1. INFM 700: Session 6 Taxonomies and Metadata
Paul Jacobs
The iSchool
University of Maryland
Monday, October 26, 2009
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2. Today’s Topics Nature and types of metadata
General-purpose taxonomies (ontologies, thesauri, …)
Special-purpose taxonomies & thesauri
Practical use of taxonomies and metadata
Metadata
Taxonomies
& Thesauri
Practical Uses

3. Metadata Literally “data about data” Why do we need this?
“a set of data that describes and gives information about other data” ― Oxford English Dictionary
Why do we need this?
Types of metadata
Descriptive/subjective/content (e.g. author, subject, keywords, …)
Administrative (e.g. owner, rights, cost, creation date, version, …)
Technical (e.g. format, size, dependencies, programs)
In practical terms:
Metadata helps users locate, navigate, interpret content
Metadata helps organizations manage content
Metadata helps systems manipulate content
Metadata
Taxonomies
& Thesauri
Practical Uses

4. Data without Metadata…
Who:
authored it?
to contact about data?
What:
are contents of database?
When:
was it collected?
processed? finalized?
Where:
was the study done?
Why:
was the data collected?
How:
were data collected?
processed? Verified?
Metadata
Taxonomies
& Thesauri
Practical Uses
… can be pretty useless!

5. Early Example of Metadata
Taxonomies
& Thesauri
Practical Uses

6. Related Terms & Techniques
Taxonomies
Anything organized in some sort of hierarchical structure
Tagging
Adding almost any kind of metadata to content, but now often descriptive and user-provided
Thesauri
Focus on relations between terms
Focus on “concepts”
Ontologies
Usually model a specific domain or part of the world
Generally machine-readable
Metadata
Taxonomies
& Thesauri
Practical Uses
Increasing complexity and richness

7. Menagerie of Terms Classification Hierarchies Epistemology Directories
Controlled vocabularies
Knowledge representation
Metadata
Taxonomies
& Thesauri
Practical Uses
Let’s focus on significant differences.
Let’s focus on advantages/disadvantages.
Let’s focus on how each is useful.
Let’s not quibble over what to exactly call each.

8. Segue – Metadata to Taxonomies
What do taxonomies, thesauri, etc., have to do with meta-data?
Metadata
Taxonomies
& Thesauri
Practical Uses

9. Taxonomies Organization of objects according to some principle
Familiar examples:
Linnaean taxonomy (for living organisms)
Web directories (e.g., Yahoo or ODP)
Corporate directories
Organization charts
Organizational structures previously discussed
Metadata
Taxonomies
& Thesauri
Practical Uses

10. Thesauri: Motivation “Semantic gap” between concepts and words
Words are used to evoke concepts
Concrete objects: MacBook Pro, iPhone
Abstract ideas: freedom, peace
Concepts
Ideas
Words
Meaning
Metadata
Taxonomies
& Thesauri
Practical Uses

11. Words and concepts The semantic gap: What’s the problem?
Synonymy – roughly, different words or phrases can be used to express similar ideas (e.g. “notebook”, “laptop”)
Polysemy – roughly, the same word can have different meanings (e.g., “line” (fishing, code, queue, . . .) )
Taxonomies try to group similar concepts
“Tags” often assign words to concepts, making it easier to find related concepts
Controlled vocabularies avoid ambiguity (like a specific tag set)
Thesauri represent attempts to better organize mappings between words and concepts
Do these present precision or recall problems?
Metadata
Taxonomies
& Thesauri
Practical Uses

12. Some Real Examples
Content tagging and social media (e.g. flickr, del.i.cious)
Special-purpose classification schemes and thesauri (e.g. art & architecture thesaurus – AAT, UMLS)
General semantic tools and classification schemes (e.g., Princeton WordNet, Roget’s Thesaurus)
Metadata
Taxonomies
& Thesauri
Practical Uses

13. Think for a sec…
You are developing a content-rich site and need organization and labeling schemes to help users view/browse/learn/find stuff – what do you do?
Define your own tagging/organization scheme?
Let the users define their own?
Leave it all to a search engine?
Use some existing scheme?
. . .
Metadata
Taxonomies
& Thesauri
Practical Uses

14. Flickr – popular tags
Metadata
Taxonomies
& Thesauri
Practical Uses

15. Flickr – related tags
Metadata
Taxonomies
& Thesauri
Practical Uses

16. Del.icio.us – related tags
Metadata
Taxonomies
& Thesauri
Practical Uses

17. Art & Architecture Thesaurus
Metadata
Taxonomies
& Thesauri
Practical Uses

18. UMLS (Unified Medical Labeling System)
Source: National Library of Medicine (NIH)
SPECIALIST
Lexicon +Tools
Semantic
Network
Metathesaurus
135 broad categories and
54 relationships between them
lexical information and programs for language processing
1 million+
biomedical concepts from over 100 sources
Metadata
Taxonomies
& Thesauri
Practical Uses
3 Knowledge Sources
used separately or together

19. UMLS (Unified Medical Labeling System)
Source: National Library of Medicine (NIH)
Began in 1986 as long-term R&D project
Designed for systems developers
Develop multi-purpose tools to enhance understanding of medical meaning across systems
Overcome barriers to effective retrieval of machine-readable information
Overcome variety of ways the same concepts are expressed in machine readable and human language
Metadata
Taxonomies
& Thesauri
Practical Uses

20. UMLS Uses HIPAA, CHI, PHIN regulatory standards SNOMED CT
Source: National Library of Medicine (NIH)
Information retrieval
Thesaurus construction
Natural language processing
Automated indexing
Electronic health records (EHR)
Distribution mechanism for
HIPAA, CHI, PHIN regulatory standards
SNOMED CT
Metadata
Taxonomies
& Thesauri
Practical Uses

