The Annotation Scheme of E nglish- C hinese Clause Alignment Corpus (2020)

Abstract: A clause complex consists of clauses, which are connected by component sharing relations and logic-semantic relations. Hence, clause-complex level structural transformations in translation are concerned with the expression adjustment of these two types of relations. In this paper, a formal scheme for tagging structural transformations in English-Chinese translation is designed. The annotation scheme include 3 steps operated on two grammatical levels: parsing an English clause complex into constructs and assembling construct translations on the clause complex level; translating constructs independently on the clause level. The assembling step involves 2 operations: performing operation functions and inserting Chinese words. The corpus annotation shows that it is feasible to divide structural transformations in English-Chinese translation into 2 levels. The corpus, which unfolds formally the operations of clause-complex level structural transformations, would help to improve the end-to-end translation of complicated sentences.

## introduction the grammatical levels of a natural language include morpheme, word, group/phrase, clause, and clause complex. units of a higher level are made up of units of a lower level. therefore, the central task for machine translation is language transformations on each grammatical level between languages. so far, there have been many studies on group/phrasal-and clausal-level structures and structural transformations. however, clause-complex level (cc-level) structures and structural transformations are far less discussed. @xcite describes the structures of english clause complex based on the theory of systemic-functional grammar. @xcite carries out an in-depth study on the structures of chinese complex sentence in comparison with english. @xcite points out that clauses should be considered as the translation unit in english-chinese translation. these studies are enlightening, but they are limited to theoretical illustrations and discussions. @xcite study clause complex for language engineering. they put forward and demonstrate the pta (parsing-translating-assembling) model for english-chinese translation on the cc-level, which is only a tentative idea and has not been tested through corpus annotation. @xcite clarify the concept of component sharing, define clause and clause complex based on this concept, and propose the design of the annotation scheme and specification for english-chinese clause alignment corpus (ecca corpus). yet, the details of the annotation scheme and specification of the ecca corpus still need further study and exploration, especially on the structural transformations between english and chinese clause complexes and their annotation. a clause complex consists of clauses, but many clauses are not connected linearly because there are shared components between them. in order to present the alignment of english and chinese clauses, it is necessary to show how english and chinese clauses correspond under various component sharing mechanisms. in ecca corpus, the correspondence relationship between english and chinese clauses is it is believed that ecca corpus is significant for theoretical linguistics and cognitive linguistics by providing samples for comparing cc-level structures and studying structural transformations between english and chinese. meanwhile, the corpus is believed to be significant in application. although machine translation has been greatly improved with data-driven approaches, it still fails to produce satisfying results when it comes across long sentences with complicated structures. this corpus explores the feasibility of and practical ways for mechanical transformations on the cc-level. it is hoped that the knowledge of cc-level structural transformations may help to improve the performance of machine translation in dealing with complicated sentences. the remainder of this paper is organized as follows: section 2 introduces the objective of annotation, section 3 introduces the annotation scheme, section 4 and 5 present operation functions and inserted chinese words applied in annotation; section 6 provides relevant statistical results, and section 7 concludes the paper. ## clause-complex level structural transformation the ecca corpus is designed to annotate cc-level structural transformations between english and chinese. in most linguistic theories, a clause complex is generally regarded as a group of clauses combined together based on logic-semantic relations. this being the case, cc-level structural transformations during translation should involve only reordering of clauses, which are usually organized in different logical ways between languages. however, there is another important transformation that should be noticed, i.e. the transformation of naming-telling structural relations. example 1: there are fewer than 100 potential customers for supercomputers priced between @xmath030 million : -::::::::::: presumably ::: the ::::::: cray-3 ::::: price ::::: range. ## design of the annotation scheme the cc-level structural transformations of example 1 are illustrated in figure 1 . in figure 1-(a), the english clause complex is firstly segmented into three constructs based on namingtelling structural analysis. the grey parts are namings, whose left-boundaries are marked by the symbol "|" below the line. tellings modifying or describing these namings take up new lines and are indented to the right after their namings. this way of demonstrating the naming-telling relationship is called newline-indent schema. each line in figure 1-(a ) is considered as one construct for making up the english clause complex, and they are translated independently in figure 1 the dash line arrow starts from the translation of a naming and points to its generalized form. the circles in figure 1-(c ) mark the insertion of the particle "的" and the linking verb "是". the graphic demonstration in figure 1 clearly displays how the english clause complex is transformed step by step into a chinese one. however, the demonstration is quite complicated, hard to be annotated and not convenient for statistical analysis. hence, a more formal annotation scheme for annotating structural transformations is designed. the formal annotation scheme follows the 3 steps in the graphic demonstration: (1) segment english clause complexes into constructs and display them in newline-indent schema; (2) translate independently each construct into chinese; (3) rearrange construct translations for a whole-sentence translation. the structural transformations are to be annotated at the end of each line of the whole-sentence translation. the parts that make up the whole-sentence translation are encoded as numbers, and the operations implemented on these parts are tagged as operation functions. in this way, structural as shown above, structural transformations are