Joshi, Aravind K., L. Levy, and M. Takahashi. 1975. Tree Adjunct Grammars. Journal of Computer and System Sciences.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....that a probabillstic form of lexicalized tree adjoining grammar provides just such a seamless combination. I begin with a brief description of lexicalizod tree adjoining grammar, and then present its probabilistic generalization and the vantages of the resulting formalism. lccadjoining grammar [Joshi et al. 1975], or TAG, is a generalization el context free grammar that has been proposed as a useful formalism for tbc study of natural tauglages. A tree adjoining grammar com priscs two sets of elementary structures: initial trees and auxiliary trees. See Figure 3, in which initial and auxiliary trees are ....

Arerind Joshi, Leon Levy, and M Taka- hashi. Tree adjunct grammars. Journal of the Computer and System Sciences, 10, 1975.

....of tree adjoining grammars and its advantages over context free grammars are presented. All the components of TAG3P , and an example using bias on the 6 multiplexer problem, are discussed in Sections 3 and 4. Section 5 draws conclusions. 2 Tree Adjoining Grammars Joshi and his colleagues in [10] proposed tree adjunct grammars, the original form of tree adjoining grammars (TAG) Adjunction was the only tree rewriting operation. Later, the substitution operation was added and the new formalism became known as TAG. Although the addition of substitution did not change the strong and weak ....

Joshi, A. K.. Levy, L. S., and Takahashi, M.: Tree Adjunct Grammars. Journal of Computer and System Sciences, 10 (1), (1975) 136-163.

....of parses using this representation. We then consider the same issues where lig is used as the formalism for representing parses. We conclude by comparing these results with those for existing tag parsing algorithms. 2 Tree Adjoining Grammars Ta is a tree generating formalism introduced in [Joshi eta . 1975]. A tag is defined by a finite set of elementary trees that are composed by means of the operations of tree adjunction and substitution. In this paper, we only consider the use of the adjunction operation. 384 Definition 2.1 A tag, G, is denoted 6= vN, v, LA) where VN is a finite set of ....

A. K. Joshi, L. S. Levy, and M. Takahashi. Tree adjunct grammars. J. Cornput. Syst. Sci., 10(1), 1975.

....GP program representations in structure preserving ways. 3. To use ACO, a fixed graph representation is needed beforehand to construct the parse tree. It was not obvious what this graph should be. Recently, we came across a formalism in natural languages known as Tree adjunct grammars (TAGs) [6]. We found that it can be more easily combined with ACO than the conventional parse tree can be used in GP. Actually, any linear representation of the parse tree can be used for ACO. However, we decided to use TAGs to build upon our current work using TAGs as a powerful representational language ....

....parse tree. GGGP has a number of advantages, both in problem representation and search space restriction, and in the greater degree of context preservation provided by the parse tree. D. Tree Adjunct Grammar Tree adjunct grammars (TAGs) are tree rewriting systems. They were first introduced in [6]. More recently, the theoretically redundant but practically convenient operation of substitution has been added; the resultant grammars are known as tree adjoining grammars. Treeadjoining grammars have been used successfully in natural language processing; and a comprehensive survey of TAGs can ....

[Article contains additional citation context not shown here]

A. K. Joshi, L. S. Levy, and M. Takahashi. Tree adjunct grammars. Journal of Computer and System Sciences, 10(1), 1975.

....way the string laguagc of a rewriting grammar in the Chomsky hicrrehy is defined. Definition 3.3 (Ycc Languages and String Languages) 77, e tree language and string language of a RN[ C, denoted Sqcc adjoidng grintartars wcrc introduced m a formalism for linguis [ic description by Joshi ct al. [10], 9] Various formal and compntaimml properties of TAG s were studied in [17] its linguistic rc[cwnce was dcmom stinted in [12] OThis hierarchy is different from [he hicrarchy of meta 15L s invented md studied cx.cnsivcly by Weir in rain context rcc rcc grammars il [15] vriablcs are used in ....

Aravind K. Joshi, Leon Levy, ad Masako Takhashi. Tree adjunct grammars. Journal of Uomputev and System Sci- ences, 10:136-163, 1975.

