Download - Semantic Recognition of Ontology Refactoring

Web Science & Technologies

University of Koblenz ▪ Landau, Germany

Semantic Recognition of Ontology Refactoring

Gerd Gröner

Fernando Silva Parreiras

Steffen Staab

ISWC2010, Shanghai

Gerd Grö[email protected]

ISWC 20102

WeST

Distributed Development of Ontologies

ChangeOntology

Version V1 ChangeOntology

Version V2Ontology

Version V3

ChangeOntology

Version V4

Change

Change ...

...

No change logs!


ISWC 20103

WeST

What has changed?ontology version V ontology version V'

∆?

Compare

Recognize,analyze and explain!


ISWC 20104

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Agenda

Problem Description and Ontology Refactoring

Analyze and describe Changes

Recognize Changes

Reasoning for Comparison of Ontology Versions

Refactoring Recognition

Discussion and Conclusion


ISWC 20105

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Refactoring Scenario

Change

ontology version V

ontology version V'


ISWC 20106

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Comparison: What has changed?

ontology version V ontology version V'

Employee ⊑ PersonEmployee ⊑ ∃ project.Project (d)Employee ⊑ ∃ department.DepartmentEmployee ⊑ ∃=1 SSN.string (d)Person ⊑ ∃ name.stringPerson ⊑ ∃ address.string (d)Person ⊑ ∃ telephone.string (d)

Employee ⊑ PersonEmployee ⊑ ∃ department.DepartmentEmployee ⊑ ∃≥1 SSN.string (a)Person ⊑ ∃ name.string Person ⊑ ∃≤1 SSN.string (a)Person ⊑ ∃ contact.ContactData (a)ContactData ⊑ ∃ telephone.string (a)ContactData ⊑ ∃ address.string (a)Department ⊑ ∃ project.Project (a)


ISWC 20107

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Analyze and Describe Changes

Observation:

Is the set of axioms (V and V') helpful to recognize changes?

How can we communicate about changes?

(domain knowledge, modeling details)

Idea:

➔ Categorize Changes by Refactorings


ISWC 20108

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Refactoring Pattern

Refactoring Pattern

E.g., extract properties address and telephone

Refactoring

13 refactoring pattern

Example: Extract Class

Some properties p1, …, pn of class C should be extracted to a new class D


ISWC 20109

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Refactoring: Extract ClassV V'


Employee ⊑ PersonEmployee ⊑ ∃ department.DepartmentEmployee ⊑ ∃≥1 SSN.string (a)Person ⊑ ∃ name.string Person ⊑ ∃≤1 SSN.string (a)

Person ⊑ ∃ contact.ContactData (a)ContactData ⊑ ∃ telephone.string (a)ContactData ⊑ ∃ address.string (a)Department ⊑ ∃ project.Project (a)


ISWC 201010

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Refactoring: Pull-Up Property

V V'




ISWC 201011

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Refactoring: Move Of Property

V V'




ISWC 201012

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Recognition: Difficulties

1. (syntactical) comparison of axioms or triples in V and V'

2. purely structural comparison

➔ Semantic comparison


ISWC 201013

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Agenda

Problem Motivation and Ontology Refactoring


Comparison Problem

Solution➔ Combining Knowledge Bases➔ Version Comparison




ISWC 201014

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The Comparison Problem

Situation: Conceptual relations in each ontology (version) Same classes, e.g., Person

Goal:➔ Conceptual relation across versions

Person ⊑ ∃ address.string

V V'

Person ⊑ ∃ address.string ?


ISWC 201015

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Structural and semantic comparison: class subsumption checking to compare their extensions➔ Joint reasoning on two ontology versions to identify

conceptual relations

Problems:

How to connect them?

How to compare them?

