English. The purpose of this paper is the analysis of the auxiliary selection in intransitive verbs in Italian. The applied methodology consists in comparing the linguistic theory with the data extracted from two different annotated corpora: UD-IT and PoSTWITA-UD. The analyzed verbs have been classified in different semantic categories depending on the linguistic theory. The results confirm the theoretical assumptions and they could be considered as a starting point for many applicative tasks as Natural Language Generation.
In this work we have applied a corpus-based
approach to the investigation of the behavior of
Italian intransitive verbs for what concerns the
selection of the auxiliary verb. We considered two
corpora, namely UD-IT1 and PoSTWITA-UD
Intransitive verbs have been extensively studied
in both traditional grammar and linguistics, since
they do not always follow a standardized rule for
the auxiliary selection (see examples Section 2).
This fact could be the reason why their status is
not currently formalized enough in NLP, as long
as Italian is concerned. Among the most recent
investigation which use a corpus linguistic
methodology for the Italian language, we find
Our analysis starts from traditional Italian
grammars and then moves to the Auxiliary Selection
Hierarchy by
As in several other languages, in Italian one among two auxiliary verbs can be used together with the past participle verbal forms for compounding periphrastic tenses: avere (to have) and essere (to be), henceforth respectively indicated as A or E. When the verb is transitive, the auxiliary selection follows standard rules, depending on the diathesis: transitive verbs in active diathesis select A (e.g. Luca ha mangiato la mela – Luca ate the apple) while transitive verbs in passive diathesis select E (e.g. La mela e` mangiata da Luca – The apple is eaten by Luca).
Problems in the auxiliary selection occur
instead when the verb is intransitive. In fact,
provided that the behaviour of intransitive verbs
depends on both semantic and syntactic factors
Traditional and normative Italian grammars do
not provide an analysis of intransitive verbs and
auxiliary selection which could be formalized and
therefore usefully spent in NLP. In fact, they only
suggest lists of verbs that select A or E as
auxiliary, see e.g.
3The translation of the examples can be not correctly mapped on the English rules. When this happens the auxiliary is underlined.
4Sentences marked with * are ungrammatical.
the Unaccusative Hypothesis discussed in
For accounting for the behavior of intransitive verbs, in 1978, Perlmutter expressed the Unaccusative Hypothesis, which splits intransitive verbs in 2 subcategories: the unaccusative verbs and the unergative verbs. Perlmutter suggested that the unaccusative verbs are intransitive verbs whose grammatical subject is not an agent (e.g. La nave e` affondata – The ship is sunk), while unergative verbs are intransitive verbs whose grammatical subject is an agent (e.g. Giulia ha camminato - Giulia has walked).
More recently other linguists and researchers
analysed the topic, following two major lines:
Rosen that suggested to follow a syntactic-only
approach
A development of Perlmutter’s hypothesis supported by experimental and psycho-linguistic results can be found in Sorace (2000) that proposed an interesting modelling of the behaviour of intransitive verbs with respect to the selection of auxiliary for Italian too. This theory especially inspired our current work. 2.2
According to the theory proposed by Sorace, intransitive verbs can be hierarchically organized according to their different degree of telicity and agentivity. The more a verb is telic or agentive, the more it systematically selects the auxiliary verb E or A respectively.
This hierarchy of intransitive verbs, also known as Auxiliary Selection Hierarchy (ASH), includes categories defined on the basis of thematic and asASH category examples Change of location (maximum telicity) to go, to arrive Change of state to appear, to happen Continuation of pre-existing state to stay, to last Existence of state to exist, to seem Uncontrolled process to sleep, to rain Controlled process - motional to walk, to run Controlled process - non motional (maximum agentivity) to act, to play auxiliary selection selects E selects A pectual features. At one end of the ASH we find intransitive verbs which categorically select E as auxiliary, while at the other end we find intransitive verbs that always select A. The verbs between the two poles of the ASH can have an alternation in the auxiliary selection.
The ASH has been exploited in our work for classifying Italian intransitive verbs depending on its categories which are reported and exemplified in Table 1. This classification may seem wrong for verbs like ”to go” (andare), which are both agentive and unaccusative, but, as Sorace (2000:863) points out, the verbs that express a change of location have the highest degree of dinamicity and telicity, and they always select E as auxiliary.