....linear context free rewriting systems is equal to the class of output lan guages of deterministic tree walking transducers [1] A number of other equivalences have already been established. In [10] it was shown that linear contextfree rewriting systems and multicomponent tree adjoining grammars [6] generate the same string lan guages. The multiple context free grammars of [7] are equivalent to linear context free systems. This follows I would like to thank Joost Engelfriet for drawing my attention to context free hypergraph grammars and their relationship to deterministic tree walking ....

....by a context free grammar. 2. Their composition operations are size preserving, i.e. when two or more substructures are combined only a bounded amount of structure is added or deleted. 136 Examples of formalisms that. satisfy these condi tions are head grammars [8] tree adjoining gram mars [6], multicomponent tree adjoining grammars [6] and context free hypergraph grammars. It was shown [9] that a system satisfying the above conditions generates languages that are semilinear and can be recognized in polynomial time. The definition of linear context free rewriting systems is ....

[Article contains additional citation context not shown here]

A. K. Joshi, L. S. Levy, and M. Takahashi. Tree adjunct grammars. J. Cornput. Syst. Sci., 10(1), 1975.

....this method. In this paper, the latest progress of AntTAG are reported. AntTAG is a hybrid approach which takes advantages of Tree adjunct Grammar (TAG) representation and the search strategy of Ant Colony Optimization (ACO) 2, 10] TAGs are tree writing systems and were first introduced in [7]. A comprehensive survey of TAGs can be found in [8] In [5, 6] Hoai et al. proposed Tree Adjunct Grammar Guided Genetic Programming (TAGGGP) introducing TAGs into Grammar Guided Genetic Programming (GGGP) TAGGGP outperforms GGGP on some problems they studied. ACO is inspired by the collective ....

....Elementary trees of TAG grammar 2 Background Due to limited space, we are unable to give detailed background knowledge here. We can only briefly describe two most important issues: Tree Adjunct Grammar and pheromone table. 2. 1 Tree adjunct grammar The formal definition of TAG can be found in [7]. The operation in TAG is the adjunction of trees. Adjunction can build a new (derived) tree from an auxiliary tree # and another tree (initial, auxiliary or derived tree) #. If tree # has a nonterminal node labeled A and # is a A type tree then the adjunction of # and # is as follows. First, the ....

Aravind K. Joshi, L. S. Levy, and M. Takahashi. Tree adjunct grammars. Journal of Computer and System Sciences, 10(1), 1975. 7

....perhaps, because this function is too simple. However, GGGP with G1 seemed to converge more quickly. Consequently, it seems desirable to find a mechanism to set grammatical bias directly on the tree sets. In [5] and [6] we introduced such a representation, in which tree adjunct grammars (TAGs) [10], tree rewriting systems, are used to set bias on the tree sets of grammars. 6. CONCLUSIONS FUTURE WORK In this paper we have empirically shown that Antonisse s conjecture [2] is not always true in the context of grammar guided genetic programming. GGGP with ambiguous grammars sometimes ....

A.K. Joshi, L.S. Levy, and M. Takahashi, "Tree Adjunct Grammars", Journal of Computer and System Sciences, Vol. 10:1, pp. 136-163, 1975.

....De nite Clause Grammars (DCGs) does respect to CFGs. Keywords: Natural Language Parsing, TAG, DCG. 1 Introduction In the literature, the grammatical formalism Tree Adjoining Grammars (TAGs) are propagated to be adequate for natural language description. The class of TAGs was rst introduced in [JLT75]; since then, formal and computational properties of this class have been extensively investigated, and the linguistic relevance of TAGs has been discussed in the literature as well. A TAG grammar is a tree generating formalism rather than a string generating system like traditional Chomky s ....

Joshi, A. K.; Levy, L. S.; and Takahashi, M. (1975) Tree Adjunct Grammars. Journal of Computer System and Science 10(1), 136-63.

....information in the lexicon that can be considered purely syntactic. Furthermore, the time complexity of the parsers can be reduced when applying to lexicalized formalisms. Among well known formalisms in the literature, TAG de ned by Joshi, Levy and Takahashi is a naturally lexicalized formalism [5]. The TAG formalism is a context sensitive one, therefore, account for an important computational cost compared to CFG, see Nederhof in [7] for more details. In general, the class CFG is not naturally lexicalized, since we can de ne rules without terminal symbols in its right side. We can ....

