The position of prepositional phrases in Russian

A problem frequently encountered in the automatic parsing of Russian texts is the correct structuring of prepositional phrases in sentences. Studies of text samples indicate that, when other criteria are absent, the syntactic governors of prepositions can be determined with a high degree of accuracy by reference to the relative position and part-of-speech of elements in the clausal environment. One of the primary goals of computational linguistics is the development of automatic parsing programs for use in processing written texts. There is an enormous utility for computer programs that will produce structural descriptions of sentences comparable to the descriptions produced by humans. Although both products are admittedly imperfect, given the present inadequacies of grammatical theory, the information generated in the course of automatic syntactic analysis is of immediate use in language study: the parsing programs themselves can be improved, and a "data base" is provided for testing the theoretical principles underlying the program. The parsing routine is a research tool for the automatic assembling of facts about the combinatorial properties of sentence elements; in particular, it is a means of achieving specificity in syntactic description. (In addition, automatic parsing has practical applications in such activities as machine translation, indexing, and abstracting.) A parsing program must be based on a model of language, however imperfect and tentative that model may be. The program described in the present paper is based on a simple dependency grammar, adopted for linguistic research in Russian at The RAND Corporation. 1 In this model, the structure of a sentence is conceived as a tree-like set of relations among the words in the sentence. One word in every clause is said to be independent (in our convention, the predicate); except for this item, every other word in the clause "depends" on one and only one other word. (Double dependency is allowable in special instances, e.g., with relative pronouns .) The word on which a word depends is said to be its "governor"; the latter term is vised merely as a complement to "dependent," and does not necessarily correspond to the usage of the term in traditional grammatical description. The syntactic relationships designated here by dependency include instances of agreement and government (normally characterized by flexion in Russian), and complementation or modification of meaning. This model results in unique parsings for most sentences, assuming the acceptance of certain conventions. The latter are useful when the dependency of a …