On Hidden Semantic Relations between Nouns in W ord N et (2019)

Abstract: The paper presents an effort on transferability of noun–verb and noun–adjective derivative and semantic relations to noun-noun relations. The approach relies on information from semantic classes and existing inter-POS derivative and (morpho)semantic relations between noun and verb, and noun and adjective synsets. We have added semantic relations between nouns in WordNet that are indirectly linked via verbs and adjectives. Observations on the combination between the relations and semantic classes of nouns they link, may facilitate further efforts in assigning semantic properties to nouns pointing to their abilities to participate in predicate-argument structures.

## nouns in wordnet nouns in wordnet are organised within the superordinate / subordinate (hypernymy / hyponymy) hierarchy. the hierarchical semantic organisation is limited in depth, and distinguishing features are added to create lexical inheritance system where each word inherits the distinguishing features (attributes (modification), parts (meronymy), functions (predication) from its superordinates ( @xcite ). an example would be {diarist:1} [10011486-n] 3 , which, as a hyponym of {writer:2} [10801291n], is classified as noun.person and could be an agent of the verb synsets {write:1} [00993014v], {write:3} [01007027-v], write:4 [01031966v], and {write:5} [01691057-v] just like its hypernym. nouns are further related to verb synsets via derivative and/or (morpho)semantic relations -(morpho)semantic relations are applied to derivationally related noun -verb pairs, but not vice versa -not every derivationally related pair is (morpho)semantically linked, and to adjectivesvia derivative and pertainym relations (pertainym relations are usually applied to adj.pert adjectives, and nouns and adjectives are derivationally linked but not every derivationally linked pair noun -adjective is in pertainym relation). some nouns linked via a verb have an explicit link through hypernym/hyponym relation: (1) they can be two hyponyms of the same hypernym, e.g., the nouns {exhibition:1} [eng-30-00522145-n] and {exposure:3} [eng-30-00522537-n] are derivationally linked via the verb {expose:9; exhibit:3} @xcite , and are co-hyponyms of the noun synset {presentation:1; demonstration:1} 3 throughout the paper, the numbers of the literals follow those applied in the database used by the viewer hydra available at: http://dcl.bas.bg/bulnet/ . we do not give all literals and definitions due to space limitation but only ids of synsets acc. to pwn 3.0 -in square brackets, with pos marked at the end. there may be changes to semantic classes and (morpho)semantic relations between the pwn and the version on http://dcl.bas.bg/bulnet/ , for detail see @xcite . ## nouns linked via verb synsets in wordnet, verb and noun synsets are related via derivative and (morpho)semantic relations that link semantically similar verbs and nouns that share a stem with the same meaning. verbs impose selectional restrictions on the entities selected for their argument positions, particularly on characteristics of the nouns taking specific semantic roles. for example, the agent of cognitive verbs is expected to be animate and human (but not animal) while that of consumption verbs is animate but can be both human and animal. selectional restrictions also apply to complements -for example, motion verbs may have as their instrument nouns referring to vehicles and artifacts while their location or direction complement can be location, object or artifact. previous studies have further differentiated nouns which are linked via (morpho)semantic relations to different verb classes. @xcite and @xcite offer extension of the classification of deverbal nominals in portuguese drawing upon work on portuguese nominalisations @xcite where eight possible classes of eventive nominalisation have been proposed: action of, result of, physical result of, iteration of the act of, resulting state from, abstract result of, locative, collectivisation of. in previous work on the bulgarian wordnet, (morpho)semantic relations agent and undergoer were subdivided by taking into account the information about: verb and noun semantic classes, sentence frames encoding predicate-argument structure of the simple sentences that verbs can form, and noun suffixes, to formulate additional (morpho)semantic relations, such as experiencer, actor, recipient ((dimitrova, 2018)). @xcite have proposed subcategorisation of nouns by taking into account information from wordnet, verbnet, and framenet, which resulted in formulating subcategories such as: agent communicator, agent effector, agent experiencer, agent undergoer, artifact undergoer, etc. our proposal on introducing noun -noun semantic relations is based on the assumption that selectional restrictions are imposed not only by verbs but also by nouns derived from verbs such as nominalisations (e.g., writing), agentive nouns (e.g., writer), resultative nouns (e.g., written), etc. they are related to the source verb (e.g., write) not only via (morpho)semantic but also via derivative relations. we additionally take into account the relations between the semantic classes of the nouns linked through derivative relations via verb synsets. some -but not all -derivationally linked nouns are linked also via (morpho)semantic relations, as in ( 1 ) where {writing:2} and {writer:1} are event and agent, respectively, of {write:7}. other derivationally related nouns, however, such as {pen:3} below, are