Joshi, A. K., Levy, L., Takahashi, M.: Tree Adjunct Grammars. Journal of Computer and Systems Science 10 (1975) 136-163

....concise, contextually appropriate utterances, including both speech and concurrent nonverbal behavior, by applying a simple, uniform and efficient decision making strategy. This strategy exploits the lexicalized tree adjoining grammar (LTAG) formalism in which SPUD s grammar is represented [Joshi et al. 1975, Schabes, 1990] LTAG grammars derive sentences by incorporating meaningful elements one by one into a provisional syntactic structure. SPUD makes these choices head first and incrementally, in the order its grammar provides. At each stage of derivation, SPUD determines both the intended ....

Joshi, A. K., Levy, L., and Takahashi, M. (1975). Tree adjunct grammars. Journal of the Computer and System Sciences, 10:136--163.

....uses this property: it defines modules (or partial proof nets) which consist in entries for words, describing both the category of the word and its behavior when interacting with other words. Then the natural question of comparing the generative power of such grammars with Tree Adjoining Grammars [JLT75], as [JK96] pointed some links out, arises. To answer this question, we propose a logical formalization of TAGs in the framework of linear logic proof nets. We aim to model trees and operations on these trees with a restricted part of proof nets (included in the intuitionistic ones) and we show ....

....the way we model operations on proof nets. As replying to the second section, the fourth one allows us to come back from proof nets to trees. Finally, section 5 shows examples of how the definitions and properties work. 1 Definitions 1. 1 TAG First, extending the original definition of TAG [JLT75] with the substitution operation as in [SAJ88, AFV96] we get: Definition 1. A TAG is a 5 uple (V N #V T #S#I#A) where: 1. VN is a finite set of non terminal symbols, 2. V T is a finite set of terminal symbols, 3. S is a distinguished non terminal symbol, the start symbol, 4. I is a set of ....

[Article contains additional citation context not shown here]

Aravind K. Joshi, Leon S. Levy, and Masako Takahashi. Tree adjunct grammars. Journal of Computer and System Sciences, 10(1):136--163, 1975.

....approach that is different from that shown above which uses context free rules. The approach uses the notion of tree rewriting as defined in the Lexicalized Tree Adjoining Grammar (LTAG) formalism (Joshi and Schabes, 1992) 1 which re 1 This is a lexicalized version of Tree Adjoining Grammar (Joshi et al. 1975; Joshi, 1985) tains the notion of lexicalization that is crucial in the success of a statistical parser while permitting a simple definition of tag dictionary. For example, the parse in Figure 1 can be generated by assigning the structured labels shown in Figure 2 to each word in the sentence ....

A. K. Joshi, L. Levy, and M. Takahashi. 1975. Tree Adjunct Grammars. Journal of Computer and System Sciences.

.... of a marker makes very easy the checking of the property defining the string in our languages (knowing the center , we can directy check the relation between the two halves of the strings) Note also the difference between the previous classes of contextual grammars and the tree adjoint grammars, [11], which can generate all context free languages (hence also the mirror image based languages like M 8 ) but, in the basic variant, are not able to cover the multiple agreement languages like M 3 ; M 4 , see, e.g. 18] As we have emphasized in Section 4 (this is also pointed out in [16] in ....

A. K. Joshi, L. S. Levy, M. Takahashi, Tree adjunct grammars, Journal of Computer and System Sciences, 19, 1 (1975), 136 -- 163.

....systems, Chomsky grammars, pure grammars, Lindenmayer systems, etc. are based on the operation of rewriting, see, e.g. 13] 14] However, there are several classes of grammars whose basic ingredient is the adjoining operation. The most important of them are the tree adjoining grammars (TAG) [5]) the contextual grammars ( 7] and the insertion grammars ( 4] all three introduced as models of constructions in natural languages. The insertion grammars (in [4] they are called semi contextual grammars) are somewhat intermediate between Chomsky context sensitive grammars (where the ....

A. K. Joshi, L. S. Levy, M. Takahashi, Tree adjunct grammars, J. Computer System Sci., 19 (1975) 136 -- 163.

....reusability, user friendly graphical interface, easy installation procedure and recycling of existing grammars, see for instance (Erbach Uszkoreit, 1990) for a overview of these problems. Focusing on these features, we present a set of freely available tools dedicated to the LTAG formalism (Joshi et al. 1975) which aims to be an alternative to the XTAG system (XTAG research group, 1998) The LTAG workbench is still an on going work and we hope that it will appear enough promising to give rise to interests and possible contributions from the LTAG community. We present first the outlines of the current ....