tagged after the symbol "//" at the end of each line. the numbers represent the parts making up the whole-sentence translation. for example, the number 2 of "2+的+1" represent the second line of construct translations, namely "价格在1500万美元至3000万 美元之间". the number 2.2 of "sum(2.2)+是+delt(3)" represent the second section of the second line of construct translations, namely "在1500万美元至3000万美元之间". in the annotation scheme, the translations of namings are usually processed as a single unit. when the translation of a naming is positioned within a construct translation, the construct translation is segmented by the translation of this naming into several parts, which includes the naming translation, the parts before and/or after the naming translation. these segments are named as component translations. the component translations on the n th line are encoded from left to right as n.1, n.2, and n.3 etc. in this example, the second line of construct translation contains the translation of a naming at its end, and thus it is divided into two components. the component before the naming translation is encoded as 2.1, while the naming translation is encoded as 2.2. from this example, it can be seen that the parts making up a whole-sentence translation include construct translations and component translations. these two types of constituents in translations are the basic units to be dealt with by operation functions, and thus they are called operation units in this paper. as for operation functions, they are used to mark the operations implemented on operation units. the symbol "+" means linking two operation units. the function "sum(2.2)" means turning the encoded component 2.2, namely "在1500万美元至3000万美元之间", into a more generalized expression "这 个区间". the function "delt(3)" means deleting the dash in the translation of the encoded construct 3, namely "-克雷3号机大概的价格范围". the designing of operation functions will be discussed in detail in section 4. additionally, it is noted that the translation of every construct in the second step is independent of its context. certainly, the disambiguation of a certain word still need reference to its context, but it is not allowed to add extra words, delete words or change the structures based on the context. ## operation functions there are two types of operations for cc-level structural transformations: (1) processing and assembling the operation units, and (2) inserting chinese words. the first type of operation is annotated as operation functions, which will be discussed in this section. the second type of operation will be discussed in section 5. operation functions are written in the format of functionname(x) or functionname(x,y), in which functionname specifies the operation to be implemented, while x and y specify the objects to be processed, which are all called operation units. twenty operation functions are designed, which involve 6 types of operations: link, reorder, add, delete, rewrite, and substitute. the 20 operation functions are listed in operation types operation functions link concatenate(x,y) (i.e. x+y) reorder demonstrated with the codes of operation units add corcj(x), corcj2(x) , prd(x) delete ignore(x) (i.e. *x), delcj(x) , delcj2(x) , delpn(x) , delt(x) rewrite det(x) , ndet(x) , sum(x) , pron(x) , rel(x) , paren(x) , n2v(x) substitute rpw(x,y) , r2n(x,y) , n2r(x,y) of all these functions, link and reorder are common operations in almost all processed whole-sentence translations. the usage of these two functions is shown above in example 1. other functions are divided into two types based on their adjustments to clause complex structures. some of the two classes are discussed with examples in the following subsections. due to limited space, the functions not discussed in this paper can be referred to in @xcite . ## inserted chinese words the inserted chinese words are function words such as linking verbs, particles, conjunctions and prepositions. the chinese words can be classified into 2 types based on their functions: (1) words indicative proceedings of the 19th china national conference on computational linguistics, pages 1035-1044, hainan, china, october 30 -novermber 1, 2020. (c) technical committee on computational linguistics, chinese information processing society of china c c l 2 0 2 0 of argumentative relations between operation units, and (2) words indicative of logical relations between operation units. ## statistical data so far, we have annotated 2108 clause complexes on 136 documents from english penn treebank. of the annotated clause complexes, 336 contain only one clause. of the clause complexes containing more than one clause, 532 do not involved cc-level structural transformations. therefore, only a total of 1240 clause complexes are annotated with relevant functions and chinese words, accounting for 58.82% of the 2108 clause complexes. the frequency of each operation function in ecca corpus is shown in ## conclusions and discussions component sharing relations and logic-semantic relations are organized differently in english and chinese clause complexes. as a result, during english-chinese translation, it is necessary to adjust the expressions of these two relations with some structural transformations on the clause complex level. this paper divides english-chinese clause complex translation into two grammatical levels. on the clause complex level, an english clause complex is parsed into constructs, and the translations of these constructs are assembled into a whole-sentence translation. on the clause level, each construct is translated independently. the two-level translation mechanism, including operation functions and inserted chinese words used in the assembling step, has been designed formally and proved feasible with corpus manual annotation. by designing the two-level translation mechanism, this paper follows a common strategy for ai problem solving, namely to decompose a complicated task into sequential simple tasks. it is believed that this mechanism could reduce the demanded data scale and calculation complexity for machine-learningbased machine translation, since the task of translating a sentence is decomposed into simple tasks of translating and assembling shorter constructs. meanwhile, although the mechanism cannot produce perfect results in some cases, it is an explainable translation process and thus is worth further exploring. the work present in this paper is only initial. in the future, efforts will be made to enlarge the corpus size, improve the quality of annotated translations, provide multiple translation alternatives, design algorithms for realizing operation functions and discover linguistic knowledge based on the ecca corpus. proceedings of the 19th china national conference on computational linguistics, pages 1035-1044, hainan, china, october 30 -novermber 1, 2020. (c) technical committee on computational linguistics, chinese information processing society of china c c l 2 0 2 0