Resolving Multiple Hyperonymy (2023)

Abstract: WordNet contains a fair number of synsets with multiple hyperonyms. In parent–child relations, a child can have only one parent (ancestor). Consequently, multiple hyperonymy represents distinct semantic relations. In order to reclassify the multiple hyperonyms, we define a small set of new semantic relations (such as function, origin and form) that cover the various instances of multiple hyperonyms. The synsets with multiple hyperonyms that lead to the same root and belong to the same semantic class were grouped automatically, resulting in semantic patterns that serve as a point of departure for the classification. The proposed changes are based on semantic analysis and may involve the redefinition of one or several multiple hyperonymy relations to new ones, the removal of one or several multiple hyperonymy relations, and rarely the addition of a new hyperonymy relation. As a result, we incorporate the newly defined semantic relations that resolve the former multiple hyperonymy relations and propose an updated WordNet structure without multiple hyperonyms. The resulting WordNet structure without multiple hyperonyms may be used for a variety of purposes that require proper inheritance.

## introduction wordnet @xcite is a lexical semantic network that encodes human knowledge about synonyms -words (or multi-word expressions) denoting the same concept -and the semantic relationships between the concepts. the nodes of the semantic network are synonym sets (synsets), which are connected by arcs representing semantic relations. the hyperonymy relation (and its inverse relation, hyponymy) connects more general concepts to more specific ones and organizes noun synsets in hierarchies, with the most abstract concepts at the root of the trees and the most specific concepts at the leaves of the trees @xcite . hyperonymy and hyponymy relations satisfy properties for asymmetry and transitivity @xcite . for instance, if bird is a hyperonym of parrot, then parrot is not a hyperonym of bird; similarly, if parrot is a hyponym of bird, then bird is not a hyponym of parrot. another example illustrates the transitivity: if bird is a hyperonym of parrot and parrot is a hyperonym of cockatoo, then bird is a hyperonym of cockatoo. and vice versa, if cockatoo is a hyponym of parrot and parrot is a hyponym of bird, then cockatoo is a hyponym of bird. the structure of nouns in wordnet is a cyclefree directed connected graph whose root is an abstraction that refers to all concepts included in the hierarchy and is therefore a hyperonym of all other synsets. a unique path exists between two nodes in the tree. a hyperonym may have multiple hyponyms, and a hyponym should have exactly one hyperonym. however, a common practice in wordnets is to use multiple hyperonyms. multiple hyperonyms can be exclusive (albino is either an animal or a human), conjunctive (spoon is both cutlery and container) or nonexclusive (knife can be cutlery, a weapon, or both) @xcite . disjunctive (exclusive) hyperonymy is related to polysemy in that different meanings of the same word can have different hyperonyms; thus, disjunctive multiple hyperonyms should not be present in the wordnet. actually, in wordnet, the hyperonym of albino with the meaning 'a person with congenital albinism: white hair and milky skin; eyes are usually pink' is one -person. this suggests that for an albino animal, there must be another concept in the wordnet structure that refers only to an animal with the relevant anomaly. conjunctive multiple hyperonyms have a common hyperonym (usually not the direct one). in fact, conjunctive hyperonymy exemplifies the cases in which different types of semantic relations can be defined to replace multiple hyponymy relations. the so-called non-exclusive hyperonymy allows both disjunctive and conjunctive relations, and such cases should not occur in wordnet because different senses could not be encoded in one and the same synset. for example, hatmaker defined as 'someone who makes and sells hats' has two hyperonyms: maker -'a person who makes things' and merchant -'a businessperson engaged in retail trade'. our work aims to investigate and resolve multiple hyperonymy relations in wordnet, which can be accomplished in one of two ways: either by defining new relations in place of some hyperonymy relations (since multiple hyperonymy may encompass several semantic relations that can be further specified) or by deleting hyperonymy relations (if appropriate). in our study, we define a small set of new semantic relations (such as function, origin and form) that will cover the different instances of multiple hyperonymy relations, and we classify these relations according to the defined set. the paper is organised as follows. section 2 explains the motivation behind our work. section 3 places our work in the context of related studies. section 4 presents our approach. in subsection 4.1 we show how the synsets with multiple hyperonyms were grouped automatically, such as to form semantic patterns appropriate for the next semantic analysis. we propose an updated wordnet structure that eliminates multiple hyperonymy and incorporates the newly defined relations between the respective synsets (subsection 4.2). then, in section 5, we propose a brief description of the new