Dependency grammar

Dependency grammar (DG) is a class of modern grammatical theories that are all based on the dependency relation (as opposed to the relation of phrase structure) and that can be traced back primarily to the work of Lucien Tesnière. Dependency is the notion that linguistic units, e.g. words, are connected to each other by directed links. The (finite) verb is taken to be the structural center of clause structure. All other syntactic units (words) are either directly or indirectly connected to the verb in terms of the directed links, which are called dependencies. DGs are distinct from phrase structure grammars, since DGs lack phrasal nodes, although they acknowledge phrases. Structure is determined by the relation between a word (a head) and its dependents. Dependency structures are flatter than phrase structures in part because they lack a finite verb phrase constituent, and they are thus well suited for the analysis of languages with free word order, such as Czech, Slovak, and Warlpiri. Dependency grammar (DG) is a class of modern grammatical theories that are all based on the dependency relation (as opposed to the relation of phrase structure) and that can be traced back primarily to the work of Lucien Tesnière. Dependency is the notion that linguistic units, e.g. words, are connected to each other by directed links. The (finite) verb is taken to be the structural center of clause structure. All other syntactic units (words) are either directly or indirectly connected to the verb in terms of the directed links, which are called dependencies. DGs are distinct from phrase structure grammars, since DGs lack phrasal nodes, although they acknowledge phrases. Structure is determined by the relation between a word (a head) and its dependents. Dependency structures are flatter than phrase structures in part because they lack a finite verb phrase constituent, and they are thus well suited for the analysis of languages with free word order, such as Czech, Slovak, and Warlpiri. The notion of dependencies between grammatical units has existed since the earliest recorded grammars, e.g. Pāṇini, and the dependency concept therefore arguably predates that of phrase structure by many centuries. Ibn Maḍāʾ, a 12th-century linguist from Córdoba, Andalusia, may have been the first grammarian to use the term dependency in the grammatical sense that we use it today. In early modern times, the dependency concept seems to have coexisted side by side with that of phrase structure, the latter having entered Latin, French, English and other grammars from the widespread study of term logic of antiquity. Dependency is also concretely present in the works of Sámuel Brassai (1800–1897), a Hungarian linguist, Franz Kern (1830-1894), a German philologist, and of Heimann Hariton Tiktin (1850–1936), a Romanian linguist. Modern dependency grammars, however, begin primarily with the work of Lucien Tesnière. Tesnière was a Frenchman, a polyglot, and a professor of linguistics at the universities in Strasbourg and Montpellier. His major work Éléments de syntaxe structurale was published posthumously in 1959 – he died in 1954. The basic approach to syntax he developed seems to have been seized upon independently by others in the 1960s and a number of other dependency-based grammars have gained prominence since those early works. DG has generated a lot of interest in Germany in both theoretical syntax and language pedagogy. In recent years, the great development surrounding dependency-based theories has come from computational linguistics and is due, in part, to the influential work that David Hays did in machine translation at the RAND Corporation in the 1950s and 1960s. Dependency-based systems are increasingly being used to parse natural language and generate tree banks. Interest in dependency grammar is growing at present, international conferences on dependency linguistics being a relatively recent development (Depling 2011, Depling 2013, Depling 2015, Depling 2017, Depling 2019). Dependency is a one-to-one correspondence: for every element (e.g. word or morph) in the sentence, there is exactly one node in the structure of that sentence that corresponds to that element. The result of this one-to-one correspondence is that dependency grammars are word (or morph) grammars. All that exist are the elements and the dependencies that connect the elements into a structure. This situation should be compared with phrase structure. Phrase structure is a one-to-one-or-more correspondence, which means that, for every element in a sentence, there is one or more nodes in the structure that correspond to that element. The result of this difference is that dependency structures are minimal compared to their phrase structure counterparts, since they tend to contain many fewer nodes. These trees illustrate two possible ways to render the dependency and phrase structure relations (see below). This dependency tree is an 'ordered' tree, i.e. it reflects actual word order. Many dependency trees abstract away from linear order and focus just on hierarchical order, which means they do not show actual word order. This constituency (= phrase structure) tree follows the conventions of bare phrase structure (BPS), whereby the words themselves are employed as the node labels. The distinction between dependency and phrase structure grammars derives in large part from the initial division of the clause. The phrase structure relation derives from an initial binary division, whereby the clause is split into a subject noun phrase (NP) and a predicate verb phrase (VP). This division is certainly present in the basic analysis of the clause that we find in the works of, for instance, Leonard Bloomfield and Noam Chomsky. Tesnière, however, argued vehemently against this binary division, preferring instead to position the verb as the root of all clause structure. Tesnière's stance was that the subject-predicate division stems from term logic and has no place in linguistics. The importance of this distinction is that if one acknowledges the initial subject-predicate division in syntax is real, then one is likely to go down the path of phrase structure grammar, while if one rejects this division, then one must consider the verb as the root of all structure, and so go down the path of dependency grammar.