some computational complexity results for synchronous context free grammars

Ngày tải lên: 23/03/2014, 17:20

Ngày tải lên: 23/03/2014, 16:20

Ngày tải lên: 23/03/2014, 16:20

... first O(n 4) results for the natural formalism of bilexical context- free grammar, and for AI- shawi's (1996) head automaton grammars. For the usual case, split head automaton grammars or ... show that the complexity is not so bad after all: • For bilexicalized context- free grammars, O(n 4) is possible. • The O(n 4) result also holds for head au- tomaton grammars. • For a very common ... assemble such subderivations into a full parse. 2 Notation for context- free grammars The reader is assumed to be familiar with context- free grammars. Our notation fol- 1Other relevant parsers simultaneously...

Ngày tải lên: 20/02/2014, 19:20

... Association for Computational Linguistics, pages 525–533, Uppsala, Sweden, 11-16 July 2010. c 2010 Association for Computational Linguistics Optimal rank reduction for Linear Context- Free Rewriting ... reduc- tion of a context- free grammar production into Chomsky normal form. However, in the LCFRS case some productions might not be reducible to r = 2, and the process stops at some larger value for r, ... Introduction Linear Context- Free Rewriting Systems (LCFRSs) have been introduced by Vijay- Shanker et al. (1987) for modeling the syntax of natural language. The formalism extends the generative capacity of context- free...

Ngày tải lên: 16/03/2014, 23:20

... losing the richer information offered by GHKM grammar. 6 Conclusion In this paper, we discussed several issues concerning decoding with synchronous context- free grammars, focusing on grammars resulting ... out rules with useful contextual information. In addi- tion, scope-filtering does not accommodate early lan- guage model state integration. We compare the two with an experiment. For the rest of the ... adding a heuristic to push up the cost of virtual items for fair comparison. For our experiments, we use an outside estimate as a heuristic for a virtual item. Consider the follow- ing rule binarization...

Ngày tải lên: 17/03/2014, 00:20

Ngày tải lên: 23/03/2014, 16:21

Ngày tải lên: 31/03/2014, 06:20

... extensions of context- free grammars. To appear in Mathematical Sys- tems Theory. Vijay-Shanker, K. and [)avid Weir. 1993b. Pars- ing some constrained grammar formalisms. To appear in Computational ... 1]) fori=0 ton-l for all node 71 in A U I labeled by ai+l call Add0/, t, i, i + 1) ;; induction (G'[i, i + k] = (;[i, j] + (:[j, i + k]) for k = 2 to n for i = 0 to n- k forj=i+ ... contains a node for every symbol in E U NT and an arc for every rule in P as follows. For each terminal and non-terminal symbol X in G create a node in LCG labeled with X. For each rule X...

Ngày tải lên: 08/03/2014, 07:20

... clarify the gen- erative capacities of such grammars and devices. Parallel multiple context- free grammars (pm- cfg's) and multiple context- free grammars (mcfg's) were introduced in ... "Generalized Context- Free Grammars and Multiple Context- Free Grammars& quot;, Trans. IEICE, J71-D-I, 5:758-765. Kasami, T. et al. 1988b. "On the Membership Prob- lem for Head Language ... "Generalized Phrase Structure Grammars, Head Grammars and Natural Language", Ph.D. dissertation, Stanford University. Rounds, W.C. 1969. " ;Context- Free Grammars on Trees", Proc....

Ngày tải lên: 08/03/2014, 07:20

... 1067–1076, Uppsala, Sweden, 11-16 July 2010. c 2010 Association for Computational Linguistics A Tree Transducer Model for Synchronous Tree-Adjoining Grammars Andreas Maletti Universitat Rovira i Virgili Avinguda ... as synchronous tree substitution gram- mars (STSG). We refer to Chiang (2006) for an introduction to synchronous devices. Let us recall the formal definition. An ex- tended tree transducer (for ... (2009) for a more detailed exposition to XTT. 5 Synchronous tree-adjoining grammar XTT are a simple, natural model for tree trans- formations, however they are not suitably ex- pressive for all...

Ngày tải lên: 17/03/2014, 00:20

... Italy satta@dei.unipd.it Abstract We consider the problem of parsing non-recursive context- free grammars, i.e., context- free grammars that generate finite languages. In natural language process- ing, this ... consists of symbols of the form for , and contains the following transitions: For each pair of rules and , contains: and . For each rule , contains: . Observe that for all PDAs constructed as ... ma- chine translation. We present two tabu- lar algorithms for parsing of non-recursive context- freegrammars, and show that they perform well in practical settings, despite the fact that this...

Ngày tải lên: 17/03/2014, 08:20

... berkeley, edu Abstract We present an algorithm for computing n-gram probabil- ities from stochastic context- free grammars, a procedure that can alleviate some of the standard problems associated ... generalizes straightforwardly to the more general Canonical Two-Form (Graham et al., 1980) format, and in the case of bigrams (n =- 2) it can even be modified to work directly for arbitrary SCFGs. ... 1 for a SCFG G, we immediately have an n-gram grammar for the language generated by G. Computing expectations Our goal now is to compute the substring expectations for a given grammar. Formalisms...

Ngày tải lên: 17/03/2014, 09:20

... ID/LP grammars. The results have im- plications for the description of free word order languages. 2 Introduction Context free grammars in immediate dominance and linear precedence format ... unordered, or ID/LP grammars, are e.xponentially more succinct than context- free grammars, by exhibiting a sequence (L,~) of finite languages such that the size of any CFG for L,~ must grow ... increasing context- free de- scriptions. ~Ve have the following theorem. Theorem 2 Consider the set Mn(n=) of all length n 2 strings of Mn. Then there is a constant c > 1 such that any context. free...

Ngày tải lên: 17/03/2014, 20:20

... approach for authorship attribution, the task of iden- tifying the author of a document, using probabilistic context- free grammars. Our approach involves building a probabilistic context- free grammar ... (discussed below). However, for some datasets, even this improvement was not sufficient to outperform the best baseline. The results for PCFG and PCFG-I demon- strate that syntactic information alone is ... model outper- forms the baseline for the Football dataset, PCFG- E outperforms the best baseline for the Poetry and Business datasets. For the Cricket and Travel datasets, the performance of the...

Ngày tải lên: 23/03/2014, 16:20

Ngày tải lên: 31/03/2014, 04:20

Ngày tải lên: 31/03/2014, 06:20

Ngày tải lên: 31/03/2014, 20:20

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Ngày tải lên: 13/05/2014, 10:21