1 classification of semantic relations in noun compounds using mesh marti hearst, barbara rosario...
Post on 21-Dec-2015
224 Views
Preview:
TRANSCRIPT
1
Classification of Semantic Relations in Noun Compounds using MeSH
Marti Hearst, Barbara RosarioSIMS, UC Berkeley
2
LINDI Project Synopsis
Goal: Extract semantics from textMethod: statistical corpus analysisFocus: BioMedical text Interesting inferences (Swanson)Rich lexical resourcesDifficult NLP problems
Noun Compounds
3
Noun Compounds (NCs)
Any sequence of nouns that itself functions as a noun asthma hospitalizations asthma hospitalization rates bone marrow aspiration needle health care personnel hand wash
Technical text is rich with NCs Open-labeled long-term study of the subcutaneous sumatriptan efficacy and tolerability in acute migraine treatment.
4
NCs: 3 computational tasks
(Lauer & Dras ’94)IdentificationSyntactic analysis (attachments)
Baseline headache frequency Tension headache patient
Semantic analysis Headache treatment treatment for
headache Corticosteroid treatment treatment that uses
corticosteroid
[ ][ ][ ][ ]
5
NC Semantic Relations
Linguistic theories regarding the nature of the relations between constituents in NCs all conflict. J. Levi ‘78P. Downing ’77B. Warren ‘78
6
NC Semantic relations38 Relations found by iterative refinement based on 2245 NCsGoals:More specific than case rolesGeneral enough to aid coverageAllow for domain-specific relations
7
Semantic relationsExamples
Frequency/time of influenza season, headache interval
Measure of relief rate, asthma mortality, hospital survival
Instrument aciclovir therapy, laser irradiation, aerosol treatment
“Purpose” headache drugs, voice therapy, influenza treatment
Defect hormone deficiency, csf fistulas, gene mutation
Inhibitor Adrenoreceptor blockers, influenza prevention
8
Multi-class Assignment
Some NCs can be describe by more than one semantic relationships
eyelid abnormalities : location and defectfood allergy: cause and activator cell growth: change and activitytumor regression:change and
ending/reduction
9
Extraction of NCs
1. Titles and abstracts from Medline (medical bibliographic database)
2. Part of Speech Tagger3. Extraction of sequences of units
tagged as nouns4. Collection of 2245 NCs with 2
nouns
10
Models
Lexical (words) headache pain
Class based model using MeSH descriptors for levels of descriptions MeSH 2: C.23 G.11
MeSH 3: C23.888 G11.561
MeSH 4: C23.888.592 G11.561.796
MeSH 5: C23.888.592 G11.561.796
MeSH 6: C23.888.592.612 G11.561.796 .444
11
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
MeSH Tree Structures 1. Anatomy [A] Body Regions [A01] + Musculoskeletal System [A02] Digestive System [A03] + Respiratory System [A04] + Urogenital System [A05] + Endocrine System [A06] + Cardiovascular System [A07] + Nervous System [A08] + Sense Organs [A09] + Tissues [A10] + Cells [A11] + Fluids and Secretions [A12] + Animal Structures [A13] + Stomatognathic System [A14] (…..)
Body Regions [A01] Abdomen [A01.047]
Groin [A01.047.365] Inguinal Canal [A01.047.412] Peritoneum [A01.047.596] + Umbilicus [A01.047.849]
Axilla [A01.133] Back [A01.176] + Breast [A01.236] + Buttocks [A01.258] Extremities [A01.378] + Head [A01.456] + Neck [A01.598] (….)
13
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
14
Levels of Descriptionheadache pain (C23.888.592.612.441 G11.561.796.444)
Only Tree: C G C(Diseases) G (Biological Sciences)
Level 1 : C 23 G 11 C 23 (Diseases: Pathological Conditions) G 11 (Biological Sciences: Musculoskeletal, Neural, and Ocular Physiology)
Level 2 : C 23 888 G 11 561 C 23.888 (Diseases:Pathological Conditions: Signs and symptoms) G 11.561 (Biological Sciences: Musculoskeletal, Neural, and Ocular Physiology:Nervous
System Physiology)
Level 3 : C 23 888 592 G 11 561 796 C 23.888.592 (Diseases :Pathological Conditions: Signs and symptoms: Neurologic
Manifestations) G 11.561.796 (Biological Sciences: Musculoskeletal, Neural, and Ocular
Physiology:Nervous System Physiology:Sensation)
15
Classification Task & Method
Multi-class (18) classification problem
Multi layer Neural Networks to classify across all relations simultaneously.