21. UMLS Metathesaurus http://www.nlm.nih.gov/research/umls/ Metadata
Taxonomies
& Thesauri
Practical Uses

22. UMLS Metathesaurus http://www.nlm.nih.gov/research/umls/ Metadata
Taxonomies
& Thesauri
Practical Uses

23. UMLS Thesaurus Browser
Metadata
Taxonomies
& Thesauri
Practical Uses

24. Think for a sec…
You are developing a content-rich site and need organization and labeling schemes to help users view/browse/learn/find stuff – what do you do?
Define your own tagging/organization scheme?
Let the users define their own?
Leave it all to a search engine?
Use some existing scheme?
. . .
Metadata
Taxonomies
& Thesauri
Practical Uses

25. Applying IA Principles
Focus on users and user needs – users are different, and have different models
Focus on content – concepts are different, too – different levels, words, complexity, vagueness
Examples:
What’s the difference between laptop, PDA, phone, and convergence device?
When is “cancer research” “oncology”?
When a user browses a furniture catalog for chairs, do you show them ottomans and footstools?
Metadata
Taxonomies
& Thesauri
Practical Uses

26. Standard Thesaurus Structure
Broader
Terms
Computer
IS-A
Preferred
Notebook
Laptop
Synonyms (variants)
AKA
IS-A
Metadata
Taxonomies
& Thesauri
Practical Uses
Narrower
Terms
Desktop Replacement
Ultraportable
Tablet PC

27. IA Uses of Thesauri For organization For navigation
For indexing content
For searching
Metadata
Taxonomies
& Thesauri
Practical Uses

28. Auschwitz II-Birkenau (Poland : Death Camp)
Poly-Hierarchies
Concepts can have multiple parents
Example:
Cracow (Poland : Voivodship)
German death camps
Auschwitz II-Birkenau (Poland : Death Camp)
Metadata
Taxonomies
& Thesauri
Practical Uses
Block 25 (Auschwitz II-Birkenau)
Kanada (Auschwitz II-Birkenau)
From Shoah Foundation’s thesaurus of holocaust terms

29. Poly-Hierarchies What are the advantages and disadvantages?
What’s the relationship to polysemy?
Metadata
Taxonomies
& Thesauri
Practical Uses

30. Practical Uses & Implementation
What are we trying to do (e.g., help users find stuff)?
What tools are at our disposal (e.g., tags, XML, databases)?
Given the above, how do we use/implement hierarchies and thesauri?
Metadata
Taxonomies
& Thesauri
Practical Uses

31. Faceted Hierarchies Alternative to single and poly-hierarchies
Basic idea:
Describe objects along multiple facets
Each facet has its associated hierarchy
Issues:
What’s a facet?
How do you navigate faceted hierarchies?
Metadata
Taxonomies
& Thesauri
Practical Uses

32. Faceted Browsing Example
Metadata
Taxonomies
& Thesauri
Practical Uses

33. Faceted Browsing Example
Metadata
Taxonomies
& Thesauri
Practical Uses

34. Faceted Browsing Example
Metadata
Taxonomies
& Thesauri
Practical Uses
Demo:

35. Advantages of Facets Integrates searching and browsing
Easy to build complex queries
Easy to narrow, broaden, shift focus
Helps users avoid getting lost
Helps to prevent “categorization wars”
Metadata
Taxonomies
& Thesauri
Practical Uses

36. Relationship to IA? Database Web Server Application Server
Network
Ontologies are implicitly “hidden” here!!!
Trip
Airplane
Type:
Capacity:
Part-of
Equipment
Flight
Metadata
Taxonomies
& Thesauri
Practical Uses
From:
Departure Time:
Origin:
To:
Arrival Time:
Destination:
Rule: Arrival Time is always after Departure Time
Rule: Distance from Origin to Destination typical > 100 miles

37. Putting it all together…
mySQL
Apache
Database
Web Server
PHP
Network
Two-Layer Architecture
Database
Web Server
Application Server
Network
Metadata
Taxonomies
& Thesauri
Practical Uses
Three-Layer Architecture

38. Popular Implementation
Presentation
PHP/HTML
Metadata
Taxonomies
& Thesauri
Practical Uses
Content
Metadata
SQL Database

39. Encoding Hierarchies Table: Hierarchy A Child Parent B A C D E F G H B
Store in RDBMS D E F G H
Metadata
Taxonomies
& Thesauri
Practical Uses
Finding children of A:
Select child from Hierarchy where parent = ‘A’  B, C
Finding parent of G:
Select parent from Hierarchy where child = ‘G’  D
Finding siblings of D:
find parent, and then find its children

40. Encoding Metadata Table: Items A ID Attributes … Label 0001 B 0002
0003 C
0004 D
0005
0006 E … B C D E F G H
Metadata
Taxonomies
& Thesauri
Practical Uses

41. Content  Presentation
You are here: A > C > D
Related
- D
- E B C
Contents at D D E F G H
Metadata
Taxonomies
& Thesauri
Practical Uses
Hierarchy(child, parent)
Content(id, attribute1, attribute2, attribute3, …)

42. Faceted Browsing Matching Results Filter by - Facet1 (possible values)
Metadata
Taxonomies
& Thesauri
Practical Uses
Hierarchy(child, parent)
Content(id, attribute1, attribute2, attribute3, …)

43. Recap Meta-data Taxonomies and Thesauri Practical use & implementation
General function
Types of meta-data
Taxonomies and Thesauri
Role in organizing, navigating and searching content
General-purpose taxonomies
Special-purpose taxonomies
Practical use & implementation
Metadata
Taxonomies
& Thesauri
Practical Uses