used for Syntactic Parsing and Relation Extraction
Dependency Parsing
Dependency - an asymmetric binary relation linking two lexical items (tokens): one is the head and the other is the dependent.
- The head of a sentence (a.k.a. the root) is the main verb of the sentence; subject and object become it’s dependents.
- if a token is modifying/specifying/describing another token
- the modifying token → dependent
- the modified token → head
- Dependency structure/graph
- look for dependencies between each pair of tokens
- identify the modifier and modified token
- a link from head to token specifying the grammatical function
- Grammatical functions/dependency relation types
- this forms a directed graph G (V = tokens ,E = grammatical functions) with a linear precedence order on V
- Example (Horizontally arranged) -
- Example (Tree of tokens)
- Example (Tree of POS)
- Example (Machine Readable, using indentation)
- Example (Machine Readable, spaCy)
Alternate dependency structure parsing methods
An alternative dependency structure parsing method is via Predicate-Argument Structures (PAS) e.g. Enju Parser
whether the arguments are required depends on the token (verb). See Endocentric and exocentric constructions