JOSHI A., LEVI L. & TAKAHASHI M. (1975). Tree adjunct grammars. Journal of the Computer and System Sciences.

....This provides just the amount of non locality needed for an adequate analysis of scrambling. To illustrate this a local TDG for some German scrambling data is presented. 1. Introduction Scrambling in German poses a problem for most grammar formalisms. Neither Tree Adjoining Grammar (TAG, Joshi et al. 1975) nor even linear context free rewriting systems (LCFRS, Weir, 1988) are powerful enough to deal with scrambling and the free word order in German (see Becker et al. 1992) Becker et al. 1991) propose a scrambling analysis with non local multicomponent TAG (MCTAG, Weir, 1988) and (Rambow Lee, ....

JOSHI A. K., LEVY L. S. & TAKAHASHI M. (1975). Tree Adjunct Grammars. Journal of Computer and System Science, 10, 136--163.

....languages O(n 4 ) unambiguous TAGs I would like to thank Aravind Joshi, Carlos Prolo and Fei Xia for their help and suggestions. This work was partially supported by NSF Grant SBR 8920230. O(n) bounded state TAGs e.g. the usual grammar G where L(G) fa n b n e c n d n j n 0g (see (Joshi et al. 1975)) The grammar factors are as follows: Schabes Earley style algorithm takes O(jAjjI[AjNn 6 ) worst case time and O(jA[IjNn 4 ) worst case space, where n is the length of the input, A is the set of auxiliary trees, I is the set of initial trees and N is maximum number of nodes in an elementary ....

JOSHI A. K., LEVY L. & TAKAHASHI M. (1975). Tree Adjunct Grammars. Journal of Computer and System Sciences.

....were later shown to be awed, the result is nonetheless upheld by Shieber s [35] proof that Swiss German s crossing dependencies are not even weakly context free. Interestingly, 40] show the equivalence of four independently developed formalisms CCG, Tree Adjoining Grammar (TAG) [17], Head Grammars [32] and Linear Indexed 1 J. of Language and Computation, Vol. 0 No. 0, pp. 1 22 0000 c Oxford University Press Relating Categorial Type Logics and CCG through simulation 2 Grammars (LIG) 10] which have mildly context sensitive generative power and are capable of capturing ....

Aravind Joshi, Leon Levy, and M. Takahashi. Tree-adjunct grammars. Journal of Computer Systems Science, 10:136-163, 1975.

....an operation distinct from substitution. The candidate weadvocate here is that of Tree Adjoining Grammar (TAG) a system which, as the name suggests, includes adjoining, an operation which rewrites the single node of some elementary tree by a recursive piece of structure called an auxiliary tree (Joshi et al. 1975# Joshi, 1987) What is crucial for our purposes is that the adjoining operation allows us to introduce adjunction structures into purely lexical elementary trees, whichbyhypothesis lackany explicit structural representation of these nonargumental elements. In particular we can use an auxiliary ....

Joshi, Aravind K., Leon Levy, and MasakoTakahashi. 1975. Tree adjunct grammars. Journal of the Computer and System Sciences 10(1):136--163.

....covered the rich determiner system of English, we do cover a large subset, both in terms of the phenomena handled and in terms of corpus coverage. The analysis presented in this paper is fully implemented as part of a Feature Based, Lexicalized Tree Adjoining Grammar (FB LTAG) for English [1, 3, 5]. Previous approaches to syntactic determiner ordering (e.g. 4] have simply divided determiners into subcategories (e.g. predet, det, postdet) This type of approach is inadequate because it allows ungrammatical sequences like all what no, and misses the finer distinctions among particular ....

Joshi, A., Levy, L. and Takahashi, M. 1975. Tree adjunct grammars. In Journal of Computer and System Sciences.

....general, more e#cient to process. In this paper we showhowtyping can assist in the validation of untyped feature structure speci#cations. The technique we suggest in this paper is incorporated into the XTAG grammar development system, which is based on the Tree Adjoining Grammar #TAG# formalism #Joshi, Levy, and Takahashi, 1975#, extended to include lexicalization #Schabes, Abeill#e, and Joshi, 1988# and uni#cationbased feature structures #Vijay Shanker and Joshi, 1991#. Tree Adjoining Languages fall into the class of mildly context sensitive languages, and as such are more powerful than context free languages. The TAG ....

