Ontology design patterns

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Ontology design patterns

• Value sets
• QCRs
• N-ary relations
• Part-whole relations
• Cleaning hierarchies

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Exercise

• We want to describe the color of historic clothes
  in a museum
• Hot to specify the range of hasColor?
• Do you use a OWL restriction or a RDFS range
  definition to define constraint?

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Value sets for specifying values

• A quality SexValue
• Individuals for each value
• male, female
• Values all different (NOT assumed by OWL)
• Value type is enumeration of values
• SexValue male, female
• A functional property hasSex
• MaleAnimal Animal and hasSex is male

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Value Partitions example Age Group

• How to represent the values for Age Group?
• Option
• specify Child, Toddler, etc. as subclasses of
  AgeGroup
• Specify age-group values as instances of the
  relevant age-group class
• exMyAgeGroup rdftype exAdult .
• Main advantage flexibility

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OWL restrictions and why rdfsdomain/range is
considered harmful
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Example restriction red wines must have a red
color

• RedWine
• a owlClass
• rdfssubClassOf
• a owlRestriction
• owlonProperty color
• owlhasValue redxsdstring
• .

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OWL vs. UML class modeling

• OWL properties vs. UML associations attributes
• OWL properties have a direction
• OWL properties are binary relations
• OWL\properties are first-class citizens (global
  scope)
• OWL classes vs. UML classes
• OWL classes have no operations
• OWL classes can have sufficient conditions
• Primitive vs. defined classes

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OWL restriction Artefact
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Ontological commitment

• Each statement in an ontology commits the user to
  a particular view of the domain.
• Over-commitment definition in an ontology is
  stronger than needed.
• Property restrictions on classes commit to less
  then rdfsdomain/range constraints
• When in doubt, choose the option with the least
  commitment
• Be aware of cultural biases!

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OWL restriction Artist (1)
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OWL restriction Artist (2)
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Ontologies and data models

• Ontologies live in an open, distributed world
  data models in a closed world
• Danger of overcommitment is therefore much larger
  in ontologies
• Writing a model in OWL does not make it an
  ontology
• The ontology should be shared

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Qualified cardinality constraints
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Use case

• SelectionCommittee
• a owlClass
• rdfssubClassOf
• a owlRestriction
• owlonProperty committeeMember
• owlallValuesFrom Person
• .
• How can we define that a selection committee must
  have two female members?

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Qualified cardinality restrictions (QCRs)

• Restriction on the number of values of a certain
  type (hence qualified)
• owlsomeValuesFrom is an example of such a
  constraint
• cardinality of 1 or more of a certain type of
  value
• Typically used to specify the component types in
  some part-of structure

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Workaround for QCRs

• No direct way of modeling this in OWL
• Workaround
• Define a subproperty of the property on which you
  want to define a QCR
• Define a value constraint (using either
  owlallValuesFrom or rdfsrange) and a
  cardinality constraint on the subproperty
• Cumbersome for complex part-whole relations

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Example workaround

• SelectionCommittee a owlClass
• rdfssubClassOf
• a owlRestriction
• owlonProperty committeeMemberFemale
• owlallValuesFrom FemalePerson
• rdfssubClassOf
• a owlRestriction
• owlonProperty committeeMemberFemale
• owlminCardinality "2"xsdint .

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Part-whole relations

• Simple part-whole relations in OWL Ontologies
• A foundation for composition

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Part-whole relations

• Common in many domains
• Human body, cars, installations, documents
• Different from the subclass/generalization
  relation
• No built-in modeling constructs in OWL
• Different types of part-whole relations exist
• With important semantic differences
• Mereology theory of part-whole
• meros is Greek for part

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UML Aggregation

• Aggregation denotes a binary association in which
  one side is an "assembly" and the other side a
  "part".
• "Assembly" and "part" act as predefined roles
  involved in the aggregation association.
• Cardinality of a part can be defined
• precisely one optional (0-1) many, ...
• No semantics in UML!

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Aggregation example in UML
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UML Composition

• Sub-type of aggregation
• Existence of part depends on aggregate

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Aggregation vs. generalization

• Similarities
• Tree-like structure
• Transitive properties
• Differences
• AND-tree (aggregation) vs. OR-tree
  (generalization)
• instance tree (aggregation) vs. class tree
  (generalization)

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Representing part-whole relations

• Part-whole relation is transitive
• If A is part of B and B is part of C then A is
  part of C
• But see the caveats later on
• Usually there is a a need to distinguish
• Part in a transitive sense
• Direct part

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Basic scheme

• Define a property e.g. partOf and (usually
  needed) the inverse hasPart
• Define a subproperty of part of partOf to
  represent direct parts, e.g. partOfDirect
• Choose the primary property for expressing
  part-whole part of or hasPart?
• partOf is generally more flexible. Why?

