Introduction to Ontologies

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Introduction to Ontologies
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Reusable Specifications as Ontologies

• An ontology is a partial specification of a
  conceptual vocabulary to be used for formulating
  knowledge-level theories about a domain of
  discourse. The fundamental role of an ontology
  is to support knowledge sharing and reuse.

Example Ontology Simple-TimeDefines classes,
relations and axioms to support the modelling
of time-dependent activities
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Classes and Relations in Simple Time

• Classes
• Day-Name
• Day-Number
• Duration
• Hour-Number
• Minute-Number
• Month-Name
• Month-Number
• Second-Number
• Time-Point
• Calendar-Date
• Calendar-Year
• Universal-Time-Spec
• Time-Range
• Year-Number

• Relations
• lt
• gt
• After
• After
• Before
• Before
• Disjoint-Time-Ranges
• During
• During
• Equals
• Finishes
• Finishes
• Meets
• Overlaps
• Overlaps
• Start
• Starts

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Definition of Time Point

• (def-class TIME-POINT (time-position) "A point
  in time" ((second-of type second-in-time
  max-cardinality 1 ) (minute-of type
  minute-in-time max-cardinality 1 ) (hour-of
  type hour-in-time max-cardinality 1 )
  (day-of type day-in-time max-cardinality 1)
  (month-of type month-in-time max-cardinality
  1) (year-of type year-in-time
  max-cardinality 1 )) constraint (and
  (not (and (month-of ?x 2)
  (gt (the ?day
  (day-of ?x ?day))
  29))) (not (and (member-of ?x (4 6
  9 11)) (gt (the ?day
  (day-of ?x ?day))
  30)))))

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Ontology for medical guidelines

• What is a medical guideline?
• A specification (often partial) of a protocol of
  care
• Aims to define best practice
• Examples
• Protocols for treating AIDS patients
• Protocols for the prevention of bed sores
• The Ontology
• Defines classes, relations and axioms to support
  the specification of medical guidelines
• Builds on a generic medical ontology
• Supports both guideline design and execution.

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Advantages of Ontologies (1) Reuse
base-ontology
simple-time
common-concepts
generic-events
bibliographic-data
generic-technologies
organization-ontology
medical-ontology
medical-guidelines
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Class Hierarchy for Medical Guidelines
Simple-time Ontology
Temporal-thing
Common Concepts Ontology
Plan
Medical-Guidelines Ontology
Medical-Guideline
Therapeutic-Guideline
Preventive-Guideline
Diagnostic-Guideline
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Advantages of Ontologies (2)

• Formal Community View
• Make it possible to formalise a shared viewpoint
  over a certain universe of discourse
• E.g., agreement on how to model time
• Interoperability
• Can support communication and cooperation between
  systems developed at different sites
• The ontological commitments made by a system are
  made explicit
• E.g., diagnostic and therapy-control medical
  systems may share the same underlying generic
  medical ontology
• e.,g., notion of pathological state, therapeutic
  procedure

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Advantages of Ontologies (3)

• Model-based knowledge acquisition
• E.g., use the medical guideline ontology to
  acquire knowledge about particular medical
  guidelines in a structured way
• Knowledge-level validation and verification
• E.g., use the medical guideline ontology to check
  guideline documents

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Criteria for Ontology Design

• Clarity
• User-centred definitions
• Documentation
• Alternative choices
• Coherence
• Logical consistency
• Coherent Style (e.g., naming conventions)
• Minimal ontological commitments
• Do not impede extensibility by making unnecessary
  knowledge-level commitments
• Minimal encoding bias
• Do not pre-judge reuse by making symbol-level
  commitments

(Gruber, 1995)
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Example of not-so-good definition
Physical Quantity ltUnit, Magnitudegt Example
ltsecond, 5gt

• (defrelation PHYSICAL-QUANTITY
• (ltgt (PHYSICAL-QUANTITY ?q)
• (and (defined (quantity.magnitude
  ?q))
• (double-float
  (quantity.magnitude ?q))
• (defined (quantity.unit
  ?q))
• (member (quantity.unit ?q)
• (setof
  meter second kilogram
  ampere kelvin mole
  candela)))

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Example of not-so-good definition
Physical Quantity ltUnit, Magnitudegt Example
ltsecond, 5gt

• (defrelation PHYSICAL-QUANTITY
• (ltgt (PHYSICAL-QUANTITY ?q)
• (and (defined (quantity.magnitude
  ?q))
• (double-float
  (quantity.magnitude ?q))
• (defined (quantity.unit
  ?q))
• (member (quantity.unit ?q)
• (setof
  meter second kilogram
  ampere kelvin mole
  candela)))

Encoding Bias
Unnecessary Ontological Commitment
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AKT Reference Ontology

• Task Develop a common ontology to describe
  academic resources
• Rationale
• Ontology to provide a common semantic basis to
  support variety of AKT services
• Gather data about collaborative development
• Test tools
• Take Integration and Collaboration seriously

AKT is a 6-year UK 11M focusing on knowledge
technologies, involving 5 universities
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Organization of AKT Reference Ontology

• 100 self-contained
• Two-subontologies
• AKT-Support
• Frames, Sets, Numbers, Lists, Relations, Time,
  Micro Top Level
• AKTive-Portal
• Technologies, Events, People Organizations,
  Documents, Research Areas and Projects

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Publishing through D3E
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Setup for collaborative ontology design
Screen 1OntologyBrowsers
Screen 2Discussion/RationaleCapture in
Compendium
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Publishing through D3E
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Typology of Comments
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AKT-2 Architecture
Southampton
RDF
OKBC Triple Store
RDF
Edinburgh.
RDF
AKT Reference Ontology
Aberdeen.
RDF
RDF
Sheffield.
E-print server
Amilcare
RDF
OU
News server
Wilbur
AKT Portal Client
Freaky
OCML
OCML
AKT Reference Ontology
AKT Portal KB
Aktive Portal Server
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Exercise Analysis of AKT Reference Ontology
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Class Medical-Guideline

• (def-class medical-guideline (plan)
• "Each guideline is associated with a medical
• condition. It also targets a particular
  population"
• ((outcome-measure type string)
• (target-population type population-specificati
  on)
• (full-name type string)
• (associated-medical-condition type
  medical-condition)
• (temporal-constraints type string)
• (location-constraints
• type guideline-application-location)
• (associated-documents type document-reference)
  
• (has-guideline-user-type type
  guideline-user-type)))