December 1, 2006 Florence http://www.sekt-project.com/ 1

Dynamic Aspects of SEKT Legal Ontologies

Zhisheng Huang, Stefan Schlobach, Frank van Harmelen

Vrije University Amsterdam

Nuria Casellas and Pompeu Casanovas

Universitat Autonoma de Barcelona

December 1, 2006 Florence http://www.sekt-project.com/ 2

Outline

• SEKT Legal Ontologies

• Ontology Versioning: Motivation

• Prototype of MORE (Multi-version Ontology REasoner)

• Quantitative/Qualitative Analysis

• Conclusion

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SEKT Legal Case Study

•Design an intelligent system to help new judges with their practical problems:

• Intelligent FAQ system using Semantic Web technologies

•Connect the iFAQ system with the existing judgments

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Ontologies used in Legal Case

• OPJK (Ontology of Professional Judicial Knowledge)• 104 classes, 567 instances

• Topic ontologies:• QTO (Questions Topic Ontology)

• 17 topics

• JTO (Judgments Topic Ontology)• 30 topics.

• Judgment Ontology• 15 terms, integrated in PROTON

See Mercedes’ talk tomorrow for details.

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OPJK and Versioning• Modelled from the questions extracted from

the ethnographic survey• Aprox. 850 questions, 700 terms

• OPJK was being built extracting relevant concepts and relations from one question at a time (grouped in subdomains)

• There are a lot of versions as additions took place and modifications were required during modeling for keeping track of OPJK for it's changes.

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Multi-versioning: Why

• Change Recovery: allow the possibilities for the developers to withdraw or adjust the changes to avoid unintended impacts.

• Compatibility: Ontology users may prefer an earlier version with less resource requirement to a newer version with higher resource requirement.

• Change Tracking: Keep track of ontology changes.

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The Idea of Versioning

• Version Spaces: • Models resulting from changes are stored separately • Models and change operations form a graphcalled

Version Space• Data is accessed through the “right” version

v1 v3

v2 v4

v6

v5

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Managing Version Spaces

• Idea: Enable Administrator to ask questions about the version space

• Combine Reasoning: • Ontologies: DL reasoner (RACER) • Version Space: Modal Logic

• Principle: • Each Ontology is a possible world • Truth of statements in a state is determine by

the DL reasoner

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Abstract Use Cases

• Semantic Change Log (Temporal logic)• Summary of changes in the deductive closure

• Compatibility Checking (Temporal logic)• Compare results of queries against expected

answers

• Version Selection (Hybrid Logic)• Check versions for certain required statements

• Version Planning (Dynamic Logic)• Simulate the impact of possible changes

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Simplifying Assumptions

• Linear Time Temporal Logic• Linear Version Space• Operators

• Conjunction, Negation, PreviousVersion, AllPriorVersions

• Pre-defined Statement predicates• Child-of, parent-of,• Any other RACER function..

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Linear Time Logic LTLm

• Operators: • Boolean operators: negation, conjunction, etc.• Temporal operators (Backlooking operators)

• Prev : holds in the previous version• P: holds in a prior

version(Sometimes in the past)• H: holds in all prior versions (Always

in the past) S: always holds in the prior versions

since holds in a prior version

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Semantics

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Reasoning Queries

: holds in the current version Prev : holds in the current

version but no in the previous version.

P: incompactible (with respect to ).

H : holds only in the current version, it never holds before.

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Reasoning Query: stable change

• Once is changed, it is never changed again.

S (H).

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Reasoning Query: last version I

holds at the last version in which holds .

S (Prev( ))

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Effect Space

• Effect space is the set of all possible semantic relations in a version space.

• In MORE, we consider effect spaces which are characterized by the new/obsolete/invariant relation on concepts/roles/individuals on a version space.

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Retrieval Queries

• child/parent/descendant/ancestor concept relations

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The MORE System

• Functionality• Temporal Reasoning Queries• Ontology Comparison Queries:• Versioning Retrieval Queries• Ontology Data format: OWL, RDF/RDFS

and DIG

• http://wasp.cs.vu.nl/sekt/more

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Dynamic Aspect: New

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Dynamic Aspect: Stability

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Dynamic Aspect: Nonmonotonicity

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New at Concept Level

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Stability at Concept Level

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Qualitative Evaluation I

• Stable change of OPJK: S (H).

descendant(Fuerzas_de_Orden_Público, Objeto) S (H descendant(Fuerzas_de_Orden_Público,

Objeto) ).

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Qualitative Evaluation II

• Last version detection:

S (Prev( ))

descendant(Fuerzas_de_Orden_Público, Organización) S (Prev

descendant(Fuerzas_de_Orden_Público, Organización) descendant(Organización, Grupo)).

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Conclusions

• We studied the properties of the overall versioning space by checking for stability, novelty and monotonicity of the process.

• More detailed analysis on dynamic aspects at concept level

• We provided an initial case study on the stability of change in the versioning space using the power of the temporal logic which underlies MORE.