A R omanian Treebank Annotated with Verbal Multiword Expressions (2022)

Abstract: In this paper we present a new version of the Romanian journalistic treebank annotated with verbal multiword expressions of four types: idioms, light verb constructions, reflexive verbs and inherently adpositional verbs, the last type being recently added to the corpus. These types have been defined and characterized in a multilingual setting (the PARSEME guidelines for annotating verbal multiword expressions). We present the annotation methodologies and offer quantitative data about the expressions occurring in the corpus. We discuss the characteristics of these expressions, with special reference to the difficulties they raise for the automatic processing of Romanian text, as well as for human usage. Special attention is paid to the challenges in the annotation of the inherently adpositional verbs. The corpus is freely available in two formats (CUPT and RDF), as well as queryable using a SPARQL endpoint.

## introduction language resources of the type electronic corpora annotated with syntactic information (most of the times on top of lexical and morphological annotations), i.e. treebanks, are now quite common for languages and even dialects. if a decade ago the number of treebanks for various languages was rather scarce, now we can find many such resources, though still of a modest size. the situation has greatly improved given the existence of two major multilingual initiatives: universal dependencies 1 (ud) @xcite and parseme cost action @xcite , two open community efforts, active in improving and enhancing their results. ud is an ini-1 universaldependencies.org tiative created with the aim of offering the instruments for a cross-lingual description at the morphologic and syntactic levels. seventeen universal parts of speech (e.g., noun, verb, aux, pron, adj, etc.) and a set of morphological features (e.g., number, gender, tense, etc.) are used for the morphologic level, and 37 universal relations (e.g., nsubj for the nominal subject, csubj for the clausal subject, obj for the nominal direct object, ccomp for the clausal direct object, etc.) are defined for the syntactic description. these morphologic instruments are considered enough for the description of any language, while the inventory of syntactic relations is admittedly universal, but subtypes of the 37 universal relations are accepted for a more specific syntactic analysis: e.g., nsubj:pass for the nominal subject in passive constructions for the languages that do have passive; 26 such subtypes have been defined so far, which are specific to one or more languages. in its last release (may 2022), ud boasts 228 treebanks for 130 languages, all freely available. the existence of treebanks for various languages released through ud has offered the premise for the development of automatic tools @xcite that can be trained on these treebanks and further used to annotate new corpora. this paved the way to initiatives such as parseme, in which new corpora, collected according to certain requirements (such as text genre, size, license, etc.), were automatically morphosyntactically annotated with such tools and further enriched with a new level of annotation, i.e. semantic: verbal multiword expressions (vmwes) were manually annotated following the same guidelines for all languages, that identify universal, quasi-universal and languagespecific vmwe types. within parseme, treebanks for 26 languages were annotated and one of them is for romanian. there are already several treebanks for roma-nian freely available: within ud, there is the romanian reference treebank (rrt) (barbu mititelu, 2018) (containing sentences from various text genres), romanian non-standard treebank @xcite (containing sentences from old texts or from folklore), the medical treebank simonero @xcite ) (which has an extra annotation level: medical entities of the types anatomical parts, chemicals, disorders and procedures) and the treebank of the aromanian dialect of romanian art @xcite . there is also another treebank, unavailable in ud, legal-nero @xcite , which has a further level containing gold annotations for five entity classes: organizations, locations, persons, time expressions and legal resources mentioned in legal documents. in this paper we present a new version of the romanian treebank, whose annotation started in parseme and which has recently been enriched with a new type of verbal expressions, i.e. inherently adpositional verbs. we call this corpus parseme-ro. we will first outline the context of development of this corpus, namely the parseme shared tasks (section 2), then present some idiosyncrasies displayed by the verbal expressions occurring in the corpus (section 3). we describe the corpus itself: its levels of annotation (section 4) and problems raised by annotating the new type of verbal expressions. some general statistics about the corpus and statistics about the vmwe types in the corpus are given in section 6, before concluding the paper. based on the experience gathered in the annotation for edition 1.0, as well as on the types of vmwes identified in the corpora, starting with edition 1.1 of parseme, the following types of vmwes have been annotated @xcite : ## characteristics of vmwes contributing to their (automatic) processing difficulty mwes are defined as "idiosyncratic interpretations that cross word boundaries (or spaces)" @xcite . they are "lexical items that: (a) can be decomposed into multiple lexemes; and (b) display lexical, syntactic, semantic, pragmatic and/or statistical idiomaticity" @xcite . the identification of vmwes in texts is a wellknown challenge for nlp applications, because of their special characteristics, including discontinuity, overlaps, non-compositionality, heterogeneity, and