relations, followed by conclusions and future work (section 6). the resulting wordnet structure without multiple hyperonyms may be used for a variety of purposes that require proper inheritance. ## motivation the hyperonymy relation is exploited in many implementations related with word sense disambiguation @xcite , taxonomy extraction @xcite or ontology learning (lourdusamy and abraham, 2020; w ątróbski, 2020), knowledge mining @xcite , etc. thus, the unambiguous definition of hyperonymy is important for many language processing tasks. our motivation stems from the use of semantic classes for nouns and their inheritance from hyponyms when encoding the syntagmatic combinations of verbs and nouns. nouns and verbs are grouped in wordnet into more specific semantic classes @xcite , @xcite , describing their general meaning: noun.person, noun.animal, noun.cognition; verb.cognition, verb.change, etc. nouns are classified into twenty-five semantic classes and verbs -into fifteen semantic classes. for example, the verbs cook; fix; prepare with a definition 'prepare for eating by applying heat' can be combined with nouns classified as noun.person: the mother cooks dinner. however, not all nouns from the class noun.person can collocate with these verbs as their subject and not every noun that is not classified as a noun.person can be their object (the exspouse, ?the neoliberal, *the infant cooks dinner, ?elephant, *books). in other words, the wordnet noun semantic classes could be further specified in order to correlate precisely with the verb-noun selectional preferences. in a previous work we mapped 253 corpus pattern analysis semantic types to the appropriate wordnet noun synsets @xcite . for example, the semantic type [permission] is mapped to the synset permission 'approval to do something', the semantic type [dispute] is mapped to the synset disagreement 'the speech act of disagreeing or arguing or disputing', and so on. 55 semantic classes are employed so far in our work aiming at defining conceptual frames @xcite , and 28 new specific semantic classes are added to encode verb-noun compatibility. the mapping of hyponym synsets to the semantic class of their hyperonym is done automatically. for this purpose, eliminating multiple hyperonyms is critical for inheriting the detailed semantic classes we employ. ## related work wordnet is an inheritance (is-a) based semantic resource, although inheritance is only one of the semantic relations in the network. in wordnet, a hyponym inherits all the features of the more generic concept and adds at least one feature that distinguishes it from its superordinate and from any other hyponyms of that superordinate @xcite . in order to use the inheritance relation in wordnet, the paths along the hyperonymy -hyponymy trees should be unambiguous, or, in other words, multiple hyperonymy should be resolved where possible. inheritance is important in the way that all noun synsets that are hyponyms of a synset representing a particular semantic class should inherit the properties of this class. this is generally true, and if the inheritance relations of nouns are further specified by assigning more particular semantic classes, noun synset hierarchies can serve as sets of words eligible to fill in particular verb predicate slots. d. alan cruse proposes a three-category hyponymy model that includes natural kinds, nominal kinds, and functional kinds @xcite . natural kinds are classifications of objects such as chemical elements, biological species, and so on, for example: a dog is an animal, a violin is a musical instrument. sets of features can express the relations between natural kinds and their hyperonyms. in contrast, the relations between nominal kinds and their hyperonyms can be expressed as a single distinguishing feature: mare is a female horse, kitten is a small cat, blonde is a blond woman, and so on. functional kinds are groups of entities that are linked together by a common function, i.e., their activities and causal roles. inherent functional kinds are typical kinds of their hyperonyms, such as gun is a type of weapon, hammer is a type of tool, jacket is a type garment, and so on @xcite . the proposed distinction is used to create wordnets for languages other than english, emphasizing the distinction between natural kinds and functional kinds as taxonomic relations on the one hand, and nominal kinds as a non-taxonomic relation on the other @xcite . the inheritance properties are part of the inclusion relations, which connect a more general entity to a more specific entity. class inclusion is described as follows: x's are a type of y, x's are y's, x is a type of y, and x is a y, for example: cars are a type of vehicle; roses are a type of flower; theft is a type of crime; and employee is a person @xcite . v. storey @xcite describes several types of inclusion: classification, which relates an entity occurrence to an entity type; generalisation, in which an entity type is the union of non-overlapping subtypes; specialisation, which is defined as the inverse of generali-sation; and subset hierarchy, in which potentially overlapping subtypes exist. the inheritance principle of is-a relations states that anything that is true about the generic entity type a, must also be true of the specific entity type b. therefore, any attributes of a