The Descent of Hierarchy, and Selection in Relational Semantics*

1. The Descent of Hierarchy, and Selection in RelationalSemantics* Barbara Rosario, Marti Hearst, Charles Fillmore UC Berkeley *with apologies to Charles Darwin

2. Noun Compounds (NCs) • Technical text is rich with NCs Open-labeled long-term study of the subcutaneous sumatriptan efficacy and tolerability in acute migraine treatment. • Any sequence of nouns that itself functions as a noun • asthma hospitalizations • health care personnel hand wash

3. NCs: 3 computational tasks • Identification • Syntactic analysis (attachments) • [Baseline [headachefrequency]] • [[Tensionheadache] patient] • Our Goal: Semantic analysis • Headache treatment treatment forheadache • Corticosteroid treatment treatment that uses corticosteroid

4. Descent of Hierarchy • Idea: • Use the top levels of a lexical hierarchy to identify semantic relations • Hypothesis: • A particular semantic relation holds between all 2-word NCs that can be categorized by a lexical category pair.

5. Outline • Related work • Linguistic motivation • Lexical Hierarchy: MeSH • Labeling NC relations • Method and results • Discussion of ambiguity

6. Related work(Semantic analysis of NCs) • Rule-based • Finin (1980) • Detailed AI analysis, hand-coded • Vanderwende (1994) • automatically extracts semantic information from an on-line dictionary, manipulates a set of handwritten rules. 13 classes, 52% accuracy • Probabilistic • Lauer (1995): • probabilistic model, 8 classes, 47% accuracy • Lapata (2000) • classifies nominalizations into subject/object. 2 classes, 80% accuracy

7. Related work(Semantic analysis of NCs) • Lexical Hierarchy • Barrett et al. (2001) • WordNet, heuristics to classify a NC given the similarity to a known NC • Rosario and Hearst (2001) • MeSH, Neural Network. 18 classes, 60% accuracy • Relations pre-defined

8. Linguistic Motivation • Semantics of the NCs: head-modifier relationship • Head noun has argument structure • Meaning of the head noun determines what kinds of things can be done to it, what it is made of, what it is a part of…

9. Linguistic Motivation (cont.) • Material + Cutlery  Made of • steel knife, plastic fork, wooden spoon • Food + Cutlery  Used on • meat knife, dessert spoon, salad fork • Profession + Cutlery  Used by • chef's knife, butcher's knife

10. Outline • Related work • Linguistic motivation • Lexical Hierarchy: MeSH • Labeling NC relations • Method and results • Discussion of ambiguity

11. The lexical Hierarchy: MeSH Tree Structures 1. Anatomy [A] 2. Organisms [B] 3. Diseases [C] 4. Chemicals and Drugs [D] 5. Analytical, Diagnostic and Therapeutic Techniques and Equipment [E] 6. Psychiatry and Psychology [F] 7. Biological Sciences [G] 8. Physical Sciences [H] 9. Anthropology, Education, Sociology and Social Phenomena [I] 10. Technology and Food and Beverages [J] 11. Humanities [K] 12. Information Science [L] 13. Persons [M] 14. Health Care [N] 15. Geographic Locations [Z]

12. The lexical Hierarchy: MeSH 1. Anatomy [A]Body Regions [A01] 2. [B] Musculoskeletal System [A02] 3. [C] Digestive System [A03] 4. [D] Respiratory System [A04] 5. [E] Urogenital System [A05] 6. [F] …… 7. [G] 8. Physical Sciences [H] 9. [I] 10. [J] 11. [K] 12. [L] 13. [M]

13. Descending the Hierarchy 1. Anatomy [A]Body Regions [A01] Abdomen [A01.047] 2. [B] Musculoskeletal System [A02] Back [A01.176] 3. [C] Digestive System [A03] Breast [A01.236] 4. [D] Respiratory System [A04] Extremities [A01.378] 5. [E] Urogenital System [A05] Head [A01.456] 6. [F] …… Neck [A01.598] 7. [G] …. 8. Physical Sciences [H] 9. [I] 10. [J] 11. [K] 12. [L] 13. [M]

14. Descending the Hierarchy 1. Anatomy [A]Body Regions [A01] Abdomen [A01.047] 2. [B] Musculoskeletal System [A02] Back [A01.176] 3. [C] Digestive System [A03] Breast [A01.236] 4. [D] Respiratory System [A04] Extremities [A01.378] 5. [E] Urogenital System [A05] Head [A01.456] 6. [F] …… Neck [A01.598] 7. [G] …. 8. Physical Sciences [H] Electronics 9. [I] Astronomy 10. [J] Nature 11. [K] Time 12. [L] Weights and Measures 13. [M] ….

