Dependency Grammar v. Constituency Grammar
Edward Stabler, "Three Mathematical Foundations for Syntax", Annual Review of Linguistics 2019:
Three different foundational ideas can be identified in recent syntactic theory: structure from substitution classes, structure from dependencies among heads, and structure as the result of optimizing preferences. As formulated in this review, it is easy to see that these three ideas are completely independent. Each has a different mathematical foundation, each suggests a different natural connection to meaning, and each implies something different about how language acquisition could work. Since they are all well supported by the evidence, these three ideas are found in various mixtures in the prominent syntactic traditions. From this perspective, if syntax springs fundamentally from a single basic human ability, it is an ability that exploits a coincidence of a number of very different things.
The mathematical distinction between constituency (or "phrase-structure") grammars and dependency grammars is an old one. Most people in the trade view the two systems as notational variants, differing in convenience for certain kinds of operations and connections to other modes of analysis, but basically expressing the same things. That's essentially true, as I'll illustrate below in a simple example. But Stabler is also right to observe that the two formalisms focus attention on two different insights about linguistic structure. (I'll leave the third category, "optimizing preferences", for another occasion…)
This distinction has come up in two different ways for me recently. First, ling001 has gotten to the (just two) lectures on syntax, and because of the recent popularity of dependency grammar, I need to explain the difference to students with diverse backgrounds and interests, some of whom find any discussion of syntactic structure opaque. And second, someone recently asked me about whether anyone had used dependency grammar in analyzing music. (The answer seems to be "mostly not" — though see this paper — but the relevant question really is what the advantages of dependency models in this application might be.)
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