are also attributable to b (but not necessarily vice versa). similarly, in any relations in which a can participate, b can also participate @xcite . other authors divide inclusion into two categories: those that relate generic to generic concepts (subset and superset, generalization and specialization, a kind of, conceptual containment, role value restrictions, sets and their characteristic types) and those that relate generic to individual concepts (set membership, predication, conceptual containment, abstraction) @xcite . according to this analysis, the inclusion hierarchy of noun synsets may be divided into different hierarchies depending on the type of inclusion. our goal is not to achieve this; instead, we will concentrate on cases of multiple hyperonymy and propose changing one or more hyperonymy relations based on the semantics of the relations between the synsets. the hyponymy relation has been approached from a qualia-based perspective, yielding two types of hyponymy @xcite . briefly, the level of representation at which the semantic content of a lexical item is encoded through the properties and events that define it is referred to as the qualia structure. four fundamental qualia roles determining the lexical-semantic structure of words have been defined @xcite : it was noticed that two distinct sets of hyponyms can be distinguished: those that share the same constitutive role and those that show more specific information about this role. based on this assumption, a distinction between true taxonomic hyponymy and functional hyponymy has been proposed @xcite . hyperonymy and hyponymy in wordnet refer to the formal quale, meronymy relations -to the constitutive quale, cause relations -to the agentive quale @xcite . to systematically capture all qualia roles, the eurowordnet relations were extended with two relations @xcite : results (originates) from and has as function (goal) @xcite . the fact that the multiple hyperonymy (or multiple inheritance) relations (in many cases) encode other relations or are used to indicate something other than the conjunction of two properties has already been pointed out @xcite . so far, the investigations into multiple inheritance in wordnet have been directed mainly at validating the wordnet structure. for example, multiple inheritance test patterns were created to check and validate the semantic hierarchies of the estonian wordnet @xcite . there is general agreement that hyponymy is a complicated concept and that the relation can be separated into several relations based on the hyponym's intrinsic features and the conveyed semantic relation with the hyperonym. the presence of multiple hyperonyms indicates that the wordnet hyperonymy (and its properties) exhibits a wide range of cases. the goal of presented study is to resolve multiple hyperonymy, and we achieve it by: a) removing superfluous hyperonyms; b) replacing some inappropriate hyperonymy relations with holonymy ones; c) adding missing hyperonymy relations; and d) formulating new semantic relations to replace the multiple hyperonymy. ## description of the approach we assume that multiple conjunctive hyperonyms do not represent the same relations. in addition to hyperonymy in this case, other semantic relations are also expressed. because of the various relations, the conjunction of several hyperonyms is feasible, i.e., two or more general concepts might refer to the more specific one at the same time. we use the term true hyperonymy, or simply -hyperonymy, by which we mean a hyperonymy that expresses only the is a relation between more general and more specific concepts. in conjunctive multiple hyperonymy, one of the hyperonyms expresses the true hyperonymy relation, and the second hyperonym (and subsequent ones) express another semantic relation. following the general division of hyponyms @xcite , the properties of the qualia structure @xcite , and their application so far in the wordnet @xcite , we have identified the following three groups of relations that replace multiple hyperonyms: the following is a description of the data preparation steps that are taken before performing the multiple hyperonymy resolving procedure. ## conclusion and future work based on the hypothesis that one synset cannot be related to more than one hyperonym, other semantic relations are defined in the scope of multiple hyperonymy. tests for the identification of new relations can be formulated following the pattern of the tests for other relations. the overall conclusion is that multiple hyperonymy embraces several semantic relations which, in turn, are only partially shown within the wordnet structure. relations such as origin, form, function, etc. bear additional semantics and where they exist, they can be defined regardless of resolving multiple hyperonymy occurrences. such specification would better outline the subsets of nouns that saturate semantic preferences of a verb predicate within the semantic classes of nouns, which are propagated through the inheritance (hyperonymy) relation. we intend to use the is-a inheritance relation to subclassify the semantic classes of noun synsets to more specific groups depending on verb-noun combinability in sentences. we will demonstrate how the mapping of detailed semantic classes of nouns can benefit from a proper taxonomic tree structure.