Constituency Parsing Data structures and algorithms for Computational Linguistics III Çağrı Çöltekin ccoltekin@sfs.uni-tuebingen.de University of Tübingen Seminar für Sprachwissenschaft Winter Semester 2019–2020
Introduction CKY WS 19–20 SfS / University of Tübingen Ç. Çöltekin, sequence of terminal or non-terminal symbols parsing CF languages recap natural language syntax Context free grammars Summary Earley 1 / 29 • Context free grammars are suffjcient for expressing most phenomena in • Most of the parsing theory (and quite some of the practice) is build on • The context-free rules have the form A → α where A is a single non-terminal symbol and α is a (possibly empty)
Introduction VP Derivation of sentence ‘she saw a duck’ S V N S NP Prn she V V saw NP Det a N duck Ç. Çöltekin, SfS / University of Tübingen WS 19–20 CKY 2 / 29 V N Earley Summary An example context-free grammar S V S N → NP VP → Aux NP VP ⇒ NP VP NP → Det N NP ⇒ Prn NP → Prn Prn ⇒ she NP → NP PP VP → V NP VP ⇒ V NP VP → V ⇒ saw VP → VP PP NP ⇒ Det N PP → Prp NP Det ⇒ a → duck ⇒ duck → park → duck → ducks → saw Prn → she | her Prp → in | with Det → a | the
Introduction Prn p WS 19–20 SfS / University of Tübingen Ç. Çöltekin, NP S A sequence with (labeled) brackets CKY A history of derivations: duck N her 3 / 29 NP NP Earley Summary Representations of a context-free parse tree A parse tree: saw S Prn V VP I • S ⇒ NP VP • NP ⇒ Prn • Prn ⇒ I • VP ⇒ V NP • V ⇒ saw • NP ⇒ Prn p N • Prn p ⇒ her • N ⇒ duck [ ]]] [ ][ [ [ ] NP [ Prn I ] VP [ V saw ] [ N duck ] Prn p her
Introduction CKY Earley Summary Parsing as search Ç. Çöltekin, SfS / University of Tübingen WS 19–20 4 / 29 • Parsing can be seen as search constrained by the grammar and the input • Top down: start from S , fjnd the derivations that lead to the sentence • Bottom up: start from the sentence, fjnd series of derivations (in reverse) that leads to S • Search can be depth fjrst or breadth fjrst for both cases
Introduction N saw a duck Backtrack! S CKY N duck V V V Ç. Çöltekin, SfS / University of Tübingen WS 19–20 she S N a Earley Summary Parsing as search: top down S NP Det Prn she 5 / 29 N Det NP saw V VP → NP VP → Aux NP VP NP → Det N NP → Prn NP → NP PP VP → V NP VP → V VP → VP PP PP → Prp NP → duck → park → duck → ducks → saw Prn → she | her Prp → in | with Det → a | the
Introduction N saw a duck Backtrack! S CKY N duck V V V Ç. Çöltekin, SfS / University of Tübingen WS 19–20 she S N a Earley Summary Parsing as search: top down S NP Det Prn she 5 / 29 N Det NP saw V VP → NP VP → Aux NP VP NP → Det N NP → Prn NP → NP PP VP → V NP VP → V VP → VP PP PP → Prp NP → duck → park → duck → ducks → saw Prn → she | her Prp → in | with Det → a | the
Introduction N saw a duck Backtrack! S CKY N duck V V V Ç. Çöltekin, SfS / University of Tübingen WS 19–20 she S N a Earley Summary Parsing as search: top down S NP Det Prn she 5 / 29 N Det NP saw V VP → NP VP → Aux NP VP NP → Det N NP → Prn NP → NP PP VP → V NP VP → V VP → VP PP PP → Prp NP → duck → park → duck → ducks → saw Prn → she | her Prp → in | with Det → a | the
Introduction N saw a duck Backtrack! S CKY N duck V V V Ç. Çöltekin, SfS / University of Tübingen WS 19–20 she S N a Earley Summary Parsing as search: top down S NP Det Prn she 5 / 29 N Det NP saw V VP → NP VP → Aux NP VP NP → Det N NP → Prn NP → NP PP VP → V NP VP → V VP → VP PP PP → Prp NP → duck → park → duck → ducks → saw Prn → she | her Prp → in | with Det → a | the
Introduction N saw a duck Backtrack! S CKY N duck V V V Ç. Çöltekin, SfS / University of Tübingen WS 19–20 she S N a Earley Summary Parsing as search: top down S NP Det Prn she 5 / 29 N Det NP saw V VP → NP VP → Aux NP VP NP → Det N NP → Prn NP → NP PP VP → V NP VP → V VP → VP PP PP → Prp NP → duck → park → duck → ducks → saw Prn → she | her Prp → in | with Det → a | the
Introduction N saw a duck Backtrack! S CKY N duck V V V Ç. Çöltekin, SfS / University of Tübingen WS 19–20 she S N a Earley Summary Parsing as search: top down S NP Det Prn she 5 / 29 N Det NP saw V VP → NP VP → Aux NP VP NP → Det N NP → Prn NP → NP PP VP → V NP VP → V VP → VP PP PP → Prp NP → duck → park → duck → ducks → saw Prn → she | her Prp → in | with Det → a | the
