Syntax & Parsing
Introduction to linguistic syntax, grammar rules, and the vital role of sentence parsing in NLP algorithms.
Syntax and Sentence Parsing
Natural languages are not just random lists of words—they have highly structured hierarchical grouping rules called Syntax. A sentence's syntax determines how words group together to form logical units of meaning.
Parsing is the algorithmic process of automatically extracting this underlying syntactic structure from a stream of text data.
Syntactically Valid
"Colorless green ideas sleep furiously"
Noam Chomsky famously coined this sentence to prove that syntax is entirely separate from semantics (meaning). The sentence makes zero logical sense, but it perfectly follows English grammatical rules!
Syntactically Invalid
"Furiously sleep ideas green colorless"
This sentence contains the exact same words, but violates English syntax rules. It's un-parsable.
Why do we parse?
Parsing provides the deep structural relationship required for complex downstream tasks:
- Question Answering: It maps Who did What to Whom. Parsing tells us whether "John hit Bob" or "Bob hit John".
- Machine Translation: Different languages have different rigid syntax trees. English is Subject-Verb-Object (SVO), while Japanese is Subject-Object-Verb (SOV). You must parse the English tree to structurally map it to a Japanese tree.