An empirically grounded expansion of the supersense inventory (2016)

Abstract: In this article we present an expansion of the supersense inventory. All new super-senses are extensions of members of the current inventory, which we postulate by identifying semantically coherent groups of synsets. We cover the expansion of the already-established supernsense inventory for nouns and verbs, the addition of coarse supersenses for adjectives in absence of a canonical supersense inventory, and super-senses for verbal satellites. We evaluate the viability of the new senses examining the annotation agreement, frequency and co-ocurrence patterns.

## introduction coarse word-sense disambiguation is a well established discipline @xcite @xcite @xcite that has acquired more momentum in the latter years under the name of supersense tagging (sst). sst uses a coarse sense inventory to label spans of variable word length @xcite @xcite . this coarse sense inventory is obtained from the list of word-net first beginners, i.e. the names of the lexicographer files that hold the synsets. however, lexicographer files were devised for practical reasons, namely as an organization method for the development of wordnet @xcite @xcite , and not as final target categories to annotate with or disambiguate from. nevertheless, the organization of lexicographer files is semantically motivated, and supersenses have proven useful for natural language processing such as metaphor detection or relation extraction @xcite @xcite . according to @xcite , supersenses extend the named entity recognition (ner) inventory so that the predictions of an sst model subsume the output of ner. @xcite provide a full ssi for prepositions. the current supersense inventory (henceforth ssi) enjoys de facto standardness, but in spite of its potential usefulness, it is used acritically. the current ssi provides 26 noun supersenes and 15 verb supersenses. adjective and adverb lexicographer files are disregarded. we provide a revision of the ssi by an extension of its supersenses using the danish wordnet as starting point. this revision is empirically backed by four evaluation criteria, namely inter-annotator agreement, sense frequency after adjucation, sense coocurrence, and ner compliance (whenever possible). note that we do not suggest merging existing supersenses, but only extending the current ssi in a backwards-compatible manner. we conduct our extension in three steps steps. first, we propose new supersenses when a projection between an eurowordnet (ewn) ontological type and a supersense is not univocal (section 2). second, we evaluate the distribution of supersenses in terms of agreement after an annotation task, frequency and sense-sense relations (section 4) and analyze the results across the different parts of speech (section 5). lastly, we suggest new supersenses (underlined in in the main contributions of this paper are i )a set of guidelines for the inclusion of new supernses in the ssi, ii) an empirically motivated expansion of the ssi with new senses for nouns, verbs and adjectives respectively, 1 and iii) a projection from ontological types to supersenses that can be used to enrich any wordnet that is not organized in lexi-cographer files or where synsets are not fully connected to princeton synsets. ## extending the supersense inventory this section describes the extension of the ssi that results from an analysis of projections into supersenses from ontological types, ensuing both retrocompatibility with the existing inventory (i.e. all new supersenses are extensions of an existing supersense), and compability with ner tags. we use the danish wordnet @xcite , dannet, as a starting point. dannet is not organized in lexicographer files. however, its synsets are associated to ontological types @xcite . we map from the ontological type of the synsets to a supersense. we establish a projection into supersenses with the following steps; if an ontological type t i : liquid+natural is a subtype of liquid), 3. and has enough support (in terms of how many synsets make up t i ), then we propose new supersense for t i as an extension of the supersense of t j . we consider the support to be substantial enough when a subtype has at least 500 synsets out of the 65k synsets in dannet and, and it makes up at least 12% of its parent supersense. we exemplify this method by explaining how we extend disease from state. the subtype property+physical+condition is associated to 527 synsets and makes up 70% of the synsets of the type condition. all the synsets of this subtype are diseases, and we propose the supersense disease as an extension of state, which is otherwise the supersense translation of condition. in addition to providing new supersenses for the main three lexical parts of speech, we devise three aditional tags for verbal satellites (collocations, particles and reflexive pronouns) as aid for verbal multiwords the annotation (cf. section 5.4). ## annotation task we perform an annotation task on 5,500 sentences from a danish contemporary corpus @xcite made up of newswire, parliamentary speech, blog posts, internet forum discussions, chatroom logs and magazine articles, plus the test section of the danish dependency treebank @xcite . any corpus choice imposes a bias, and we base the corpus choice on a twofold need: to tune the sense inventory to the needs of contemporary genres that are used for information extraction, without sacrificing its adequacy for more usual domains. generally speaking, another corpus choice would yield a different supersense expansion. the corpus was pre-annotated using the supersense projection list described in section 2. even though the size of the specific wordnet is a determining factor for the quality of the preannotation, it does not determine the coverage of the final supersense annotation, which provides full coverage because a ssi covers all content words. two in-house native annotators with a background in linguistics annotated the data, choosing the best pre-annotated sense or selecting a new one. a third annotator performed adjudication in case of disagreement. the overall kappa score before adjudication is 0.62. olsen et al. (2015) provide more details on the annotation task. the resulting data has been use for automatic supersense tagging by martínez alonso et al. (2015). ## metrics this section describes the metrics applied to the supersense-annotated corpus in order to assess the distribution of the new supersenses. ## conclusions and further work we suggest an extension of the ssi for the three main lexical parts of speech. we obtain new supersenses using a mapping from ontological types, and evaluating their distribution after an evaluation task. most of the new suggested senses satisfy the inclusion criteria we determine. in particular, we advocate for an inclusion of the senses n.document and n.institution, which improve ner compatibility. the extension method can be applied to any wordnet where the synsets are associated to ewn ontological types. nevertheless, the inclusion criteria might change when dealing with different languages or corpus types. moreover, the ssi proposed in this article can be applied retroactively to any ewn-aligned synset-annotated corpus. with regards to adjectives, the backoff a.all category still constitutes 40% of the annotated adjectives. in future work, we consider including senses from the germanet inventory, and experimenting with data-driven approaches to infer lexical categories for adjectives by means of their relations to other words in wordnets, following the work of @xcite , @xcite , @xcite and corpus-based approaches like @xcite .