with the Linked Data Cloud Vincenzo Maltese, Feroz Farazi DISI - - PowerPoint PPT Presentation

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with the Linked Data Cloud Vincenzo Maltese, Feroz Farazi DISI - - PowerPoint PPT Presentation

Oct 04, 2023 547 likes •829 views

Towards the integration of KOS with the Linked Data Cloud Vincenzo Maltese, Feroz Farazi DISI University of Trento The main message Reusing and sharing ontologies: the linked data initiative In reusing and sharing ontologies: 1. It is

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Towards the integration of KOS with the Linked Data Cloud

Vincenzo Maltese, Feroz Farazi DISI – University of Trento

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SLIDE 2

The main message

Reusing and sharing ontologies: the linked data initiative In reusing and sharing ontologies:

  • 1. It is fundamental to take into account and make explicit

their purpose and semantics

  • 2. The difference in the purpose is reflected in the difference

in the semantics and in the applications we enable

  • 3. Before integrating them, it is possible and essential to

translate them such that they have the same semantics

  • 4. To maximize reuse, publishing an ontology requires

appropriate semantics

Vincenzo Maltese The Hague - UDC seminar 2011 2

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Building a KOS can be extremely costly

  • Reuse as much as possible
  • Need: discover similar resources

and (partially) integrate them

  • Solution:
  • Manual approaches

(accurate but slow)

  • Automatic tools

(need background knowledge, need manual validation, but fast)

  • Share as much as possible
  • Need: incentives, a common

framework

  • Solution: the Linked Data

initiative

Vincenzo Maltese The Hague - UDC seminar 2011

institution

  • rganization

≡

3

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SLIDE 4

Ontologies are extremely diverse

They may differ in scope, purpose, structure, terminology, language, coverage, formality and conceptualization In sharing and reusing them, it is fundamental to take into account and make explicit:

  • The difference in the purpose (their goal)
  • The difference in the semantics (their meaning)

Vincenzo Maltese The Hague - UDC seminar 2011 4

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Real World semantics

Vincenzo Maltese

a b building Eiffel Tower

instance-of I(a) I(b)

Each term at nodes denotes a real world object or a set of objects

The Hague - UDC seminar 2011 Domain of interpretation 5

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Classification semantics

Vincenzo Maltese

a b building Eiffel Tower

NT/BT I(a) I(b)

Each term at nodes denotes a set of documents about real world

  • bjects

The Hague - UDC seminar 2011 Domain of interpretation 6

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Difference in the purpose is reflected in different semantics

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Descriptive ontologies

Vincenzo Maltese The Hague - UDC seminar 2011

a b country Italy

instance-of

c Trento

part-of

d

  • rganization

university

is-a

g University

  • f Trento

e research center

is-a

f

  • Purpose: describing a domain
  • Semantics: real world semantics

part-of

h FBK

instance-of instance-of collaborates-with 8

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SLIDE 9

Classification ontologies

Vincenzo Maltese The Hague - UDC seminar 2011

a b country Italy

NT/BT

c Trento d

  • rganization

university g University

  • f Trento

e research center f

  • Purpose: classifying, searching and browsing documents
  • Semantics: classification semantics

h FBK

RT NT/BT NT/BT NT/BT NT/BT NT/BT NT/BT

d1 d2 d3 d4

9

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Difference in the semantics affects what we can do with them

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Descriptive ontologies: typical queries

Vincenzo Maltese The Hague - UDC seminar 2011

a b country Italy

instance-of

c Trento

part-of

d

  • rganization

university

is-a

g University

  • f Trento

e research center

is-a

f

  • Give me all the countries: {Italy}
  • Give me all the organizations: {University of Trento, FBK}
  • Give me all the organizations located in Italy: {University of Trento}

part-of

h FBK

instance-of instance-of collaborates-with 11

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Classification ontologies: typical queries

Vincenzo Maltese The Hague - UDC seminar 2011

a b country Italy

NT/BT

c Trento d

  • rganization

university g University

  • f Trento

e research center f h FBK

RT NT/BT NT/BT NT/BT NT/BT NT/BT NT/BT

d1 d2 d3 d4

  • Give me all documents about countries
  • Give me all documents about Italy: {d1} or {d1, d2} or{d1, d2, d3}?

It depends! Do we expand? Are all NT/BT transitive?

