Compounds in U niversal D ependencies: A Survey in Five E uropean Languages (2024)

Abstract: In Universal Dependencies, compounds, which we understand as words containing two or more roots, are represented according to tokenization, which reflects the orthographic conventions of the language. A closed compound (e.g. \textit{waterfall} ) corresponds to a single word in Universal Dependencies while a hyphenated compound ( \textit{father-in-law} ) and an open compound ( \textit{apple pie} ) to multiple words. The aim of this paper is to open a discussion on how to move towards a more consistent annotation of compounds.The solution we argue for is to represent the internal structure of all compound types analogously to syntactic phrases, which would not only increase the comparability of compounding within and across languages, but also allow comparisons of compounds and syntactic phrases.

## introduction compounding, as a word-formation process in which two or more words (bases, roots, or stems) are combined to form a new word @xcite , is used across languages @xcite . however, the term compound is not only used to refer to words that result from the combination of two words (cf. flowerpot) or are outputs of recursive compounding (e.g. german jahresabschlussprüfung 'end-of-the-year audit'), but also to words that are results of compounding happening in conjunction with derivation or conversion (e.g. the german adjective blauäugig 'blue-eyed'), foot_0 and to words that are both direct and indirect derivatives of these compounds (german blauäugigkeit 'blue-eyedness/naiveté'); cf. @xcite . the criteria for defining compounds (and especially distinguishing them from syntactic phrases) vary from language to language, but features with cross-linguistic validity include, besides the requirement of at least two roots, syntactic and semantic compactness. what is not decisive, on the other hand, is spelling. compounds are spelled as a single word (closed compounds; e.g. waterfall), or as several orthographic words joined by hyphens (hyphenated compounds; e.g. cyan-magenta-yellow-key) or separated by spaces (open compounds; e.g. apple pie). the present paper surveys how compounds are treated in universal dependencies (ud; version 2.12, @xcite . five languages, namely english, german, czech, latin, and russian, have been chosen for this pilot survey based on the working criteria that for each of the languages (a) at least one treebank is available in ud, (b) a lexical database exists that contains a non-negligible number of compounds (and can be used to identify compounds in the treebanks), and (c) the authors have a sufficient command of it. we show that the current treatment of compounds in ud, which is determined by the languages' orthographic conventions and by ud's tokenization rules, renders compounds difficult to identify in the data, hindering their comparison within and across languages. however, this paper is not limited to the mere unification of compound annotation according to the existing guidelines. our proposal is to annotate the relations between the compound's component parts by using the syntactic relations already implemented in ud, making the analogy between compounds and multi-word expressions and syntactic phrases explicit, which has already been pointed out in the literature. the paper is structured as follows. section 2 briefly summarizes those aspects of the linguistic discussion on compounding that are necessary for understanding the issues presented. an overview of the language data resources that contain compounds and are used in the paper is also provided. in section 3, we describe how compounds are currently handled in ud, exemplifying the general and language-specific problems of compounds. in section 4, we discuss steps that can be taken to make the annotation of compounds more coherent and to bring it closer to the way syntactic relations are annotated, but without losing the difference between compounding and syntax. future directions regarding the automation of compound identification and annotation are outlined to some extent. section 5 concludes the paper. ## concluding remarks in this paper, we explored the current treatment of compounds in ud in five languages. we observed that the handling of open and hyphenated compounds varies widely according to the particular language in question, and that closed compounds are taken into account in none of them. based on these observations and also the long-standing tradition of describing compounds from a syntactic perspective present in the linguistic literature, the objective of the paper was to open a discussion on whether a multilingual annotation scheme for compounds in ud that employs the dependency relations already in use is useful and what features it should have. the proposed scheme is currently being implemented in the data of the languages under study, and the aim is to extend it to other languages, which will inevitably result in modifications to individual aspects of the scheme. appendix: compounds annotated according to the current universal dependencies guidelines (left) vs. in line with the proposed annotation scheme (right) flowerpot noun root flower pot noun noun compound root flower -pot noun punct noun compound punct root flower+ pot noun noun compound: nmod root flower pot noun noun compound: nmod root flower -pot noun punct noun compound: nmod punct root wooden wall adj noun amod root stone wall noun noun compound root wooden wall adj noun amod root stone wall noun noun compound: nmod root altbekannt adj root älteste bekannt adj adj amod root alt+ bekannt adj adj compound: amod root älteste bekannt adj adj amod root dvacetitisícový adj root dvacet tisíc num noun compound root dvaceti+ tisícový num adj compound: nummod root dvacet tisíc num noun compound: nummod root pravoúhlý adj root pravý úhel adj noun amod root pravo+ úhlý adj adj compound: amod root pravý úhel adj noun amod root magnanimus adj root animus magnus adj noun amod root magn+ animus adj noun compound: amod root animus magnus noun adj amod root рукомойник adj root мыть руки verb noun obj root руко+ мойник noun adj compound: obj root мыть руки verb noun obj root