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Transitivity

• A subproperty of a transitive property is not by
  definition transitive
• Make sure you understand why
• Example direct-part properties are not transitive

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Part-whole specification with individuals

• Amsterdam a InhabitatedPlace
• partOf North-Holland .
• North-Holland a Province
• partOf Netherlands .
• Place a owlClass
• rdfssubClassOf
• a owlRestriction
• owlonProperty partOf
• owlallValuesFrom Place .

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Part-whole specification with classes

• AudioSystem hasPart
• someValuesFrom Amplifier
• someValuesFrom Loudspeaker
• someValuesFrom InputSystem
• assume CD, tuner and cassette player defined as
  subclasses of input system

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Types of part-whole relations

• Based on three distinctions
• Configurability
• Functional/structural relation with the other
  parts or the whole yes/no
• Homeomerous
• Parts are same kind as the whole yes/no
• Invariance
• Parts can be separated from the whole

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Component-integral

• Functional/structural relation to the whole
• Parts can be removed and are different from whole
• Organization of the parts
• Examples car wheels, film scenes
• N.B. difference between wheel and car wheel

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Material-object

• Invariant configuration
• Examples
• A bicycle is partly iron
• Wine is partly alcohol
• Human body is partly water
• The made-off relation
• Relation between part and whole is not known

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Portion-object

• Homeomeric configuration of parts
• Examples
• A lice of bread is part of a loaf of bread
• A sip of coffee is part of a cup o coffee
• Portions can be quantified with standard measures
  (liter, gram, ..)
• Homeomeric a sip of coffee is coffee (but a
  bicycle wheel is not a bicycle)
• Ingredients of portion and object are the same

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Place-area

• Homeomeric invariant configuration
• Examples
• North-Holland is part of The Netherlands
• The Mont Blanc peak is part of the Mont Blanc
  mountain
• The head is part of the human body (?!)
• Typically between places and locations

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Member-bunch

• No configuration, no invariance, not homeomeric
• Members of a collection
• Examples
• A tree is part of a wood
• The hockey player is part of a club
• Differentiate from classification-based
  collections
• A tree is a member of the class of trees

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Member-partnership

• Same as member-bunch, but invariant
• If a part is removed, the whole ceases to exist
• Examples
• Bonny and Clyde
• Laurel and Hardy
• Two married people

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Confusion with non-compositional relations

• Temporal topological inclusion
• The customer is in the store, but not part of it
• Classification inclusion
• A Bond movie is an instance of film but part of
  my film collection
• Attribution
• The height and width of a ship are not part of
  the ship
• Attachment
• A wrist watch is not part of the wrist
• Ownership
• I own a bicycle but it is not part of me

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Transitivity of part-whole types

• Transitivity does not (necessarily) hold when
  traversing different types of part-whole relation
• I am a member of a club (member-bunch)
• My head is part of me (place-area)
• But my head is not a part of the club

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Characteristics of part-whole relations

• Vertical relationships
• Existence dependency between whole and part
• Feature dependencies
• Inheritance from part to whole defective
• Inheritance from whole to part owner
• Systematic relation weight whole sum weight
  parts
• Horizontal relationships
• Constraints between parts

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N-ary relations
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Pattern 1 dependent values

• Relation between two concept
• One of the concept can have multiple features
  that depend on the relation
• Example temperature of a person

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Pattern 1 example instance
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Pattern 1 class constraints
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Pattern 2 relation as class

• The relation itself is a concept
• All arguments are equally important
• Examples
• Enrollment
• Transaction
• Purchase
• See also the notion of UML association class

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Association class
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Pattern 2 example instance
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Pattern 2 class constraints
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Guidelines for choosing names

• Be as specific as possible
• Dont be afraid of long names
• Use a consistent syntax
• Capitalization
• Use of hyphens/spaces
• Do not worry yet about implementation!
• Classes nouns
• Operations verbs
• Associations attributes static or dynamic
  property

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Class-room exercise

• In certain combinations and minimum
  concentrations one or more amino acids can cause
  bitterness. Amino acids are divided into three
  groups Group I, II and III. Every amino acid has
  a unique chemical formula.