syntactic variability. they are problematic not only for machines, but also for humans: on the one hand, for students learning a second language and, on the other, for native speakers who are exposed to rarer expressions. one key characteristic of a vmwe is for it to be idiomatic. this property refers to "markedness or deviation from the basic properties of the component lexemes, and applies at the lexical, syntactic, semantic, pragmatic, and/or statistical levels" @xcite . lexical idiomaticity is displayed when one or more components of a vmwe are not part of the conventional lexicon or are not used outside the respective vmwes: for romanian, this is the case of the boldfaced words in the vmwes a-s , i aduce aminte ('to remember') or a avea habar ('to have a clue'). various romanian vmwes conserve lexical or semantic archaisms as the boldfaced words in the following expressions show: aduce aminte ('remind'), nu da în brânci ('have a soft job'), da ortul popii ('die'), nu avea habar ('have a clue'), veni de hac ('bear down'), bȃga de seamȃ ('notice'), nu da inima ghes (be reluctant to), scoate la ivealȃ ('reveal'), lua la rost ('chide'), etc. on the morphological level, there are vmwes that display restrictions on the paradigmatic realization of the verbal head with respect to one or more morphosyntactic features, such as person, number, tense, mood, polarity, etc. or with respect to possible derived forms: e.g. ro a nu privi cu ochi buni (not watch with eyes good, 'to regard with disfavour') is always used with the negative marker nu 'not'. in addition, there are vmwes that contain obsolete inflectional and derived forms, such as a bate câmpii (beat the fields 'to beat around the bush') (in which câmpi foot_4 is an old plural form of the word câmp, whose current plural form is câmpuri), a pune pe roate (pun on wheels 'to get on its feet') (in which roate is an old plural form of the word roatȃ, whose current plural form is rot , i), a lua cu binis , orul (take with wellness diminutive 'to let down easily') (the diminutive noun binis , orul is not currently used outside expressions) @xcite . syntactic idiomaticity arises when the syntax of the vmwe is not derived directly from that of its components. the syntactic level of description would include any restrictions on the word order of the vmwe components and of the possible dependents. for example, in the ro vmwe a da ortul popii (give coin-the to priest-the 'to die') the object ortul always precedes the indirect object popii, though romanian allows for any order of the direct and indirect object in case of their co-occurrence (though with different pragmatic salience in each case). semantic idiomaticity means noncompositionality of the expression, i.e. the meaning of a mwe is not explicitly derivable from the semantics of its parts. vmwes displaying semantic idiomaticity have frequently components with metaphoric (a lua taurul de coarne take the bull of horns 'to take the bull by the horns'), hyperbolic (a crȃpa de frig crack by cold 'to be very cold') or metonymic (a nu ridica un deget not lift a finger 'not to lift a finger') meaning in addition to their literal meaning. semantic idiomaticity may imply either the fact that the expression's meaning is given rather by one of the components (see the descriptions for lvcs in section 2) or the fact that the global sense of the expressions has nothing to do with the senses of the components: e.g. the words making up the vid a tȃia frunzȃ la câini (cut leaf for dogs 'to dally') have no semantic relation to the sense of the expression. pragmatic idiomaticity occurs when a vmwe is associated with a fixed set of situations or a particular context of use: see the case of greetings that are specific to the different parts of the day: e.g. en good morning, ro noapte bunȃ (night good 'good night'), etc. statistical idiomaticity is triggered by the high frequency a particular combination of words occurs with: e.g. en black and white is semantically equivalent to ro alb-negru (white-black), in spite of the lack of the conjunction and of the reversed order of the two components. all these characteristics of expressions may prevent their correct automatic interpretation, but also their understanding in inter-human communication, needless to say their grammatically correct and semantically adequate usage by second language learners. these justify the necessity for (computational) linguists' focusing more on phraseology. the insufficient attention paid to them leads to inconsistent terminology, inconsistent treatment of such units in lexicography, partial descriptions in grammars and dictionaries and little focus on it in textbooks, though, admittedly, expressions are a touchstone of language command. ## annotation levels the parseme corpus for romanian (parseme-ro) is journalistic and was automatically tokenized, part-of-speech tagged, lemmatized and syntactically parsed using udpipe @xcite trained on rrt. in a first step (consisting of all three annotation phases pertaining to the participation in the three editions of the shared tasks), the annotation of the different types of vmwes was manual: the annotators identified and classified the vmwes belonging to the lvc.full, lvc.cause, vid and irv types. in the first edition four annotators were involved, in the second one there were three, and two participated to the last edition. each annotator had a portion of the morphosyntactically processed corpus to annotate: using the flat platform foot_5 @xcite , their task was to read the text, to spot a potential vmwe and, using the decision tree and the battery of tests from the parseme guidelines, to decide if the respective string was indeed a vmwe and specify its type. only for a small portion of the data (2500 sentences) was the annotation double, so as to measure the agreement between annotators @xcite . in a second, recent, step, iavs were annotated in parseme-ro. this time, the annotation was automatic, followed by manual validation and correction, in two phases. starting from the list of 1,725 adpositional verbs created by geanȃ (2013), all their occurrences in the corpus were identified and annotated as iavs. this was done automatically by using a python script that performed a global search of the iavs tokens within the corpus text. this search was enhanced to include a span window in order to capture situations where other tokens were interleaved with the actual iav in the corpus text. in cases where several matches were found for one of the tokens of the iav (this applies mostly to prepositions) the principle of the minimum distance length between the tokens was used. finally, based on these matches, the corpus tokens found to correspond to an iav were automatically annotated. then the first phase of the manual validation and correction step followed: two annota-tors, students in linguistics, were presented with all automatically annotated instances and, using an annotation platform, they could modify the annotations in the sense of deleting expressions or adjusting their size (i.e. adding or removing parts), using the brat tool @xcite , integrated in the relate platform @xcite . several sources of errors could be identified in the automatic annotation of iavs: consistency of annotation was ensured differently for each step: for the annotation in the context of the shared tasks, we used the consistency checking tools made available by the organizers @xcite , helping to spot the skipped occurrences of vmwes, as well as inconsistent type assignment of the same vmwe. for the step involving the annotation of iavs, we envisaged a second phase of the validation and correction step: all cases of agreement between the two student annotators were considered correct decisions (see the 2,981 cases marked as "both annots" in geanȃ (2013: p. 46) defines adpositional verbs as constructions in which the verb is "capable of getting a prepositional complement", where the complement is defined as an obligatory valence of the verb, irrespective of its semantics. this means that in the class of adpositional verbs we can have examples in which the adposition is part of an adverbial, e.g. a place adverbial: i live in london. geanȃ (2013: p. 118) further distinguishes between adpositional verbs using as criterion the type of adposition, namely: testing the two types of examples against the parseme criterion, we notice that in the case of functional adpositions the test holds, as one cannot ask about the circumstances of the verbal event using the verb only, not also the adposition: *când cross-lingual_tests/070_inherently_ adpositional_verbs__lb_iav_rb_ no. of sentences 56,664 no. of tokens 1,014,908 no. of words 806,540 no. of verbal lemmas 61,323 no. of unique verbal lemma 3,815 given these remarks on the types of iavs annotated in parseme-ro, we consider that the annotated data will need some further refinement: adpositional verbs will need to be further classified into two subtypes: iav.functional and iav.semilexical. the existence of subclasses inside a class is not new for parseme: see the two subtypes of lvcs, namely lvc.full and lvc.cuase (section 2). however, continuing the parseme custom of testing classes and subclasses against data in more languages before coining them officially, the next step we envisage is collaborating with teams working on iavs for other languages, so as to share findings. ## corpus statistics general information about the corpus size is available in the most frequent (usually ten foot_7 ) verbs in each type of vmwes are enumerated below, and, between brackets, their frequency with the respective type of vmwes; for verbs that are among the 20 most frequent ones in the corpus, we also indicate between brackets the relative frequency with which they are used in that type of vmwes: type number irv 3.826 lvc.cause 182 lvc.full 516 vid 1.644 iav 3.311 total 9479 we notice that verbs may tend to occur in one type of vmwes, but there are many exceptions, with the verb pune (put) occurring with lvc.cause, lvc.full, vid and iav expressions, and the verb lua (take) occurring with three types: lvc.full, vid and iav. there are others occurring only with lvc.full and vid: avea (have), face (make, do), da (give). all are verbs with rich polisemy, sometimes even bleached in frozen combinations. ## conclusions the new version of the parseme-ro corpus comes with a new type of vmwes: iav. such expressions are widely spread in the corpus: they represent a third of the total number of vmwes occurring therein. this makes them an important phenomenon to be made explicit in a corpus. a comparative analysis of the cases when the same combination verb + adposition is either annotated as an iav or not will be carried out, coupled with grammatical and semantic characteristics of the context, to better understand what the specific contexts for iavs are. so far, only verbal iavs have been annotated in parseme-ro, while vmwes iavs (iavmwes) are left for further investigations. prior to this, we consider that the status of iavs needs to get clarified, as our analysis of such expressions has shown that the type could be further classified into two subtypes: iav.functional and iav.semi-lexical. the new version of parseme-ro will be made fully and freely available in the first annual release within parseme, scheduled for mid 2022, in a format that will be agreed upon within the community. it is also available on our website of language resources in linked data format foot_9 and can be queried using the sparql endpoint foot_10 .