Joshi, Aravind K., L. Levy, and M. Takahashi. 1975. Tree Adjunct Grammars. Journal of Computer and System Sciences.

....as an attempt to bring together fundamental ideas, some coming from Tree Adjoining Grammars (TAG) and others from Categorial Grammars (CG) in order to overcome the speci c limitations of each of these formalisms. The computational and linguistic relevance of TAG lies in its adjunction operation (Joshi et al. 1975; Kroch and Joshi, 1985) but the simplicity of its mechanism has a counterpart in the in ation of the lexicons that are required for expressing all grammatical phenomena of a language. Every time that a word is used in a new syntactic context, which can di er only by word order for example, a new ....

A. K. Joshi, L. S. Levy, and M. Takahashi. 1975. Tree adjunct grammars. Journal of Computer and System Sciences, 10(1):136-163.

....analysis. I will use the terms lexical analysis and clause union interchangeably. 2. 3 Tree Adjoining Grammar and Lexicalism Recent work in nontransformational frameworks such as LFG (Bresnan and Kaplan, 1982) HPSG (Pollard and Sag, 1994) categorial systems, and tree adjoining grammar (TAG) (Joshi et al. 1975), has stressed the importance of the lexicon in the development of a theory of syntax, and these approaches share a desire to locate syntactic variation within and between languages in the lexical component of grammar. In TAG based linguistic theories 7 (Kroch, 1987; Frank, 1992) the lexicalist ....

Joshi, A., Levy, L., and Takahashi, M. (1975). Tree adjunct grammars. J. Comput. Syst. Sci., 10:136-- 163.

....of O(n 6 ) Quite recently, an O(n 3 M (n) algorithm has been proposed. The algorithm presented in this paper improves the run time of the recent result using an entirely different approach. 1 Introduction The Tree Adjoining Grammar (TAG) formalism was introduced by Joshi, Levy and Takahashi (1975). TAGs are tree generating systems, and are strictly more powerful than context free grammars. They belong to the class of mildly context sensitive grammars (Joshi, et al. 1991) They have been found to be good grammatical systems for natural languages (Kroch, Joshi, 1985) The first polynomial ....

A.K. Joshi, L.S. Levy, and M. Takahashi, Tree Adjunct Grammars, Journal of Computer and System Sciences, 10(1), 1975.

....is context free) A second example 1 Unless specified otherwise, we will use this term broadly and include in it the variations introduced by the Barriers framework of Chomsky (1986a) 9 is constituted by the linguistic theories that have been developed on the bases of TAG. The TAG formalism (Joshi et al. 1975; Joshi, 1985) is a tree rewriting system, so that the elementary structures of the grammar are trees. The extended domain of locality of the elementary structures (extended with respect to the string rewriting rules of a CFG) has two important consequences: ffl The grammar can be lexicalized, ....

Joshi, A., Levy, L., and Takahashi, M. (1975). Tree adjunct grammars. J. Comput. Syst. Sci., 10:136--163.

....more efficient to process. In this paper we show how typing can assist in the validation of untyped feature structure specifications. The technique we suggest in this paper is incorporated into the XTAG grammar development system, which is based on the Tree Adjoining Grammar (TAG) formalism (Joshi, Levy, and Takahashi, 1975), extended to include lexicalization (Schabes, Abeill e, and Joshi, 1988) and unificationbased feature structures (Vijay Shanker and Joshi, 1991) Tree Adjoining Languages fall into the class of mildly context sensitive languages, and as such are more powerful than context free languages. The TAG ....

Joshi, Aravind K., L. Levy, and M. Takahashi. 1975. Tree Adjunct Grammars. Journal of Computer and System Sciences.

....an operation distinct from substitution. The candidate we advocate here is that of Tree Adjoining Grammar (TAG) a system which, as the name suggests, includes adjoining, an operation which rewrites the single node of some elementary tree by a recursive piece of structure called an auxiliary tree (Joshi et al. 1975; Joshi, 1987) What is crucial for our purposes is that the adjoining operation allows us to introduce adjunction structures into purely lexical elementary trees, which by hypothesis lack any explicit structural representation of these nonargumental elements. In particular we can use an auxiliary ....