15. Descending the Hierarchy 1. Anatomy [A]Body Regions [A01] Abdomen [A01.047] 2. [B] Musculoskeletal System [A02] Back [A01.176] 3. [C] Digestive System [A03] Breast [A01.236] 4. [D] Respiratory System [A04] Extremities [A01.378] 5. [E] Urogenital System [A05] Head [A01.456] 6. [F] …… Neck [A01.598] 7. [G] …. 8. Physical Sciences [H] Electronics Amplifiers 9. [I] Astronomy Electronics, Medical 10. [J] Nature Transducers 11. [K] Time 12. [L] Weights and Measures 13. [M] ….

16. Descending the Hierarchy 1. Anatomy [A]Body Regions [A01] Abdomen [A01.047] 2. [B] Musculoskeletal System [A02] Back [A01.176] 3. [C] Digestive System [A03] Breast [A01.236] 4. [D] Respiratory System [A04] Extremities [A01.378] 5. [E] Urogenital System [A05] Head [A01.456] 6. [F] …… Neck [A01.598] 7. [G] …. 8. Physical Sciences [H] Electronics Amplifiers 9. [I] Astronomy Electronics, Medical 10. [J] Nature Transducers 11. [K] Time 12. [L] Weights and Measures Calibration 13. [M] ….Metric System Reference Standard

17. Descending the Hierarchy 1. Anatomy [A]Body Regions [A01]Abdomen [A01.047] 2. [B] Musculoskeletal System [A02]Back [A01.176] 3. [C] Digestive System [A03]Breast [A01.236] 4. [D] Respiratory System [A04]Extremities [A01.378] 5. [E] Urogenital System [A05]Head [A01.456] 6. [F] …… Neck [A01.598] 7. [G] …. 8. Physical Sciences [H] ElectronicsAmplifiers 9. [I] AstronomyElectronics, Medical 10. [J] NatureTransducers 11. [K] Time 12. [L] Weights and Measures Calibration 13. [M] ….Metric System Reference Standard Homogeneous Heterogeneous

18. Mapping Nouns to MeSH Concepts • headache recurrence C23.888.592.612.441 C23.550.291.937 • headache pain C23.888.592.612.441 G11.561.796.444 • breast cancer cells A01.236 C04 A11

19. Levels of Description headache pain • Level 0: C.23 G.11 • Level 1: C23.888 G11.561 • Level 1: C23.888.592 G11.561.796 • … • Original: C23.888.592.612.441 G11.561.796.444

20. Outline • Related work • Linguistic motivation • Lexical Hierarchy: MeSH • Labeling NC relations • Method and results • Discussion of ambiguity

21. Descent of Hierarchy • Idea: • Words falling in homogeneous MeSH subhierarchies behave “similarly” with respect to relation assignment • Hypothesis: • A particular semantic relation holds between all 2-word NCs that can be categorized by a MeSH category pairs

22. Grouping the NCs • CP: A02 C04 (Musculoskeletal System, Neoplasms) • skull tumors, bone cysts, bone metastases, skull osteosarcoma… • CP: C04 M01 (Neoplasms, Person) • leukemia survivor, lymphoma patients, cancer physician, cancer nurses…

23. Distribution of Category Pairs

24. Collection • ~70,000 NCs extracted from titles and abstracts of Medline • 2,627 CPs at level 0 (with at least 10 unique NCs) • We analyzed • 250 CPs with Anatomy (A) • 21 CPs with Natural Science (H01) • 3 CPs with Neoplasm (C04) • This represents 10% of total CPs and 20% of total NCs

25. Classification Method • For each CP • Divide its NCs into “training-testing” sets • “Training”: inspect NCs by hand • Start from level 0 0 • While NCs are not all similar • descend one level of the hierarchy • Repeat until all NCs for that CP are similar

26. Using the CPs for classification • CP: A02 C04 (Musculoskeletal System, Neoplasms) • skull tumors, bone cysts, bone metastases, skull osteosarcoma

27. Using the CPs for classification • CP: A02 C04 (Musculoskeletal System, Neoplasms) • skull tumors, bone cysts, bone metastases, skull osteosarcoma • Similar NCs • All NCs under the CP A02 C04 have the same semantic relationship • Location of disease? Disease in Anatomy?

28. Using the CPs for classification • CP: A02 C04 (Musculoskeletal System, Neoplasms) • skull tumors, bone cysts, bone metastases, skull osteosarcoma • Similar NCs • All NCs under the CP A02 C04 have the same semantic relationship • Location of disease? Disease in Anatomy? • Add CP: A02 C04 to the list of classification decisions Classification decisions A02 C04

29. Using the CPs for classification • CP: B06 B06 (Plants, Plants) • eucalyptus trees, apple fruits, rice grains, potato plants Classification decisions A02 C04

30. Using the CPs for classification • CP: B06 B06 (Plants, Plants) • eucalyptus trees, apple fruits, rice grains, potato plants • Similar • Same relationship • Add CP B06 B06 Classification decisions A02 C04 B06 B06