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Constructing subclass hierarchies
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Principles for backbone identification (Rector)

• Backbone should be a genuine tree
• Distinctions at one level of the subclass
  hierarchy should have he same decomposition
  principle (dimension)
• e.g. location
• Self-standing concepts
• Disjoint but open no exhaustive enumeration
  possible
• Partitioning/refining concepts
• Properties that carve up the subsumption space in
  exhaustive disjoint partitions

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Example backbone analysis

• Hormone
• Steroid hormone
• Cortisol
• Protein Hormone
• Insulin
• ATPase

• Substance
• Enzyme
• Protein
• Steroid
• Catalyst

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Backbone physical/chemical structure

• Substance
• Protein
• Insulin
• ATPase
• Steroid
• Cortisol

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Roles non-primitive types

• PhysiologicalRole
• HormoneRole
• CatalystRole
• Hormone Substance AND
• playsRole HormoneRole
• Enzyme Protein AND
• playsRole CatalystRole
• Insulin gt playsRole HormoneRole

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OntoClean

• Guarino Welty,
• Method for rationalizing subclass hierarchies
• Metaproperties for characterizing classes
• Rigidity
• Identity
• Unity
• Are used to analyze an existing subsumption
  hierarchy

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Rigid class properties

• Are essential for all its instances
• It must always hold, and not just accidentally
• Semi-rigid essential for some of the instances
• Anti-rigid not essential for all instances
• Anti-rigid properties cannot be superclasses of
  rigid properties

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Example of applying rigidity

• Class Human
• hasBodyWeight (rigid)
• isFather (anti-rigid)
• isFemale (non-rigid)

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Identity

• Refers to the problem of being able to recognize
  objects of a certain class
• Identity criteria
• How do we recognize an object as belonging to a
  class?
• Should hold over time
• How can one determine two instances are the same
  or different?
• Identity criteria are inherited over the
  subsumption relation

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Example of identity criteria

• Class Human
• Different bodies
• Class Article
• Citation information
• Class GeographicalLocation
• Latitude/longitude coordinates

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Example of use of Identity

• Does the class TimeDuration (e.g. 1 hour)
  subsume the class TimeInterval (e.g. 1100-1200
  today)?
• Check identity multiple instances of
  TimeInterval can be identified as the same
  instance of TimeDuration
• Compare this to the subsumption relation between
  Human and Female

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Unity

• How to determine something is a whole?
• How to determine which are the parts?
• Unit criteria
• Criteria for essential parts
• Criteria for conditions between the parts
• Guideline for analyzing subsumption hierarchies
• Wholes should not be subclasses of non-wholes

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Examples of unity

• Is water a unity?
• Not if it has no clear boundaries
• But the following are unities
• An ocean
• A cup of water
• Applying the guideline
• Can water be a superclass of ocean?

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Ontological analysis of a subsumption hierarchy

• Identifying the backbone
• Subclasses based on rigid properties
• Can also help in comparing two hierarchies
• Discovering inconsistencies in hierarchies
• List of common types of misuse of subsumption

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Misuse of subsumptioninstantiation

• Some cases are easy
• Asia in not a subclass of Continent, but an
  instance
• BillClinton is not a subclass of Human, but an
  instance of it.
• Consider the subclass hierarchy
• Animal ? Mammal ? Human
• What is the relation between Species and Human?

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Modelling issueclasses as instances
Aircraft no-of-seats positive integer owner
Airline Fokker-70 subclass of
Aircraft no-of-seats 60-80 PH-851 instance
of Fokker-70 no-of-seats 65 owner KLM

• Aircraft-type
• no-of-engines integer gt0
• propulsion propeller, jet
• Fokker-70
• instance of Aircraft-type
• no-of-engines 2
• propulsion jet

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Misuse of subsumptionpart-whole

• Common error
• E.g. Engine is not a subclass of Car
• See previous lecture

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Type restriction

• Is CarPart a superclass of Engine?
• No, there are engines which are not car parts
• Engine has rigid properties
• Car parts have no rigid properties
• gt CarPart cannot subsume Engine

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Polysemy

• Example confusion
• This book is heavy
• I liked this book
• Using a term in two different senses
• Cf. concept/term debate in thesauri

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Example dirty hierarch
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Hierarchy after cleaning
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Summary

• Construction of subclass hierarchies is error
  prone
• Techniques for normalization through ontological
  analysis exist
• Main advantage of normalized hierarchy is ease of
  understanding by others
• Prevention of misunderstandings when hierarchy is
  shared

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More information