Joshi, Aravind K., Leon Levy, and Masako Takahashi. 1975. Tree adjunct grammars. Journal of the Computer and System Sciences 10(1):136-163.

....by an NSF Grant, SBR 8920230. wide coverage grammars. 2. The XTAG English grammar The XTAG English grammar (XTAG Group, 1998) is a wide coverage English grammar based on the lexicalized Tree Adjoining Grammar (LTAG) formalism. LTAG is a lexicalized mildlycontext sensitive tree rewriting system (Joshi et al. 1975). It is capable of supporting structural descriptions not supported by context free grammars. In LTAG, each piece of syntactic structure is encoded in an object called an elementary tree, which is lexicalized. Parsing is accomplished by combining these elementary trees selected by the words in ....

A. J. Joshi, L. S. Levy, and M. Takahashi. 1975. Tree adjunct grammars. In Journal of Computer and System Sciences.

....about, e.g. agreement between syntactic units. Lexical trees fall into two classes: initial and auxiliary trees. After extraction, semantic information from the sentence plan is added to the tree feature structures; this is called enriching the trees. The Tree Adjoining Grammar (TAG) formalism [5] used to build the phrase structure tree allows to construct derived composite trees by combining two trees (lexical or derived) via two elementary operations, substitution and adjunction. We say that an inner tree is inserted into an outer tree. Substitution attaches an initial tree at the ....

Aravind K. Joshi, L. S. Levy and M. Takahashi, Tree Adjunct Grammars, J. Comput. Syst. Sci., Vol.10, 1975

....from the field of computational linguistics that provides an interesting perspective from which to view results in the production literature. This approach is known as tree adjoining grammars (TAGs) and is associated with Aravind Joshi and his colleagues and students (Frank, 1992; Joshi, 1985; Joshi, Levy, Takahashi, 1975; Kroch Joshi, 1985) The important fundamental feature of this approach is that it assumes the existence of primitive, basic syntactic trees, which are combined in various constrained ways. This description of TAG will highlight the characteristics of elementary trees, the ways they may be ....

Joshi, A.K., Levy, L., & Takahashi, M. (1975). Tree adjunct grammars. Journal of the Computer and System Sciences, 10, 136-163.

....[9,3] has revealed a very close formal rela tionship between the grammatical formalisms of Tree Ad joining Cramm (TAC s) and Head Cramars (C s) In this paper we examine whether they have the same power of linguistic description. TAG s were first intro duced in 1975 by Joshi, Levy and Takahashi[1] and investigated further in [2,4,8] HG s were first introduced by Pollard[5] TAG s and HG s were introduced to capture certain structural properties of natural languages. These formalisms were developed independently and are notationally quite different. TAG s deal with a set of elementary ....

Joshi, A. K., Levy, L. S., and Takahashi, M. Tree Adjunct Grammars. Journal of Computer and System Sciences 10(1), March, 1975.

.... briefly describe TAG s, which have the following important properties: 1) we can represent the usual transformational relations more or less directly in TAG s, 2) the power of TAG s is only slightly more than that of context free grammars (CFG s) in what appears to be.Just the right way, and (3) TAG s are powerful enough to characterize dependencies (e. subcateRortzatton, as in verb subcategorization, and filler gap dependencies, as in the case of moved constitutents in wh questions) which miRht GPSG: Generalized phrase structure grammar, PLG: Phrase linking grammar, and LFG: ....

.... formal properties of TAG s, GPSG s,PLG s, and LFG s, in particular, concerning (1) the types of languages, reflecting different patterns of dependencies that can or cannot be generated by the different types of grammars, 2) the degree of free word ordering permitted by different grammars, and (3) parsing complexity of the different grammars. 2.TREE ADJOINING GRAMMAR(TAG) A tree adjoining grammar (TAG) G = I,A) consists of two finite sets of elementary trees. The trees in I will be called the initial trees and the trees in A, the auxiliary trees. A tree is an initial tree if the root ....

[Article contains additional citation context not shown here]

Joshi, A.K., Levy, L.S., and Takahashi, Mo,"Tree adjunct grammars", Journal of the Computer and System Sciences,1975.

