Natural Language Interfaces to Ontologies

Danica Damljanović

danica@dcs.shef.ac.uk

University of Sheffield NLP

Outline

• NLIs to ontologies and their usability

• QuestIO – Question-based Interface to Ontologies

• Towards better usability using FREyA• Demo and evaluation

• Conclusion

210/12/09 Danica Damljanović

University of Sheffield NLP

Motivation

Large datasets such as Linked Open Data available

SPARQL/SeRQL: complex syntax: not easy to learn writing queries is error-prone task requires understanding of Semantic Web

technologies

University of Sheffield NLP

Objective

Allow domain experts to query knowledge in RDF/OWL format in a user-friendly manner

University of Sheffield NLP

Danica Damljanović

Natural Language user-friendly?

(Kaufmann and Bernstein, 2007)• Natural Language Interfaces preferred to keywords, menu-

guided, and graphical interfaces

(Linckels, 2007): • keywords preferred to NL interfaces

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6Danica Damljanović

NLIs to ontologies

University of Sheffield NLP

Error rate caused by…

• Users not familiar with the covered knowledge

• Knowledge is not available, but the system is not making that clear to the user i.e. feedback messages not helpful

• Users have assumptions/misconceptions about the system capabilities and supported language

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8Danica Damljanović

Usable NLIs to KBs: challenges

• Robustness

• Portability

• What to show?

• Understanding information need

• Habitability

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Challenging habitability problem

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Question-based Interface to Ontologies

• Robust• Zero customisation!• Easy to use: no training for

the user.• Deal with incorrectly

formulated queries• Accept queries of any

length and form.• Automatically ranks results

and shows the highest rank to the user

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NL --> SeRQL query

Filtering concepts

Ranking concepts

Query Creator

Query Execution

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An Example

1.15

1.19

compare

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FREyA (Feedback, Refinement, Extended Vocabulary Aggregator)

• assist the user formulate the query and express his need more precisely

• Implement user-system interaction and learn from it

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Example 1

geo:City

geo:State new york

POC

POC

population

geo:cityPopulation

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New York is a city

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New York is a state

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POC

POC

POC

state

area geo:stateArea geo:State

geo:isLowestPointOf

lowest point

Example 2

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Demo

• http://gate.ac.uk/freya

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In lab evaluation• Mooney dataset: geography of the United States

• Relatively small ontology

• 250 questions

• require a high level of understanding of semantic meaning

• Recall and precision:

• 76% when we identify only the answer type correctly (first POC in the question)

• Expected: ~91% when we include all POCs from the question and add more refined suggestions (such as max or min for datatype properties of type number)

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Next steps

• Improvement of the learning mechanism

• User-based evaluation

• Trying it with some other datasets

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Thank you!

• Questions?