A Latent Variable Parser | Lexicalization has been shown to be useful in more general parsing applications due to lexical dependencies in constituent parsing (e.g. |
A Latent Variable Parser | However, topological fields explain a higher level of structure pertaining to clause-level word order, and we hypothesize that lexicalization is unlikely to be helpful. |
Experiments | We hypothesized earlier that lexicalization is unlikely to give us much improvement in performance, because topological fields work on a domain that is higher than that of lexical dependencies such as subcategorization frames. |
Experiments | However, given the locally independent nature of legitimate parentheticals, a limited form of lexicalization or some other form of stronger contextual information might be needed to improve identification performance. |
Introduction | In Dubey and Keller (2003), PCFG parsing of NEGRA is improved by using sister-head dependencies, which outperforms standard head lexicalization as well as an unlexicalized model. |
Building a Discourse Parser | EDUS Syntax Trees I Syntax Parsing (Charniak's n/parse) ' v I Tokenization l I Lexicalization l . |
Building a Discourse Parser | Lexicalized (SPADE) Tokenized EDUs Syntax Trees |
Building a Discourse Parser | Lexicalized Syntax Trees |
Experiments | Figure 4: Coverage of lexicalized STSG rules on bilingual phrases. |
Experiments | We extracted phrase pairs from the training data to investigate how many phrase pairs can be captured by lexicalized tree-to-tree rules that contain only terminals. |
Rule Extraction | If the tree contains only one node, it must be a lexicalized frontier node; |
Rule Extraction | If the tree contains more than one nodes, its leaves are either non-lexicalized frontier nodes or lexicalized non-frontier nodes. |
Abstract | By adding features over CCG word-word dependencies and lexicalized verbal subcategorization frames (“supertags”), we can obtain an F-score that is substantially better than a previous CCG-based SRL system and competitive with the current state of the art. |
Potential Advantages to using CCG | Another advantage of a CCG-based approach (and lexicalist approaches in general) is the ability to encode verb-specific argument mappings. |
Results | We argue that, especially in the heaVily lexicalized CCG framework, headword evaluation is more appropriate, reflecting the emphasis on headword combinatorics in the CCG formalism. |