31. Using the CPs for classification • CP: C04 M01 (Neoplasms, Person) • leukemia survivor, lymphoma patients, cancer physician, cancer nurses… • Person afflicted by Disease? Person who treat Disease? • Too different! • Second noun needs to be more specific: Descend one level for the second noun Person Classification decisions A02 C04 B06 B06

32. Classification decisions A02 C04 B06 B06 C04 M01  C04 M01.643 C04 M01.526 Using the CPs for classification • CP: C04 M01 (Neoplasm, Person) • leukemia survivor, lymphoma patients, cancer physician, cancer nurses…  Too different! • CP: C04 M01.643 (Neoplasms, Patients) • leukemia survivor, lymphoma patients • Person afflicted by Disease • CP: C04 M01.526 (Neoplasms, Occupational Groups) • cancer physician, cancer nurses… • Person who treat Disease • OK

33. Classification Decisions • A02 C04 • B06 B06 • C04 M01 • C04 M01.643 • C04 M01.526 • A01 H01 • A01 H01.770 • A01 H01.671 • A01 H01.671.538 • A01 H01.671.868 • A01 M01 • A01 M01.643 • A01 M01.526 • A01 M01.898

34. Classification Decisions + Relations (future work) • A02 C04  Location of Disease • B06 B06  Kind of Plants • C04 M01 • C04 M01.643  Person afflicted by Disease • C04 M01.526  Person who treats Disease • A01 H01 • A01 H01.770 • A01 H01.671 • A01 H01.671.538 • A01 H01.671.868 • A01 M01 • A01 M01.643 • A01 M01.526 • A01 M01.898

35. Classification Decisions + Relations (future work) • A02 C04  Location of Disease • B06 B06  Kind of Plants • C04 M01 • C04 M01.643  Person afflicted by Disease • C04 M01.526  Person who treats Disease • A01 H01 • A01 H01.770 • A01 H01.671 • A01 H01.671.538 • A01 H01.671.868 • A01 M01 • A01 M01.643  Person afflicted by Disease • A01 M01.526 • A01 M01.898

36. Classification Decision Levels • Anatomy: 250 CPs • 187 (75%) remain first level • 56 (22%) descend one level • 7 (3%) descend two levels • Natural Science (H01): 21 CPs • 1 (4%) remain first level • 8 (39%) descend one level • 12 (57%) descend two levels • Neoplasms (C04) 3 CPs: • 3 (100%) descend one level

37. Evaluation • Test the decisions on “testing” set • Count how many NCs that fall in the groups defined in the classification decisions are similar to each other • Accuracy: • Anatomy: 91% accurate • Natural Science: 79% • Neoplasm: 100% • Total Accuracy : 90.8% • Generalization: our 415 classification decisions cover ~ 46,000 possible CP pairs

38. Outline • Related work • Linguistic motivation • Lexical Hierarchy: MeSH • Labeling NC relations • Method and results • Discussion of ambiguity

39. Ambiguity – Two Types • Lexical ambiguity: • mortality • state of being mortal • death rate • Relationship ambiguity: • bacteria mortality • death of bacteria • death caused by bacteria

40. Lexical Ambiguity vs. Multiple MeSH Senses • Lexical ambiguity different from multiple MeSH senses • Ex: Mortality has 4 senses • Public Health (G)  Data Collection  Vital Statistics   Mortality • Investigative Techniques (E)  Data Collection  Vital Statistics   Mortality • Information Science (L)  Data Collection  Vital Statistics   Mortality • Population Characteristics (N)  Demography  Vital Statistics   Mortality • On average, there are 1.5 MeSH senses per word for the nouns in our collection

41. Four Cases Single MeSH senses Multiple MeSH senses Only one possible relationship: abdomen radiography, aciclovir treatment Only one possible relationship: alcoholism treatment Multiple relationships: hospital databases, education efforts, kidney metabolism Multiple relationships bacteria mortality Ambiguity of relationship

42. Four Cases Single MeSH senses Multiple MeSH senses Only one possible relationship: abdomen radiography, aciclovir treatment Only one possible relationship: alcoholism treatment Multiple relationships bacteria mortality Multiple relationships: hospital databases, education efforts, kidney metabolism Most problematic cases Ambiguity of relationship … but rare!

43. Conclusions • Very simple method for assigning semantic relations to two-word technical NCs • 90.8% accuracy • Grouping the NCs with respect to their semantic descriptors • Lexical resource (MeSH) useful for this task • Use the upper levels of the lexical hierarchy for an accurate classification, reducing therefore the space of the problem

44. Future work • Analyze full spectrum of hierarchy • NCs with > 2 terms • [[growth hormone] deficiency] • Other syntactic structures • Non-biomedical words • Other ontologies (e.g.,WordNet)?

45. And given enough data… • skull character • jaw depression • nose resuscitation • cadaver motion

46. Thanks!For more information:http://bailando.sims.berkeley.edu/lindi/