Issues and Conclusion.

1
Issues and Conclusion.
2
Ontology Bottlenecks

• Where do they come from
• How do you keep them up to date
• What about when they change
• Multiple ontologies
• How do you link them to the services

3
Basic Ontological IssuesCommon Bear Traps

• Formalism restricts what can be said
• Dont torture it e.g. no negation no shared
  variables
• Semantic Redundancy
• More than one way to say ? equivalence
• Risk for links as well as concepts
• hasColour vs hasFeature Colour hasState
• Ambiguity
• Default Reasoning
• Birds fly, except penguins, ostriches and Dodos
• Partonomy and transitivity
• Spatial reasoning

4
Basic Ontological Issues Common Bear Traps

• Structure vs Process
• Ulcer vs Ulceration
• Substance vs Structure
• Glucose (mass weight, chemical structure)
• Changed state vs Change in state
• Increased vs Increasing
• Selectors
• Left hand left not actually a spatial
  signifier
• Numbers, ranges
• Concrete domains

5
Advanced Ontological IssuesMaintenance

• Maintenance
• Large ontology necessarily collaborative
  undertaking
• Need way to make editing task comprehensible (and
  shareable)
• Multiuser environments, coupling strategies
• Source sharing, organisation, training
• Performance and Scaling
• What can be done depends on how long an
  interation / experiment requires
• Working Method
• Iterate, test, iterate, test, iterate, test

6
Advanced Ontological IssuesDelivery

• Philosophical perfection does not guarantee
  utility
• Inevitably complex
• But useless if too confusing
• How to systematically simplify / guide ?
• Contrains what you do
• Think about delivery and your user
• How to make it look familiar ?
• Need for navigational hierarchies

7
Coding Confusion An example
Suitcase Luggage Attache case Model
Person Woman Adults Headcloth Cloth Scarf Standing
Background Brown Blue Chemise Dress Tunics Clothe
s Brass Instrument French Horn Horn Tuba
X X X X X
X X X X X X X
X X X X X X X
X X X X X X X X X X
X X X
X X X X X X
X X X X X X
X X X X X X
8

• Fuzziness

9
Inter-ontological relationships

• Synonyms
• leads to semantics preserving translations
• Hyponyms/Hypernyms
• lead to semantics altering translations
• typically results in loss of recall and precision
• List of Hyponyms
• technical-manual hyponym manual
• book hyponym book
• proceedings hyponym book
• thesis hyponym book
• misc-publication hyponym book
• technical-reports hyponym book
• press hyponym periodical-publicatio
  n
• periodical hyponym periodical-publicatio
  n

10
Ontology Integration and Query
Rewriting
union(Journal, union(Book, Proceedings, ...,
Misc-Publication)), union(Periodical-Publication,
union(Book, ....., Misc-Publication)),
Document
Journal, Periodical-Publication
union(Book, Proceedings, ..., Misc-Publication)
Technical-Manual
GuideBook
11

• The technical advantages of knowledge modeling
  are obvious. Knowledge bases can be automatically
  checked for consistency they support inference
  mechanisms which derive data which have not been
  explicitly stored they also offer extensive
  request and navigation facilities. However, the
  most immediate benefit of knowledge base design
  lies in the modeling process itself, through the
  effort of explication, organization and
  structuration sic of the knowledge it
  requires.
• Editorial Bioinformatics, July 2000

12

• How much do they cost?
• Lots.