Variation in U niversal D ependencies annotation: A token-based typological case study on adpossessive constructions (2020)

Abstract: In this paper we present a method for identifying and analyzing adnominal possessive constructions in 66 Universal Dependencies treebanks. We classify adpossessive constructions in terms of their morphological type (locus of marking) and present a workflow for detecting and analyzing them typologically. Based on a preliminary evaluation, the algorithm works fairly reliably in adpossessive constructions that are morphologically marked. However, it performs rather poorly in adpossessive constructions that are not marked morphologically, so-called zero-marked constructions, because of difficulties in identifying these constructions with the current annotation. We also discuss different types of variation in annotation in different treebanks for the same language and for treebanks of closely related languages. The research focuses on one well-circumscribed and universal construction in the hope of generating more interest in using UD for cross-linguistic comparison and for contributing towards developing yet more consistent annotation of constructions in the UD annotation scheme.

## introduction universal dependencies (ud) and other multilingual language corpora have in many ways boosted crosslinguistic corpus research to a completely new level, enabling novel developments, for instance, in the so-called token-based typology @xcite . one of the aims of ud is to provide universal annotations for various syntactic relations (called universal dependency relations in ud), parts-of-speech, and grammatical categories (features in ud), which then enable productive cross-linguistic comparison. however, the currently available universal dependency relations are what from a typological perspective could be described as higher-level functions, such as subject, object, nominal modifiers, and adjectival modifiers. in addition, the dependency relations are not consistently based on universal construction types, as observed and recommended by @xcite , but often on language-specific strategies. for instance, nominal modifiers encompass constructions that have a wide range of functions in the world's languages, including possession, but it is not easy to compare them in the ud treebanks owing to variation in annotation across treebanks. such variation has been noted earlier as well, in relation to research on linguistic complexity @xcite . in this paper we focus on one well-defined and universal construction, namely adnominal possessives (also called adpossessive constructions or possessive noun phrases). adpossessive constructions are syntactically noun phrases whose head is a noun and that may have a noun or a pronoun as a dependent modifier. semantically the relation between the head and the dependent in these constructions expresses typically ownership (alienable possession), such as my car, part-whole relationships (including inalienable possession), such as my hand, and kinship relationships, such as my daughter. syntactic adpossessive constructions can also be used for various other functions depending on each language @xcite @xcite . in adpossessive constructions the syntactic dependent is semantically the possessor and the syntactic head is semantically the possessee. for example, in the construction my daughter the syntactic head is the possessee daughter and the dependent is the possessor my. we aim to research how these constructions can be identified in the ud treebanks. our analyses are based on a sample of 63 treebanks from 44 languages that have a large corpus in the ud. the selected languages represent ten language families from eurasia, africa, and the pacific (see ## results our algorithm identified altogether 724 694 adpossessive constructions in the data. the distribution of different morphological types across sample languages are presented in figure 2 as percent shares. dependent marking is clearly a dominating pattern overall. it occurs in all but four languages, occurs with at least 65% share in 39 languages, and is the only type in 18 languages. this strong domination of dependent marking is an areal feature. head and dependent marking in adpossessive constructions are fairly evenly distributed in the world's languages, but dependent marking dominates in eurasia and africa and head marking in the americas @xcite . in our data head marking is a relatively minor type, occurring only in six languages, but where it occurs it is a dominating pattern (in five languages with 65% share or more). these figures for head and dependent marking clearly reflect the fact that languages of eurasia are overrepresented in the sample. double marking is a rare and minor type occurring in only three languages (finnish, turkish, and uyghur) and only as a minor type in each of them (with less than 20% shares in each). zero marking, on the other hand, is a common pattern, occurring in 23 sample languages (52% of languages); however, it is only a minor pattern in most of these languages, being fairly common only in indonesian and estonian. in addition, zero marking seems to occur in languages that have also dependent marking, but in this sample this is clearly a side-effect of dependent marking dominating in adpossessive constructions overall. overall the process for identifying adpossessive constructions in the sampled treebanks required us to define up to 1,000 tags (on average 14 per treebank), including pos tags, specific features, dependency relations, and lemmas for pronouns and adpositions in several cases. figure 3 presents a boxplot of how many tags were needed to identify adpossessive constructions in the treebanks, grouped into language families. 6 this figure represents only those languages included in the tagchart. the boxplot suggests that languages in most families required roughly 10-15 tags, in a few languages around 20 tags, and in the turkic family more than 30 tags. this variation may reflect real diversity in adpossessive constructions in these language families, but it may at least in part reflect also the variation in the annotation of adpossessive constructions in the treebanks, suggesting potential places of concern in terms of annotation consistency. figure 3 : number of tags needed in each language family for identifying adpossessive constructions. it was not possible to estimate automatically the performance of the algorithm, including the range and incidence of false positives and negatives. the main reason for this is that there is no gold standard available, which precludes comparing our results against such benchmark. whether such a benchmark will be reached in the future is an open question. however, to achieve at least a very preliminary and crude idea of the algorithm's performance, we manually analyzed a few dozen adpossessive constructions in four languages from four different language families. the results of this evaluation are presented in ## discussion and conclusion our analyses suggest that there are different types of variations in how adpossessive constructions are annotated across ud treebanks. to some extent this is expected because languages sometimes have several different morphosyntactic ways for expressing adnominal possession and across languages this diversity is multiplied. on the other hand, adnominal possession is a prominent and universal syntactic construction in the languages of the world, and reducing unnecessary variation in annotation would enable more efficient identification of these constructions by linguists and language technologists. given the variation in annotation it is natural that our method for identifying adpossessive constructions contained both false positives and false negatives, as even the limited evaluation suggested. false negatives were rare and they seem structurally quite similar with adpossessive constructions albeit expressing some other function which is difficult to delineate from adpossessive constructions based on the current annotation. false negatives, on the other hand, result largely from errors in the algorithm, from our insufficient knowledge of the languages and treebanks, and from problems with the current annotation of the treebanks, as discussed in relation to zero marking in indonesian and vietnamese. a further challenge, for instance, in vietnamese, is possessive classifiers @xcite , but since we did not have sufficient knowledge about this type of construction, we did not even try detecting them. overall, since in many languages morphological annotation had to be used for identifying adpossessive constructions, it is possible that in quite many languages potential zero-marked adpossessive constructions went unnoticed. the success and usefulness of ud and other multilingual language corpora rest largely on their annotation schemes. in this paper we have reported on a typological case study of identifying and analyzing adpossessive constructions in 63 ud treebanks. this construction represent much variation in annotation even in different treebanks of the same language and in treebanks of closely related languages. in line with earlier research @xcite , our results suggest that there are some limitations to the extent which ud can currently be used for cross-linguistic research, especially concerning zeromarked constructions; however, the results also indicate that for morphologically marked adpossessive constructions, ud can currently be used quite reliably for token-based typological research.