Are crossing dependencies really scarce?

Abstract

The syntactic structure of a sentence can be modelled as a tree, where vertices correspond to words and edges indicate syntactic dependencies. It has been claimed recurrently that the number of edge crossings in real sentences is small. However, a baseline or null hypothesis has been lacking. Here we quantify the amount of crossings of real sentences and compare it to the predictions of a series of baselines. We conclude that crossings are really scarce in real sentences. Their scarcity is unexpected by the hubiness of the trees. Indeed, real sentences are close to linear trees, where the potential number of crossings is maximized.

References in corpus (7)

• The spatial structure of networks
• On the uniform generation of random graphs with prescribed degree sequences
• The scarcity of crossing dependencies: a direct outcome of a specific constraint?
• A stronger null hypothesis for crossing dependencies
• Non-crossing dependencies: least effort, not grammar
• Crossings as a side effect of dependency lengths
• The scaling of the minimum sum of edge lengths in uniformly random trees

Cited by in corpus (12)

• The scarcity of crossing dependencies: a direct outcome of a specific constraint?
• Anti dependency distance minimization in short sequences. A graph theoretic approach
• Memory limitations are hidden in grammar
• The sum of edge lengths in random linear arrangements
• Bounds of the sum of edge lengths in linear arrangements of trees
• On the relation between dependency distance, crossing dependencies, and parsing. Comment on "Dependency distance: a new perspective on syntactic patterns in natural languages" by Haitao Liu et al
• Edge crossings in random linear arrangements
• The expected sum of edge lengths in planar linearizations of trees. Theory and applications
• The Impact of Edge Displacement Vaserstein Distance on UD Parsing Performance
• Who is the root in a syntactic dependency structure?
• Reappraising the distribution of the number of edge crossings of graphs on a sphere
• Formal Constraints on Dependency Syntax