12

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Making explicit the semantics allows for automation

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Descriptive ontologies: how to make them formal

Vincenzo Maltese The Hague - UDC seminar 2011

a b country Italy

instance-of

c Trento

part-of

d

  • rganization

university

is-a

g University

  • f Trento

e research center

is-a

f

Assume we use Description Logics (DL):

  • Classes correspond to concepts
  • Instances correspond to individuals
  • Is-a relations are translated into subsumption (⊑)
  • Other relations correspond to DL roles

part-of

h FBK

instance-of instance-of collaborates-with 14

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SLIDE 15

Classification ontologies: how to make them formal

Vincenzo Maltese The Hague - UDC seminar 2011

a b country Italy

NT/BT

c Trento d

  • rganization

university g University

  • f Trento

e research center f h FBK

RT NT/BT NT/BT NT/BT NT/BT NT/BT NT/BT

d1 d2 d3 d4

Assume we use Description Logics (DL):

  • Classes correspond to concepts
  • Documents correspond to individuals
  • Transitive NT/BT relations are translated into subsumption (⊑)
  • RT and non-transitive NT/BT relations correspond to DL roles

15

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Converting, integrating and reusing ontologies

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Convert before integrating ontologies

  • It is clearly not appropriate to integrate ontologies having

different semantics.

  • Given the purpose select the semantics
  • If the purpose is to classify, convert both ontologies into

classification ontologies

  • If the purpose is to describe, convert both ontologies into descriptive
  • ntologies

Vincenzo Maltese The Hague - UDC seminar 2011 17

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From descriptive to classification ontologies

  • Convert instances to classes
  • Convert instance-of, is-a and transitive part-of

into NT/BT relations

  • Convert other relations into RT relations

Hierarchies are constructed on the basis of genus-species (is-a, instance-of) and whole-part (part-of) relations [Ranganathan, 1967. Prolegomena to library classification] The process above can be easily automated There is a clear loss of information

Vincenzo Maltese The Hague - UDC seminar 2011

a b country Italy

instance-of

a b country Italy

NT/BT 18

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From classification to descriptive ontologies

  • Each class has to be mapped to either a real

world class or instance

  • Each transitive NT/BT relation has to be

converted into either an instance-of, is-a or part-of

  • Each RT relation and non-transitive NT/BT

relation has to be codified into an appropriate real world associative relation

The process above CANNOT be automated A substantial amount of human effort is required

Vincenzo Maltese The Hague - UDC seminar 2011

a b country Italy

(which relation???)

a b country Italy

NT/BT (instance or class???) 19

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Distributing schemes as descriptive

  • ntologies would ensure

maximum reusability

For those reasons Let us look at a concrete use case…

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GeoWordNet: a multilingual descriptive ontology

Vincenzo Maltese The Hague - UDC seminar 2011

Objects Quantity Classes 110,459 Instances 6,927,078 Instance-of 6,927,078 Is-a 89,266 transitive part-of 5,325 Associative relations 98,907

  • Neat separation between language and conceptual levels
  • It is currently in English and Italian
  • Built from WordNet, Italian MultiWordNet and GeoNames
  • We compute the transitive closure for both the descriptive and

classification version of the ontology

  • We use the appropriate semantics according to the task

21

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Conclusions

  • There is the need to reuse/share ontologies
  • It is fundamental to take into account and make explicit their

purpose and semantics

  • Particular attention has to be paid to the transitivity of the

relations

  • Storing ontologies in their descriptive version maximizes

reuse and effectiveness

Vincenzo Maltese The Hague - UDC seminar 2011 22

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Towards the integration of KOS with the Linked Data Cloud Thank you for your time and interest! Questions? maltese@disi.unitn.it

GeoWordNet open source: http://geowordnet.semanticmatching.org/

Vincenzo Maltese The Hague - UDC seminar 2011 23

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Extra slides

The Hague - UDC seminar 2011 Vincenzo Maltese 24

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Descriptive ontologies: how to make them formal

Vincenzo Maltese The Hague - UDC seminar 2011

a b country Italy

instance-of

c Trento

part-of

d

  • rganization

university

is-a

g University

  • f Trento

e research center

is-a

f

university ⊑ organization university(UniversityOfTrento) collaborates(UniversityOfTrento, FBK) …

part-of

h FBK

instance-of instance-of collaborates-with 25

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SLIDE 26

Classification ontologies: how to make them formal

Vincenzo Maltese The Hague - UDC seminar 2011

a b country Italy

NT/BT

c Trento d

  • rganization

university g University

  • f Trento

e research center f h FBK

RT NT/BT NT/BT NT/BT NT/BT NT/BT NT/BT

d1 d2 d3 d4

university ⊑ organization Trento ⊑ Italy Italy(d1) …

26

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SLIDE 27

Limitations of RDF and SKOS

Vincenzo Maltese The Hague - UDC seminar 2011

a b

  • rganization

University of Trento

Instance-of

c d building University of Trento

Is b ≡ d ?

RDF SKOS No support for disjointness No support for disjointness Classes can be treated as instances No distinction between classes and instances (we cannot represent documents) Transitivity of relations cannot be enforced at the level of entities We can define non-transitive NT/BT

Instance-of 27