StarLion: Auto-configurable Layouts forExploring Ontologies

Stamatis Zampetakis, Yannis Tzitzikas,Asterios Leonidis, and Dimitris Kotzinos

Institute of Computer Science, FORTH-ICS, Greece, andComputer Science Department, University of Crete, Greece

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OutlineMotivationStarLion

Exploration MethodLayout AlgorithmOntology Dependencies

Conclusion

ESWC'10 StarLion:Auto-configurable Layouts for Exploring Ontologies

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Motivation It is difficult to understand a big RDFS

ontology, even if it is visualized (here as a labeled directed graph)

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Exploration through Star ViewsWe propose exploring gradually the ontology

through StarViewsthe user selects one class c as a focal point. Class c along with all

related classes in distance (radius) k from c are visualized creating Star-like graphs

StarView on class Actor with radius 1

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Exploration through Star Graphs

Example

Cidoc CRM Ontology

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Exploration through Star Graphs

Example (cont)

StarView On Class Actor with Radius 1

StarView on E39 Actor with Radius = 1

Click on E30 Right

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Exploration through Star Graphs

Example (cont)

StarView on E30 Right with Radius = 1

StarView on Class Right with radius 1

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Exploration through Star Graphs

Example (cont): Increasing the Radius

StarView on Class Right with radius 2

StarView on E30 Right with Radius = 2

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StarViews can also be used for data explorationdata usually come in big volumes which cannot be

visualized altogether

Exploration through Star Graphs

Example : Data Visualization

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How to layout these graphs?

Observations and RequirementsEvery graph has different features:

Different number of nodes, edges, isA (subclass-superclass) relations

The layout algorithm that will be used, must be configurable for adapting to every occasion

Our approach Adopt a force-directed placement algorithm

(FDPA) and focus on the configuration of its parameters

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A force-directed placement algorithm for RDFS

ESWC'10 StarLion:Auto-configurable Layouts for Exploring Ontologies

Person

company

Manager

Secretary

Person

company

Manager

Secretary

worksAt

subClassOfsubClassOf

We view an RDF schema as a mechanical system

Magnet Magnetic Field

ElectricalRepulsion

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A force-directed placement algorithm for RDFS >

Configuration FDPA has three parameters that affect the produced

layoutKm – magnetic field strengthKe – repulsion strength L – spring length

Our approach• A toolbar for relative configuration• A “Magic button”

• quality metrics and automatic configuration

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Configuring the Parameters

Toolbar for Relative Configuration

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Configuring the ParametersThe “Magic Button”It measures the quality

of the layout based on two metricsVerticality of

specialization hierarchies and

Layout areaThen it re-adjusts the

configuration parameters for improving the layout

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Configuring the Parameters

The “Magic Button”> Example The layout with a simple application of the FDPA without any configuration

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Configuring the Parameters

The “Magic Button”> Example After 1 application of the FDPA with automatic configuration

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Configuring the Parameters

The “Magic Button”> Example After 2 applications of the FDPA with automatic configuration

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Visualization of Ontology DependenciesOntologies usually extend other ontologies In most cases visualizing parts of the related

ontologies is crucial for the understanding of the main ontology

Our ApproachWe support three options for the visualization of an

ontology’s dependenciesDirect Dependencies: Main ontology + Only the directly

connected elements from the other related ontologiesTransitive Dependencies: Main ontology + Directly

connected elements from the other related ontologies along with their superclasses

Full Dependencies: Visualize all related ontologies entirely

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Visualization of Dependent Namespaces> Example

Cidoc CRM Ontology

Cidoc CRM Digital

Ontology

Extends

Example:Cidoc CRM Ditital Ontology extends Cidoc CRM Ontology adding six new classes and a few properties

By visualizing Cidoc CRM Digital Ontology alone we get:

By visualizing Cidoc CRM Digital Ontology taking into account its dependency we get.

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ConclusionIn comparison with related works and systems:

Most of them do not support variable radius in StarView

None of them uses a FDPA that takes into account the subClassOf hierarchies

Most of them do not allow configuring the FDPA parameters

They do not support auto-configuration of the FDPA parameters

They do not exploit dependencies between ontologies in the visualization

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THANKS FOR YOUR ATTENTION