only derivationally (but not (morpho)semantically) linked: ex. {write:7; compose:3; pen:1} [01698271-v] verb.creation 'produce a literary work' has event: {writing:2; authorship:2; penning:1} [00929718-n] noun.act has agent: {writer:1; author:3} [10794014-n] noun.person derivative: {pen:3} [03906997-n] noun.artifact we assume that in many cases, the (morpho)semantic relations between the nouns may reflect the (morpho)semantic relations between the respective nouns and the verb, i.e., {writing:2} is an event nominal which has an agent {writer:1}. this assumption, however sketchy, can be tentatively extended to other derivationally related nouns; thus, we can add a semantic relation instrument to {pen:3}, which can be additionally related as an instrument for {writing:2; penning:1} and an instrument of {writer:1}: ex.: {writing:2; authorship:2; penning:1} noun.act has agent: {writer:1; author:3} noun.person has instrument: {pen:3} noun.artifact {writer:1; author:3} noun.person has instrument: {pen:3} noun.artifact some noun synsets have been already linked via hypernym/hyponym relations, f.ex. {squandering:1} ## nouns linked via adjective synsets an adjective denotes a property that is permanently inherent for an entity it modifies or refers to and is attributed to it in its entirety. therefore, an adjective can be defined as part-of-speech whose denotative function is realised through its connection to the noun. adjectives and nouns in wordnet are linked to each other mostly via derivative relations. descriptive adjectives (adj.all) are organised into clusters based on similarity of meaning (synonymy) and binary opposition (antonymy). relational adjectives (adj.pert) are (derivationally) related and linked to the synset which contains their source noun (as a literal). adjectival participles (adj.ppl) are related via participle relation to verbs they are derived from. thus, adjectives are organized via a set of relations that encode their properties of attribution, antonymy, similarity, derivation; fuzzynymy and thematic category (in the eu-rowordnet @xcite . however, from a derivational point of view, the distinction between descriptive and relational adjectives can be somewhat fuzzy, as descriptive adjectives can be also derived from nouns and refer to an attribute property of the defined entity (expressed by the noun). the property qualifies and characterises the entity expressed by the noun from which they are derived (e.g., pitiful pity, etc.). hence, an adjective may express one-sided relationship with the entity denoted by the motivating noun, though adjectives, which are derived from a noun, are motivated by it. in wordnet, an explicit noun -adjective relation with relational adjective (adj.pert) is pertainymy -an antisymmetric (derivative) relation between a relative adjective and the noun from which it is derived. the basic meaning of the relational adjective is determined by the noun from which it is derived, and these adjectives may inherit relations from the noun @xcite . some descriptive adjectives in wordnet may not be linked via pertainymy relation but can be derivationally related to a source noun. we have extracted noun synsets which are indirectly linked via adjectives -a noun is derivationally related to an adjective which, in its turn, is related via similarity relation to another adjective which is related to another noun. we applied the following scheme of extracted nouns: noun derivative adjective similar to adjective derivative noun. an example is given below where a nounnoun relation is assumed between {north wind:1; northerly:4; norther:1} and {north:3}. ex.: {north wind:1; norther:1} [11487950-n] noun.phenomenon derivative: {northerly:2; northern:1} [01601069-a] similar to: {north:2} has attribute: {north:3} 08561081-n noun.location {north wind:1; norther:1} is related to {north:3} some of these noun -noun pairs contain literals that are derivationally related (literals have the same root of at least one of the literals in the synset) though the synsets are not explicitly related via derivative relation; with others, only the adjectives are derivationally linked. we have identified only 31 noun -noun pairs that have at least one literal that is derivationally related, as in the example below. ex. {salinity:1} [04993604-n] noun.attribute derivative: {saline:1} [01074458-a] similar to: {salty:1} [01073822-a] derivative: {salt:7; table salt:1} [07813107-n] noun.food we have attempted to explore the dependence between the semantic classes of the nouns that are indirectly related via adjectives linked via similarity relation, to formulate noun -noun relations which were experimentally applied. ## conclusion the paper offers an approach to identification of semantic relations between nouns in wordnet that are indirectly linked via derivative relations through verbs and adjectives. in many cases, the derivationally related nouns preserve the semantics of the verb and the adjective, though there are some restrictions. we have formulated a basic set of semantic relations which mostly repeat the knowledge encoded on different levels of the network. noun -noun relations also reflect certain restrictions on nouns that are related to verbs of certain classes. the new relations assigned to nouns, will not only increase the inter-relatedness and density of wordnet relations but would allow us to assign new semantic properties to nouns. the work will continue with extending both the number of related noun -noun pairs and the set of the semantic relations formulated.