D. Kehagias, I. Papadimitriou, D. Tzovaras (CERTH/ITI)J. Hois, J. Bateman (University of Bremen)

A Methodological Approach for A Methodological Approach for Ontology Evaluation and RefinementOntology Evaluation and Refinement

2nd ASK-IT International Conference2nd ASK-IT International Conference

22ndnd ASK-IT International Conference, 26-27 June 2008, Nuremberg ASK-IT International Conference, 26-27 June 2008, Nuremberg

Important aspects have been considered on restructuring

Hierarchy/Taxonomy Property Structure Similar Concepts Subtraction of Modules Documentation/Visualization Ranges for Object Properties Disjointness Restrictions Naming Conventions

ASK-IT Ontologies Revision ASK-IT Ontologies Revision

22ndnd ASK-IT International Conference, 26-27 June 2008, Nuremberg ASK-IT International Conference, 26-27 June 2008, Nuremberg

Hierarchy/TaxonomyHierarchy/Taxonomy

Flat concept hierarchy More tree-like structure

110 concepts on the same level 67 concepts on the same level

Unexploited grouping possibilities for concepts of similar kind

Better grouping of concepts, more clear re-organized structure

Level of abstraction not always taken into account

Same hierarchy-level for concepts of same abstraction-level

Existence of branches differently structured (depth, breadth, etc.)

More balanced (equally developed) hierarchy

Before After

22ndnd ASK-IT International Conference, 26-27 June 2008, Nuremberg ASK-IT International Conference, 26-27 June 2008, Nuremberg

ExamplesExamples

Bar

Cafe

Restaurant

Bar

Cafe

Restaurant

FoodAndDrink

Climate

MeanTemperature

Temperature

Weather

MeanTemperature

Temperature

Climate

22ndnd ASK-IT International Conference, 26-27 June 2008, Nuremberg ASK-IT International Conference, 26-27 June 2008, Nuremberg

Property StructureProperty Structure

No property structure A restructuring has been realized

290 properties not hierarchically grouped at all

Datatype properties on the same top level have been reduced from 198 to 86

Unexploited grouping possibilities for equal domain properties

Better grouping of equal domain properties, more concrete structure

Further information might be interesting New properties have been added for better description

Before After

22ndnd ASK-IT International Conference, 26-27 June 2008, Nuremberg ASK-IT International Conference, 26-27 June 2008, Nuremberg

ExamplesExamples

dayValue

nightValue

minValue

maxValue

MeanTemperature

Domain:

Temperature

Domain:

generalInfoOfClimate

generalInfoOfWeather

generalInfoOfMeanTemperature

generalInfoOfTemperature

dayValuenightValue

minValuemaxValue

cloudy

rainy

snowy

sunny

22ndnd ASK-IT International Conference, 26-27 June 2008, Nuremberg ASK-IT International Conference, 26-27 June 2008, Nuremberg

Similar ontological concepts are repeated frequently

Impairments could be defined only once and their use be extended within other definitions

Re-use mechanism not applicable in OWL-DL

Future implementation in other languages, such as CASL

For example, different kinds of impaired categories (visual, hearing, wheelchair, etc.)

Unexploited possibility for combination to one module and re-using whenever necessary

Before After

Similar ConceptsSimilar Concepts

22ndnd ASK-IT International Conference, 26-27 June 2008, Nuremberg ASK-IT International Conference, 26-27 June 2008, Nuremberg

Duplicate definitions of the same concept Elimination of one definition

Existence of very similar (or almost identical) concepts

Concepts removed or merged to a single concept

Properties not used at all Properties removed

Complex ontology Reduced complexity, ontology more “clear”, compact and readable

Before After

Subtraction of ModulesSubtraction of Modules

22ndnd ASK-IT International Conference, 26-27 June 2008, Nuremberg ASK-IT International Conference, 26-27 June 2008, Nuremberg

POIS_How_to_get_there2

POIS_How_to_get_to_the_pois

POISHowToGetThere

POIHowToGetThere

General_info2

GeneralInfoForALLGeneralInfo

hasAccommodation

hasAccommodationInfohasAccommodation

mean_tmp mean_tmp

ExamplesExamples

22ndnd ASK-IT International Conference, 26-27 June 2008, Nuremberg ASK-IT International Conference, 26-27 June 2008, Nuremberg

Documentation/VisualizationDocumentation/Visualization

Poor documentation Documentation improved

Almost no comments in the ontology Comments added for most concepts (mainly higher-level ones)

Ontology difficult to use and understand Ontology easier to be applied / re-used in other applications

Examples:

Accommodation :

Climate :

A concept that models a place where someone can stay, e.g. a hotel room.

A concept that models some of the climate characteristics.

Before After

22ndnd ASK-IT International Conference, 26-27 June 2008, Nuremberg ASK-IT International Conference, 26-27 June 2008, Nuremberg

Ranges for Object PropertiesRanges for Object Properties

No range definition for some object properties Range defined for all object properties

Inconsistencies may appear Avoid inconsistencies

Before After

Examples:

hasMonth

hasWalk

Range:

Range:

Month

Walk

22ndnd ASK-IT International Conference, 26-27 June 2008, Nuremberg ASK-IT International Conference, 26-27 June 2008, Nuremberg

Disjointness RestrictionsDisjointness Restrictions

Missing disjointness conditions for some concepts

Disjointness restrictions have been reconsidered more carefully

Disjointness might not hold for some other concepts

Disjointness removed from where we might have an overlap

Before After

Examples:

Doctor

Hospital

MedicalService

DisjointSpectatorStandForHearingImp

SpectatorStand

Not disjointSpectatorStand

ForUpperLimbImp

22ndnd ASK-IT International Conference, 26-27 June 2008, Nuremberg ASK-IT International Conference, 26-27 June 2008, Nuremberg

Naming ConventionsNaming Conventions

Before After

No alignment for all concept names Alignment for reasons of clearness

For example, they end with “-Impaired”, “-Imp”, or nothing All impairment categories end with “-Imp”

Camel case and underscores mixed Camel case is always used

Plural and singular forms mixed Singular form is adopted

Property names sometimes begin with upper case or lower case letter

All property names begin with lower case letter

Examples:

Local_support_groups LocalSupportGroup

LongBench longBench

22ndnd ASK-IT International Conference, 26-27 June 2008, Nuremberg ASK-IT International Conference, 26-27 June 2008, Nuremberg

More InfoMore Info

http://askit.iti.gr/ontologyhttp://askit.iti.gr/ontology

• ASK-IT Ontology

http://www.ask-it.org/http://www.ask-it.org/

• ASK-IT Web Site