1. Classification Grouping of like objects (entities, documents, products) Aboutness Collocation –Taxonomy, Ontology, Schema, Systematics, Nomenclature,….

2. Classification History Aristotle –Category (Greek kategoría, accusation, attribution). –E.g., Blood-bearing animals Four-footed animals, live birth Birds Egg-laying 4-footed animals (reptiles + amphibians) Whales and their allies Fishes Carl Von Linne, (Linnaeus)

3. Linnaean taxonomy

4. Classification History Aristotle - Classical Theory of Categories –things are categorized together based on what they have in common (properties) –Clear boundaries, hierarchy mirroring the actual world –Unchallenged until mid-19 th c.

5. Cracks in Classical Theory Research in logic and psychology –Wittgenstein, 1953, family resemblances –Austin, 1961, studied words –Zadeh, 1965, fuzzy set theory –Lonsbury, 1965, family kinship –Rosch, 1973-early 1980’s, prototype theory –Ad hoc categories

6. Human Categorization Anytime we see something as a kind of thing, for example, a tree, we are categorizing. Whenever we reason about kinds of things – chairs, nations, illnesses, emotions, any kind of things at all – we are employing categories. Lakoff, George (1987). Women, Fire, and Dangerous Things. Chicago, IL: University of Chicago Press.

7. Langridge Purpose –Facilitates everyday life –Choice of classification is always related to purpose Natural vs. Artificial classification –What is the difference? –Situational classification

8. Langridge Same object may be classified in many ways No absolute classification Classifications are made not discovered

9. Langridge Classification of phenomena not limited to sciences –Knowledge classification –Knowledge organization Is there a boundary? Bibliographic classification –Knowledge after it has been embodied –theme

11. Classification Used a multitude of places and environments: –Supermarkets –Knowledge bases of expert systems –Institutional archives & repositories –Digital & physical libraries (collocation and stack arrangement) –Web pages -- design of menus for interactive searching –Etc…

12. Classification Advantages Context, grouping Overview of the scope of a service Browsing, serendipity –Broadening and narrowing a search (hierarchy subject tree) –Browsing a directory-type structure is user friendly –Look for related items not previously identified as relevant - serendipity Partitioning / Segmenting (facets)

13. Classification Advantages continued Multilingual access –Same semantics across databases Interoperability on agreed classification schemes Permanence Known by users Available in machine readable form

14. Classification Criticisms Logical division splits related materials Illogical division of classes Difficulties and delay in adding new topics

15. BioMedical Classification systems 1. UMLS, MesH UMLSMesH 2. SNOMED CT SNOMED CT 3. LOINC LOINC 4. ICD ICD 5. GO GO 6. OBO Foundry OBO Foundry 7. Nation Center for Biomedical Ontology Nation Center for Biomedical Ontology

16. Structure of Classification Schemes Structure –Enumerative (a list) –Faceted (parts) –Hierarchical (structured from general to specific)

17. Enumerative History –Art history –Medieval history –Roman history –Scientific history –http://www.yahoo.comhttp://www.yahoo.com –http://www.froogle.comhttp://www.froogle.com

18. Faceted Faceted classification works on an “analytico-synthetic principle” –System: Fundamental concepts are analyzed and grouped together into facets –Concepts are combined or “synthesized” as necessary to form more complex subjects

19. Facets AAT (Art and Architecture Thesaurus) –Physical attributes (size, shape, texture) –Styles and periods –Agents –Materials –Objects (chair, painting) –http://www.getty.edu/research/conducting_researc h/vocabularies/aat/about.htmlhttp://www.getty.edu/research/conducting_researc h/vocabularies/aat/about.html Ornate style On-line Shopping (Best Buy)Best Buy

20. Hierarchical Super-ordinate and sub-ordinate Genus/species Class/member More flexible application in classification systems than in terminological tools (thesauri, ontologies, etc.) Example -- UMLS/MeSH

21. Hierarchical example w/BEER BEER Ale Bitter Brown Ale India Pale Ale Mild Pale Ale Lager Pilsner Porter Stout Sweet Stout Dry Stout Imperial Stout

22. MeSH Tree Browser Explore Mesh (use brain cancer) Mesh Tree Browser

23. What does the future hold Hint… Databases evolved from hierarchical to network, to relational. Maybe Classification is evolving from hierarchical to faceted (somewhat analogous to relational).