Comparison Methods

Matching: compare class and property names and types


ISWC 201016

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Connecting two Versions

1. Matching between classes

2. Renaming of classes that appear in both versions

Person1 ⊑ ⊤Person2 ⊑ ⊤

3. Introduce a common superclass

Person1 ⊑ PersonPerson2 ⊑ Person

4. Relax range

ContactData ⊑ ∃ person . Person1 ⇒ ContactData ⊑ ∃ person . Person


ISWC 201017

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Comparison – affected axioms

Variety of modeling principles in OWL➔ Only some need to be considered:

Property restrictions:

Person ⊑ ∃ address.string

Corresponding axioms:

Person ⊑ ∃ contact.ContactData ContactData ⊑ ∃ address.string

→ Analyzes: Class expressions of property restrictions


ISWC 201018

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Comparison – affected axioms (2)

Sub- and superclasses:

➔ Only certain kinds of axioms are relevant! ➔ Next Step: Normalization to ease version comparison

Employee ⊑ PersonEmployee ⊑ ∃=1 SSN.string

Employee ⊑ PersonEmployee ⊑ ∃≥1 SSN.stringPerson ⊑ ∃≤1 SSN.string

Corresponding axioms:

→ Analyzes: Subclass axioms and property restrictions


ISWC 201019

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Normalization

Analyze axioms of class definitions of class C:

Conjunctive normal form of C:

Ĉ ≡ C1 ⊓ … ⊓ Cn ∀ i = 1 … n: C ⊑ Ci

Reduced conjunctive normal form: Ċ• Flattened nested conjunctions: A ⊓ (B ⊓ C) → A ⊓ B ⊓ C• Normalized negation: ¬D → D is a named class• B ⊑ A and A ⊔ B : A ⊔ B → A


ISWC 201020

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Reduced Conjunctive Normal Form

Uniqueness of the normal form Ċ

Ċ is reduced conjunctive normal form of Ĉ ≡ C1 ⊓ … ⊓ Cn

for each Ci one of the following condition holds:

Ci is a named class

Ci is a data type or object property restriction

Ci is a complex class definition that is neither a named superclass of C nor a property restriction


ISWC 201021

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Using the Normalization

Exploit two results

1. Only certain types of axioms are affected by the refactoring➔ Other axioms can be neglected

2. Representation in the normal form● Axioms are covered by the normal form representation● Uniqueness: class expressions Ci of C can be extracted

● Each Ci of C subsumes C

➔ Analyze changes by comparing class expressions Ci of C and C' using subsumption checking


ISWC 201022

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DiffDiff and Common Common Algorithm

Diff: Compute class expressions (superclasses) from C and C'

1. Class expressions of C in version V' but not in V

E.g.,

For each class expression A of Ċ'

If the subsumption ( A ⊑ C ) does not hold then

Class expression A belongs to the difference

2. Likewise the expressions of C in version V but not in V'

➔ Difference is computed in two steps (invert V and V'):

Reduced conjunctive normal form applies to the class expressions of the result


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Agenda

Problem Motivation and Ontology Refactoring





ISWC 201024

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Each pattern: specification of differences for comparing two versions description of conditions on these differences

Comparison algorithms: determining the different and common parts of a class in two versions Comparing class expressions of Ċ Using subsumption checking to test the conditions on the

differences


ISWC 201025

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Extract Class

D1 = { ∃ contact.ContactData } D2 = { ∃ address.string, ∃ telephone.string }

Difference (C = Person):

RC = ContactData (range of ∃ contact.ContactData)

V V'

Extracted Class:

Condition:ContactData ⊑ ∃ address.stringContactData ⊑ ∃ telephone.string are inferred in V'


ISWC 201026

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Conclusion

Described Solution:

Adopted 13 refactoring patterns and described the recognition

Realization:

Class comparison using subsumption checking Connect versions (V and V' are unaffected) Compare classes and class expressions of Ċ Only certain class expressions are relevant in the refactoring

Future Work:

Consider further refactoring patterns


ISWC 201027

WeST

Thank You!

Supported by: MOST-Project

Download - Semantic Recognition of Ontology Refactoring

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