(V , E);find top- K minimal answer trees A1, A2,...., Ak

• rdered by their relevance score.

Query

Query

Research Areas

Query

Research Areas

Efficiency

Query

Research Areas

Efficiency

• Ranking of results
• Quality of results

Query

Research Areas

Efficiency

• Ranking of results
• Quality of results

User experience

Query

Research Areas

Efficiency

• Ranking of results
• Quality of results

User experience

Searching for 'Rekha Bachchan'

18 such results

Searching for 'Rekha Bachchan'

18 such results

Searching for 'Rekha Bachchan'

Different contexts

User experience

• All kinds of results shown.
• Multiple results of same type. Eg. Amitabh and

Rekha were co-actors in multiple movies.

– Most of them ranked high. – User is forced to scroll through all

before finding new answers.

• Results with different contexts.

– User might completely miss some

information.

User experience

• All kinds of results shown.
• Multiple results of same type. Eg. Amitabh and

Rekha were co-actors in multiple movies.

– Most of them ranked high. – User is forced to scroll through all

before finding new answers.

• Results with different contexts.

– User might completely miss some

information.

• One way to deal with it – Clustering similar

results.

Result clustering

• Cluster similar results together.
• Rank the clusters.
• Show one representative per cluster

(Highest Ranked Tree).

– User may click it and see all results.

• Advantages:

– Can be used with any existing

Keyword Search algorithm.

– Provides user with a bird's eye view

• ver the results.

– Easy to analyze interesting patterns.

Result clustering (contd.)

Isomorphism based Tree Edit distance based Language Model (LM) based

• Cluster isomorphic

trees together.

• Two trees need to

have exact same structure to be clustered together.

• Ends up generating

too many clusters.

• Clustering based on tree-

edit distance with a similarity threshold of 0.9

• Cannot differentiate

different contexts like the “Amitabh Bachchan” and “Bol Bachchan” case.

• Agglomerative Complete Link

Clustering

• Each tree represented as a

LM.

• JS Divergence as similarity

measure.

Clustering Quality measure: User evaluation

• Dataset: IMDB
• User evaluations over 20 manually

selected queries.

– Varying from 2-6 keywords in each.

• User was not aware of the underlying

technique.

• Asked to rate on a scale of 1-5:

– How similar trees are within a cluster? – How dissimilar trees are between

different clusters?

Thank you