Báo cáo khoa học: "Capturing CFLs with Tree Adjoining Grammars" potx

... referring to initial trees and auxiliary trees. A TAG derives trees by a sequence of substitutions and adjunctions in the elementary trees. In substitution an instance of an initial tree in which ... either an initial or auxiliary tree that is also labeled X. Both trees may be either an elementary tree or a derived tree. In adjunction an instance of an auxiliary tree in...

Ngày tải lên: 23/03/2014, 20:21

... non- terminals only increases by 1. Thus, simple context-free tree grammars strongly lexicalize tree adjoining grammars and themselves. 1 Introduction Tree adjoining grammars [TAG] (Joshi et al., 1969; Joshi ... Netherlands engelfri@liacs.nl Abstract Recently, it was shown (KUHLMANN, SATTA: Tree- adjoining grammars are not closed un- der strong lexicalization. Comput. Linguist.,...

Ngày tải lên: 07/03/2014, 18:20

... partial parse trees. To solve this problem, this section proposes a restricted version of the adjoining operation. 3.1 Adjoining Operation An adjoining operation is used in Tree- Adjoining Grammar ... inserts a tree into another tree. The inserted tree is called an auxiliary tree. Each auxiliary tree has a leaf called a foot which has the same nonterminal symbol as its root....

Ngày tải lên: 17/03/2014, 02:20

... MHG's. 1.1.1 Tree Adjoining Grammars Tree Adjoining Grammars differs from string rewriting sys- tems such as Context Free Grammars in that they generate trees. These trees are generated ... elementary trees using the operation of tree ad- junction. There are two types of elementary trees: initial and auxiliary. Linguistically, initial trees correspond to phrase structure...

Ngày tải lên: 17/03/2014, 20:20

... au- tomatically from a Treebank with a Bayesian model, their usefulness here suggests a greater potential for adapting to other languages and datasets. 2 Tree substitution grammars Tree substitution ... generate the negative data) 2. A Treebank grammar (Charniak, 1996) 3. A Bayesian-learned tree substitution grammar (Post and Gildea, 2009a) 2 2 The sampler was run with the default s...

Ngày tải lên: 23/03/2014, 16:20

... capturing two kinds of Cp, that correspond to the most salient discourse entities within the local transition and within the global focus of a text. Hahn and Strube (1997) estimate hierarchical ... Iida et al., 2007a, etc.) have been developed with less atten- tion given to such a problem. These methods ex- haustively search for an antecedent within the list of all candidate antecedents ......

Ngày tải lên: 30/03/2014, 23:20

... parameterize the calculation of θ k with γ as follows: θ k = Φ(h 0 ) · ¯α − γ k 3 . (3) The problem with using left-child chains is limiting them in number. With a left-recursive grammar, of course, ... T for x. Before inducing the left-child chains and allowable triples from the treebank, the trees are transformed with a selective left-corner transformation (Johnson and Roark, 2000)...

Ngày tải lên: 23/03/2014, 19:20

... define a tree adjoining grammar as follows. A tree adjoining grammar G is a paw (i,A) where i is a set of initial trees, and A is a set of auxiliary trees. A tree a ls an initial tree if it ... we can defoe the string Wl~W ~ where n derived tree in D(~) has • frontier wiYw ~. ff Y is •Ysode with with IsJ)ei X in some tree where adjoining is allowed, we introd...

Ngày tải lên: 24/03/2014, 01:21

... pair, (b) a tree transformation based mapping, and (c) a tree trans- ducer that performs the mapping. volve tree transformations either between two trees or a tree and a string. The tree transducer, ... language. A regular tree grammar (RTG) closely resembles a context free grammar (CFG), and is a way of de- scribing a language of trees. Formally, define T Σ as the set of trees wi...

Ngày tải lên: 19/02/2014, 19:20

Ngày tải lên: 20/02/2014, 18:20