.... of the CKY parsing algorithm [7, 14] This formulation clarifies the structure of the algorithm, leading to a revised complexity analysis and an optimization in one case, and lays a formal foundation for generalizing this method to more complex cases using, for example, tree adjoining grammars [4, 6]. Molecules like RNAs or proteins are sequences of building blocks nucleotides for RNA or amino acids for proteins but they do not lie in straight lines in space. Rather, bonds, which we will call self contacts, may form between nonadjacent members of the sequence, folding it into a certain ....

A. K. Joshi, L.S. Levy, and M. Takahashi. Tree adjunct grammars. J. Comp. Sys. Sci., 10(1):136--163, 1975.

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Aravind K. Joshi, L. Levy, and M. Takahashi. Tree Adjunct Grammars. Journal of Computer and System Sciences, 1975.

....section, we give a brief introduction to the LTAG formalism and to a system named LexTract, which was built to extract LTAGs from the Treebanks [Xia, 1999; Xia et al. 2000a] 3. 1 The Grammar Formalism LTAGs are based on the Tree Adjoining Grammar formalism developed by Joshi and his colleagues [Joshi et al. 1975; Joshi and Schabes, 1997] The primitive elements of an LTAG are elementary trees (etrees) Each etree is associated with a lexical item (called the anchor of the tree) on its frontier. LTAGs possess many desirable properties, such as the Extended Domain of Locality, which allows the ....

Aravind K. Joshi, L. Levy, and M. Takahashi. Tree Adjunct Grammars. Journal of Computer and System Sciences, 1975.

....node. In this case, the adjunction of an auxiliary tree is mandatory. OA is used as a notational shorthand for OA(A) If there are no substitution nodes in the elementary trees and if there are no constraints on adjoining, then we have the pure (old) Tree Adjoining Grammar (TAG) as described in [Joshi et al..1975]. The operation of substitution and the constraints on adjoining are both needed for linguistic reasons. Constraints on adjoining are also needed for formal reasons in order to obtain some closure properties. 2.2 Derivation in TAG We now define by an example the notion of derivation in a TAG. ....

Aravind K. Joshi, L. S. Levy, and M. Takahashi. 1975. Tree adjunct grammars. Journal of Computer and System Sciences, 10(1).

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Joshi, Aravind K., L. Levy, and M. Takahashi. 1975. Tree Adjunct Grammars. Journal of Computer and System Sciences.

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A. K. Joshi, L. Levy and M. Takahashi: "Tree Adjunct Grammars," J. Comput. System Sci., 10, 1, pp.136163, 1975.

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Joshi, Aravind K., L. Levy and M. Takahashi. (1975). Tree adjunct grammar. In Journal of Computer and System Science, vol. 21, no. 2, 1975.

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Joshi, A.K., Levy, L., and Takahashi, M. Tree adjunct grammars, JCSS, 10(1):136--163, 1975.

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A.J. Joshi, L. Levy, and M. Takahashi. Tree adjunct grammars. Journal of Computer and System Science, 1975.

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Joshi, A. K., L. S. Levy and M. Takahashi, Tree adjunct grammars, Journal of Computer and System Sciences 10 (1975), pp. 136--63.

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Aravind K. Joshi, L. Levy, and M. Takahashi. Tree adjunct grammars. Journal of the Computer and System Sciences, 10:136--163, 1975.

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A. K. loshi, L. S. Levy, and M. Talmhashi. Tree adjunct grammars. J. Comput. Syst. Sci., 10(1), 1975.

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A. K. Joshi, L. S. Levy and M. Takahashi, `Tree adjunct grammars', Journal of Computer and System Sciences, 10, 136--163 (1975).

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A. Joshi, L. Levy, and M. Takahashi, "Tree Adjunct Gram- mars," J. Computer and System Sciences, Vol. 10, No. 1.,

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Aravind K. Joshi, L. Levy, and M. Takahashi. Tree Adjunct Grammars. Journal of Computer and System Sciences, 1975.

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Joshi, A., L. Levy and M. Takahashi. 1975. Tree Adjunct Grammars. Journal of the Computer and System Sciences 10: 136-163.

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Aravind K. Joshi, L. Levy, and M. Takahashi. 1975. Tree Adjunct Grammars. Journal of Computer and System Sciences.

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