1. An Extended GHKM Algorithm for Inducing λ-SCFG Peng Li pengli09@gmail.com Tsinghua University

2. Semantic Parsing Mapping natural language (NL) sentence to its computable meaning representation (MR) NL: Every boy likes a star MR: variable predicate

3. Motivation Common way: inducing probabilistic grammar PCFG: Probabilistic Context Free Grammar

4. Motivation Common way: inducing probabilistic grammar CCG: Combinatory Categorial Grammar

5. Motivation Common way: inducing probabilistic grammar SCFG: Synchronous Context Free Grammar

6. Motivation State of the art: SCFG + λ-calculus (λ-SCFG) Major challenge: grammar induction – It is much harder to find the correspondence between NL sentence and MR than between NL sentences SCFG rule extraction is well-studied in MT GHKM is the most widely used algorithm We want to adapt GHKM to semantic parsing Experimental results show that we get the state- of-the-art performance

7. Background State of the art: SCFG + λ-calculus (λ-SCFG) λ-calculus – λ-expression: – β-conversion: bound variable substitution – α-conversion: bound variable renaming

8. λ-SCFG Rule Extraction Outline 1.Building training examples 1.Transforming logical forms to trees 2.Aligning trees with sentences 2.Identifying frontier nodes 3.Extracting minimal rules 4.Extracting composed rules

9. Building Training Examples NL: Every boy likes a star MR:

10. Building Training Examples

12. boy human pop like

13. Building Training Examples boy human pop like Every boy likes a star

14. Identifying Frontier Nodes

17. Identifying Minimal Frontier Tree

22. Minimal Rule Extraction X X

23. X X

24. X X

25. Composed Rule Extraction

26. λ-SCFG Rule Extraction Outline 1.Building training examples 1.Transforming logical forms to trees 2.Aligning trees with sentences 2.Identifying frontier nodes 3.Extracting minimal rules 4.Extracting composed rules

27. Modeling Log-linear model + MERT training Target

28. Parsing Type checking (Wong and Mooney, 2007)

29. Experiments Dataset: G EOQUERY – 880 English questions with corresponding Prolog logical form – Metric

30. Experiments SCFG PCFG CCG

31. Experiments F-measure for different languages * en - English, ge - German, el - Greek, th - Thai

32. Experiments

33. Experiments