3.1
In order to focus our study on the intransitive verbs
that are more commonly and competently used
by Italian speakers, we decided to extract the
intransitive verbs to be studied from the Nuovo
vocabolario di base della lingua italiana
For the present work, we considered only the verbs of the FO vocabulary, for a total of 51 intransitive verbs. But some of these verbs showed more than one single meaning and they could therefore be included in different categories of Sorace’s ASH. In order to carry out a disambiguation process, we used Babelnet5, a multilingual lexicalized semantic network and ontology. After the disambiguation process, the total number of verbs is 67. For what concerns intransitive pronominal verbs (e.g.rompersi, ”to break”), we decided not to take them into consideration for our research, since they always select the auxiliary E when constructed in compound tenses (eg. Gli occhiali si sono rotti (The glasses broke)). The choice to limit our research to the FO vocabulary is due to the fact that one should expect an expert usage of the verbs of this class also by an artificial speaker. 3.2
After having selected the verbs, we proceeded to
their classification, following the theory proposed
by
Table 2 shows some examples of Italian intransitive verbs belonging to the FO class, classified depending on the ASH by Sorace (2000).
Change of location andare (to go) Change of state apparire (to appear) Contin. pre-existing state rimanere (to last) Existence of state esistere (to exist) Uncontrolled process dormire (to sleep) Control. proc. (motion) camminare (to walk) Control. proc. (nonmotion) agire (to act) As mentioned above, the reference corpora for this work are the treebanks UD-IT and PoSTWITAUD, both annotated according to the Universal Dependencies (UD) format for what concerns morphology and syntax. Provided that UD is currently a standard de facto, the exploitation of this format allows us the application of the same methodology on other resources or languages.
The exploitation of both the data set is motivated by the need to extend our research on the larger available amount of data, and by the fact that UD-IT is representative of the standard Italian language, while PoSTWITA-UD represents the Italian language used in social media. This allows us to obtain a comprehensive set of results. 4.1
To extract the data concerning the auxiliary selection on UD-it and PoSWITA we used the Sets Treebank Search provided by the University of Turku, available for free at http:// bionlp-www.utu.fi/dep_search/.
We formulated an expression that allowed us to extract data related only to intransitive verbs that appear in the reference corpora at the past participle form together with an auxiliary verb (A or E). We then compared the data from the corpora against the classification based on the linguistic theory. 5
After the data extraction from UD-IT and PoSTWITA-UD, a first consideration is to be made about the percentages of intransitive verbs that select A or E in the two corpora.
As figure 1 shows, in UD-IT the auxiliary A is selected by 10% of the verbs and the auxiliary E by 69%. As long as PoSTWITA-UD is concerned (see fig.2), 49% of verbs select E and 9% select A in this corpus. The remaining percentages (in grey) are made up by the verbs that do not appear in compound tenses in the corpus and did not provide useful result for our study; they must be studied in larger corpora.
The overall results confirm the linguistic
theory for what concerns the distribution in
semantic classes organized by Sorace in hierarchy. In
fact, as Sorace affirms in
On the other hand, the auxiliary A is selected by verbs belonging to the categories of Uncontrolled process, Controlled motional Process and Controlled nonmotional process. This is an example taken from the corpus UD-It, for the verb ”to act”, agire in Italian: Se, a richiesta del mittente, il vettore emette la lettera di trasporto aereo, si considera, sino a prova contraria, che egli abbia agito in nome del mittente 6.
As fig. 4 shows, the results related to the
category of “controlled nonmotional process” show
that both auxiliary A and E can be admitted. This
fact is also mentioned by
The paper presents a study about the auxiliary
selection in intransitive verbs in Italian. Providing
that the qualitative description given by traditional
grammars does not allow the definition of a formal
model for the auxiliary selection, we considered a
study
We adopted in this study a corpus-based perspective and we tested our assumption on two treebanks for Italian respectively representig standard and social media language. The results confirm and validate the theory and they could be used to develop a formal model that can be exploited in a computational context.