Evaluation: distinguish between Seen: NCs where 1 or 2 words appeared in the
training set Unseen: NCs in which neither word appeared in
the training set
16
Accuracy for 18-way Classification
Training
855 NCs
(50%)
Testing:
805 NCs
(75 unseen)
Correct answer in first two (71%-73%)
Correct answer ranked first (61%-62%)
Correct answer in first three (76%-78%)
Baseline (guessing most frequent class)
Lexical
MeSH
17
Accuracies for 18-way classification: generalization on unseen NCs
Training:
73 NCs
(5%)
Testing:
1587 NCs
(810 unseen)
(95%)
MeSH
Lexical
MeSH on
unseen
Lexical on
unseen
18
Accuracies by Unseen Noun
Training:
73 NCs
(5%)
Testing:
1587 NCs
(810 unseen)
(95%)
Case 1: first N unseen
Case 2: second N unseen
Case 3: both N seen
Case 4: neither N seen
19
Accuracy for each relation
20
Accuracy for sample relations
Produces (genetic)
Ex. Test Set:thymidine alleletumor dna csf mrna acetylase gene virion rna (…)
21
Accuracy for sample relations
Frequency/time of
Test Set:disease recurrenceheadache recurrenceenterovirus seasoninfluenza seasonmosquito seasonpollen seasondisease stagetranscription stagedrive timeinjection timeischemia timetravel time
22
Accuracy for sample relations
Purpose
Test Set:varicella vaccine tb vaccines poliovirus vaccine influenza vaccinationinfluenza immunizationabscess drainage acne therapy asthma therapy asthma treatment carcinogen treatment disease treatment hiv treatment
23
Related work
Finin (1980) Detailed AI analysis, hand-coded
Rindflesch et al. (2000) Hand-coded rule base to extract certain
types of assertions
24
Related workVanderwende (1994) automatically extracts semantic information from an on-line
dictionary manipulates a set of handwritten rules 13 classes 52% accuracy
Lapata (2000) classifies nominalizations into subject/object binary distinction 80% accuracy
Lauer (1995): probabilistic model 8 classes 47% accuracy
25
Related workPrepositional Phrase Attachment The problem
Eat spaghetti with a fork Eat spaghetti with sauce V N1 P N2
Attachment/association, not semantics Approaches
Word occurrences (Hindle & Rooth ’93) Using a lexical hierarchy
Conceptual association (Resnik ’93, Resnik & Hearst ’93) Transformation-based (Brill & Resnik ’94) MDL to find optimal tree cut (Li & Abe ’98)
Lindi: use ML techniques to determine appropriate level of lexical hierarchy, classify into semantic relations
26
ConclusionsA simple method for assigning semantic relations to noun compounds Does not require complex hand-coded rules Does make use of existing lexical resources
High accuracy levels for an 18-way class assignment Small training set gets ~60% accuracy on
mixed seen and unseen words Tiny training set (73 NCs) gets ~40%
accuracy on entirely unseen words Off-the-shelf, unoptimized ML algorithms
27
Future work
Analysis of cases where it doesn’t workNC with > 2 termsHow to generalize patterns found for noun compounds to other syntactic structures? How can we best formally represent semantics?How can we deal with non medical words? Should we use other ontologies (e.g.,WordNet)?
28
Using Relations
Eventual plan: combine relations with constituents’ ontology membershipsExamples
Instrument_2 (biopsy,needle) -> Instrument_2(Diagnostic, Tool)
Procedure(brain,biopsy) -> Procedure(Anatomical-Element, Diagnostic)
Procedure(tumor, marker) -> Procedure(Disease-element, Indicator)
top related