Introduction N saw a duck Backtrack! S CKY N duck V V V Ç. Çöltekin, SfS / University of Tübingen WS 19–20 she S N a Earley Summary Parsing as search: top down S NP Det Prn she 5 / 29 N Det NP saw V VP → NP VP → Aux NP VP NP → Det N NP → Prn NP → NP PP VP → V NP VP → V VP → VP PP PP → Prp NP → duck → park → duck → ducks → saw Prn → she | her Prp → in | with Det → a | the
Introduction N saw a duck Backtrack! S CKY N duck V V V Ç. Çöltekin, SfS / University of Tübingen WS 19–20 she S N a Earley Summary Parsing as search: top down S NP Det Prn she 5 / 29 N Det NP saw V VP → NP VP → Aux NP VP NP → Det N NP → Prn NP → NP PP VP → V NP VP → V VP → VP PP PP → Prp NP → duck → park → duck → ducks → saw Prn → she | her Prp → in | with Det → a | the
Introduction N saw a duck Backtrack! S CKY N duck V V V Ç. Çöltekin, SfS / University of Tübingen WS 19–20 she S N a Earley Summary Parsing as search: top down S NP Det Prn she 5 / 29 N Det NP saw V VP → NP VP → Aux NP VP NP → Det N NP → Prn NP → NP PP VP → V NP VP → V VP → VP PP PP → Prp NP → duck → park → duck → ducks → saw Prn → she | her Prp → in | with Det → a | the
Introduction N saw a duck Backtrack! S CKY N duck V V V Ç. Çöltekin, SfS / University of Tübingen WS 19–20 she S N a Earley Summary Parsing as search: top down S NP Det Prn she 5 / 29 N Det NP saw V VP → NP VP → Aux NP VP NP → Det N NP → Prn NP → NP PP VP → V NP VP → V VP → VP PP PP → Prp NP → duck → park → duck → ducks → saw Prn → she | her Prp → in | with Det → a | the
Introduction N saw a duck Backtrack! S CKY N duck V V V Ç. Çöltekin, SfS / University of Tübingen WS 19–20 she S N a Earley Summary Parsing as search: top down S NP Det Prn she 5 / 29 N Det NP saw V VP → NP VP → Aux NP VP NP → Det N NP → Prn NP → NP PP VP → V NP VP → V VP → VP PP PP → Prp NP → duck → park → duck → ducks → saw Prn → she | her Prp → in | with Det → a | the
Introduction VP WS 19–20 SfS / University of Tübingen Ç. Çöltekin, V V V N N CKY S S S 6 / 29 NP Prn Earley Summary Parsing as search: bottom up she saw a NP duck Det N V → NP VP → Aux NP VP NP → Det N NP → Prn NP → NP PP VP → V NP VP → V VP → VP PP PP → Prp NP → duck → park → duck → ducks → saw Prn → she | her Prp → in | with Det → a | the
Introduction VP WS 19–20 SfS / University of Tübingen Ç. Çöltekin, V V V N N CKY S S S 6 / 29 NP Prn Earley Summary Parsing as search: bottom up she saw a NP duck Det N V → NP VP → Aux NP VP NP → Det N NP → Prn NP → NP PP VP → V NP VP → V VP → VP PP PP → Prp NP → duck → park → duck → ducks → saw Prn → she | her Prp → in | with Det → a | the
Introduction VP WS 19–20 SfS / University of Tübingen Ç. Çöltekin, V V V N N CKY S S S 6 / 29 NP Prn Earley Summary Parsing as search: bottom up she saw a NP duck Det N V → NP VP → Aux NP VP NP → Det N NP → Prn NP → NP PP VP → V NP VP → V VP → VP PP PP → Prp NP → duck → park → duck → ducks → saw Prn → she | her Prp → in | with Det → a | the
Introduction VP WS 19–20 SfS / University of Tübingen Ç. Çöltekin, V V V N N CKY S S S 6 / 29 NP Prn Earley Summary Parsing as search: bottom up she saw a NP duck Det N V → NP VP → Aux NP VP NP → Det N NP → Prn NP → NP PP VP → V NP VP → V VP → VP PP PP → Prp NP → duck → park → duck → ducks → saw Prn → she | her Prp → in | with Det → a | the
Introduction VP WS 19–20 SfS / University of Tübingen Ç. Çöltekin, V V V N N CKY S S S 6 / 29 NP Prn Earley Summary Parsing as search: bottom up she saw a NP duck Det N V → NP VP → Aux NP VP NP → Det N NP → Prn NP → NP PP VP → V NP VP → V VP → VP PP PP → Prp NP → duck → park → duck → ducks → saw Prn → she | her Prp → in | with Det → a | the
Introduction VP WS 19–20 SfS / University of Tübingen Ç. Çöltekin, V V V N N CKY S S S 6 / 29 NP Prn Earley Summary Parsing as search: bottom up she saw a NP duck Det N V → NP VP → Aux NP VP NP → Det N NP → Prn NP → NP PP VP → V NP VP → V VP → VP PP PP → Prp NP → duck → park → duck → ducks → saw Prn → she | her Prp → in | with Det → a | the
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