binarization of synchronous context free grammars

... strings of Mn. Then there is a constant c > 1 such that any context. free grammar Gn generating Mn(n 2) must have sue f~(cn). Proof. This proof is really just a generalization of the proof of ... polynomiaUy bigger than the size of a grammar for the language itself. The proof of this claim rests on inspection of one of the standard proofs, say Hopcroft and Ullman [5]. The result is ... The number of strings in A is less than or equal to the number of ways of selecting one of the u strings. Consider the u string to the left of the boundary which z overlaps. Because of wraparound,...

Ngày tải lên: 17/03/2014, 20:20

... create new synchronous rules s U for each possible choice of subset U. In the worst case, this may result in an exponential blow-up of the source grammar. In the case of context- free grammars, ... probabilistic context- free grammar (Abney et al., 1999). This is sketched in what follows. We first compute the set of all nullable linked pairs of non- terminals of the underlying SCFG, that is, the set of all ... and by Stolcke (1995), which are extensions of parsing algorithms for probabilistic context- free grammars, and require considerably more involved proofs of correctness. Our method for computing...

Ngày tải lên: 23/03/2014, 16:20

Ngày tải lên: 23/03/2014, 17:20

Ngày tải lên: 31/03/2014, 04:20

Ngày tải lên: 31/03/2014, 06:20

... 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 ... Mental Representation of Grammatical Relations, J.Bresnan (ed.), MIT press:173-281. Kasami, T. et al. 1988a. "Generalized Context- Free Grammars and Multiple Context- Free Grammars& quot;, Trans. ... "On Multiple Context- Free Grammars& quot;, Theoretical Computer Science, 88, 2:191-229. Thatcher, J.W. 1967. "Characterizing Derivation Trees of Context- Free Grammars through a...

Ngày tải lên: 08/03/2014, 07:20

Ngày tải lên: 13/05/2014, 10:21

... lexicalization of CFG, without intro- ducing greater parsing complexity than CFG. Lexicalization of CFGs The lexicalization of grammar formalisms is of in- terest from a number of perspectives. It is of ... fifll advantage of the context- freeness of LCFC. This section describes a simple I)ottom-up recognizer for LCFG that is in the style of the CKY parser for (IT(I;. The virtue of this algo- rithm ... construc- tions of Earley parsers: Application to the production of O(n 6) Earley parsers for Tree Adjoining Grammars. In Proceedings of the Ist International Workshop on Tree Adjoining Grammars, ...

Ngày tải lên: 08/03/2014, 07:20

... 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 ... at all. This is usually not practical for GHKM grammars, because of the large number of nonterminals. 4 Adding flexibility 4.1 Glue rules Because of data sparsity, an SCFG extracted from data may ... cube-pruning, cannot be run in the presence of unary cycles. • The existence of many unary rules of the form “NP → NP, the NP” quickly fills a pruning bin with guesses of English words to insert without any...

Ngày tải lên: 17/03/2014, 00:20

... problem of parsing non-recursive context- free grammars, i.e., context- free grammars that generate finite languages. In natural language process- ing, this problem arises in several areas of application, ... Section 3 and the fact that is reduced. Parsing Non-Recursive Context- Free Grammars Mark-Jan Nederhof Faculty of Arts University of Groningen P.O. Box 716 NL-9700 AS Groningen, The Netherlands markjan@let.rug.nl Giorgio ... stochastic variant of an algorithm presented by Bar-Hillel et al. (1964), where it is shown that the intersection of a general context- free language and a regular language is still context- free. In the...

Ngày tải lên: 17/03/2014, 08:20

... stands for the expected count of occurrences of the substring w in a sentence of L.1 Proof Write the expectation for n-grams recursively in terms of those of order n - 1 and the conditional ... restaurants in the city of Berkeley. The train- ing corpus used had only 2500 sentences, with an average length of about 4.8 words/sentence. Our experiments made use of a context- free grammar hand-written ... 1970. An efficient context- free parsing algo- rithm. Communications of the ACM, 6(8):451-455. Susan L. Graham, Michael A. Harrison, and Walter L. Ruzzo. 1980. An improved context- freerecognizer....

Ngày tải lên: 17/03/2014, 09:20

... 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 for each author ... combination of word-level statistics and part -of- speech counts or n-grams. Baayen et al. (1996) demonstrate that the use of syntactic features from parse trees can improve the accu- racy of authorship ... the performance of the two methods was not statisti- cally significant at .05 significance level for any of the datasets, probably due to the small number of test samples. The performance of PCFG and...

Ngày tải lên: 23/03/2014, 16:20

Ngày tải lên: 31/03/2014, 06:20

Ngày tải lên: 31/03/2014, 06:20

Ngày tải lên: 31/03/2014, 20:20

Ngày tải lên: 31/03/2014, 21:20

... case of asynchronous bi- narization. However, synchronous binarization is constrained by the non-terminal reordering, lim- iting the possible binarization options. For in- stance, none of the binarization ... Pro- ceedings of the Annual Conference of the Association for Computational Linguistics. Liang Huang, Hao Zhang, Daniel Gildea, and Kevin Knight. 2008. Binarization of synchronous context- free gram- mars. ... synchronous rules that do not have a synchronous binarization. The primary contribution of this paper is to es- tablish that binarization of synchronous grammars need not be constrained by cross-lingual...

Ngày tải lên: 20/02/2014, 09:20

... those of the reversed Markov chain. 461 Efficient Parsing for Bilexical Context- Free Grammars and Head Automaton Grammars* Jason Eisner Dept. of Computer ~ Information Science University of ... • 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 special case of these grammars where an O(n ... of the form A[a] + ~. A T is just a derivation (proof tree) of lZ~n ,.o parse and its probability like that of any derivation we find is defined as the product of the prob- abilities of...

Ngày tải lên: 20/02/2014, 19:20

... run different types of grammars. Among them, the most successful are the CF grammars, the augmented phrase-structure grammars (APSGs), and the semantic grammars. All of them have different ... semantic grammars. The schema of the rule and the order of the operations are fixed, regardless of the chosen instance grammar. <TESTS> are evaluated before the application of a rule ... first form; - the anchor; -the list of parents: - the list of sons. Two trees T1 and T2 are called adjacent if the anchor of T1 is the first form of T2. 3.2. The algorithm The parser...

Ngày tải lên: 09/03/2014, 01:20

... The principle of bottom-up parsing is to reduce a sequence of phrases whose types match the right- hand side of a grammar rule to a phrase of the type of the left-hand side of the rule. To ... three grammars and two sentence sets used in these experiments have been obtained from Masaru Tomita and can be found in his book (Tomita 1986). Grammars I and II are toy grammars consisting of ... the number of edges produced. The motivation for this is that the working of a chart parser is tightly centered around the production and manipulation of edges, and that much of its work...

Ngày tải lên: 09/03/2014, 01:20