nonprojectieve

Nonprojectieve is a term used in linguistics and computational linguistics to describe a type of dependency structure in which some syntactic links cross when the sentence is laid out in its linear word order. In projective structures, no two dependencies cross; nonprojectieve structures feature crossing dependencies, reflecting more flexible or complex word orders and movement phenomena.

Nonprojectieve dependencies often arise from long-distance dependencies, scrambling, topicalization, or other forward- and backward-manding processes in natural language. They are important for accurately modeling the grammar of languages that allow such phenomena and for representing certain cross-serial dependency patterns where the order of multiple dependents cannot be captured by a non-crossing tree.

In natural language processing, handling nonprojectieve structures poses extra challenges for parsing. Many classic dependency parsers assume projectivity and cannot represent crossing arcs. To address this, researchers use non-projective parsing algorithms, such as maximum spanning tree approaches or extended transition-based parsers that permit non-projective moves. Some preprocessing steps aim to projectivize sentences, trading exactness for algorithmic simplicity, while others rely on dedicated non-projective parsers to maintain linguistic fidelity.

See also projective dependency grammar and cross-serial dependencies. Nonprojectieve thus sits at the intersection of theoretical syntax and practical parsing, helping to account for the diversity of word order found across languages and the computational methods needed to analyze it.