StarLion: Auto-configurable Layouts for Exploring Ontologies

1. StarLion: Auto-configurable Layouts forExploring Ontologies Stamatis Zampetakis, Yannis Tzitzikas, Asterios Leonidis, and Dimitris Kotzinos Institute of Computer Science, FORTH-ICS, Greece, and Computer Science Department, University of Crete, Greece

2. Outline • Motivation • StarLion • Exploration Method • Layout Algorithm • Ontology Dependencies • Conclusion ESWC'10 StarLion:Auto-configurable Layouts for Exploring Ontologies

3. Motivation • It is difficult to understand a big RDFS ontology, even if it is visualized (here as a labeled directed graph) ESWC'10 StarLion:Auto-configurable Layouts for Exploring Ontologies

4.  Exploration through Star Views StarView on class Actor with radius 1 • We propose exploring gradually the ontology through StarViews • the 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 ESWC'10 StarLion:Auto-configurable Layouts for Exploring Ontologies

5. Exploration through Star GraphsExample Cidoc CRM Ontology ESWC'10 StarLion:Auto-configurable Layouts for Exploring Ontologies

6. Exploration through Star GraphsExample (cont) Click on E30 Right StarView On Class Actor with Radius 1 StarView on E39 Actor with Radius = 1 ESWC'10 StarLion:Auto-configurable Layouts for Exploring Ontologies

7. Exploration through Star GraphsExample (cont) StarView on Class Right with radius 1 StarView on E30 Right with Radius = 1 ESWC'10 StarLion:Auto-configurable Layouts for Exploring Ontologies

8. Exploration through Star GraphsExample (cont): Increasing the Radius StarView on E30 Right with Radius = 2 StarView on Class Right with radius 2 ESWC'10 StarLion:Auto-configurable Layouts for Exploring Ontologies

9. Exploration through Star GraphsExample : Data Visualization • StarViews can also be used for data exploration • data usually come in big volumes which cannot be visualized altogether ESWC'10 StarLion:Auto-configurable Layouts for Exploring Ontologies

10. How to layout these graphs? Observations and Requirements • Every 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 ESWC'10 StarLion:Auto-configurable Layouts for Exploring Ontologies

11. A force-directed placement algorithm for RDFS We view an RDF schema as a mechanical system worksAt Person company Person company subClassOf subClassOf Manager Secretary Manager Secretary Magnet Magnetic Field Electrical Repulsion ESWC'10 StarLion:Auto-configurable Layouts for Exploring Ontologies

12. A force-directed placement algorithm for RDFS >Configuration •  Our approach • A toolbar for relative configuration • A “Magic button” • quality metrics and automatic configuration • FDPA has three parameters that affect the produced layout • Km – magnetic field strength • Ke – repulsion strength • L – spring length ESWC'10 StarLion:Auto-configurable Layouts for Exploring Ontologies

13. Configuring the ParametersToolbar for Relative Configuration ESWC'10 StarLion:Auto-configurable Layouts for Exploring Ontologies

14. Configuring the ParametersThe “Magic Button” • It measures the quality of the layout based on two metrics • Verticality of specialization hierarchies and • Layout area • Then it re-adjusts the configuration parameters for improving the layout ESWC'10 StarLion:Auto-configurable Layouts for Exploring Ontologies

15. Configuring the ParametersThe “Magic Button”> Example The layout with a simple application of the FDPA without any configuration ESWC'10 StarLion:Auto-configurable Layouts for Exploring Ontologies

16. Configuring the ParametersThe “Magic Button”> Example After 1 application of the FDPA with automatic configuration ESWC'10 StarLion:Auto-configurable Layouts for Exploring Ontologies

17. Configuring the ParametersThe “Magic Button”> Example After 2 applications of the FDPA with automatic configuration ESWC'10 StarLion:Auto-configurable Layouts for Exploring Ontologies

18. Visualization of Ontology Dependencies • Ontologies usually extend other ontologies • In most cases visualizing parts of the related ontologies is crucial for the understanding of the main ontology • Our Approach We support three options for the visualization of an ontology’s dependencies • Direct Dependencies: Main ontology + Only the directly connected elements from the other related ontologies • Transitive Dependencies: Main ontology + Directly connected elements from the other related ontologies along with their superclasses • Full Dependencies: Visualize all related ontologies entirely ESWC'10 StarLion:Auto-configurable Layouts for Exploring Ontologies

19. Visualization of Dependent Namespaces> Example Example: Cidoc CRM Ditital Ontology extends Cidoc CRM Ontology adding six new classes and a few properties Cidoc CRM Ontology Extends By visualizing Cidoc CRM Digital Ontology alone we get: Cidoc CRM Digital Ontology By visualizing Cidoc CRM Digital Ontology taking into account its dependency we get. ESWC'10 StarLion:Auto-configurable Layouts for Exploring Ontologies

20. Conclusion • In 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 ESWC'10 StarLion:Auto-configurable Layouts for Exploring Ontologies

21. Thanks for your attention ESWC'10 StarLion:Auto-configurable Layouts for Exploring Ontologies