> For the complete documentation index, see [llms.txt](https://finnlp.gitbook.io/fin/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://finnlp.gitbook.io/fin/in-depth-look/dependency-parser.md).

# Dependency Parser

### What is dependency parsing <a href="#what-is-dependency-parsing" id="what-is-dependency-parsing"></a>

> A natural language parser is a program that works out the grammatical structure of sentences, for instance, which groups of words go together (as "phrases") and which words are the subject or object of a verb.
>
> * *Source:* [*Stanford Natural Language Processing Group*](http://nlp.stanford.edu/software/lex-parser.shtml)

Each sentence consists of multiple tokens, and those tokens are syntactically/grammatically dependent on each other. For example a sentence like this one: `I love you` have a nominal subject `I`, a direct object `you` and a verbal phrase `love`. So the verb `love` can be said to be a parent of `I` and `you`, and since it doesn't have a parent, we describe it as the *root* of the sentence.

A little bit more elaborate example is : `The boss gave me a white pen`. This sentence also have a root `gave` and this root has children which are parents of their own children. You can imagine a visual tree-like representation of this sentence as follows:

![Dependency Parsing for "The boss gave me a white pen"](https://4151318403-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-LYkhCKGabZ1yLtwXI9o%2F-LYkqHsXjyPfkN7u7r7v%2F-LYkqellTy5RiFnuZ1Dx%2Fdep.png?alt=media\&token=d4111d7f-83a8-4cc1-99da-71c614558be1)

You can notice from the above chart that:

* `The` is a `determiner`, it's parent is `boss`.
* `Boss` is a `nominal subject`, it's parent is `gave`.
* `gave` is a `verbal phrase`, it has no parent (this it's the master of the sentence).
* `me` is a `direct object`, it's parent is `gave`.
* `a` is a `determiner`, it's parent is `pen`.
* `white` is an `adjective`, it's parent is `pen`.
* `pen` is an `indirect object`, it's parent is `gave`.

### Rules <a href="#rules" id="rules"></a>

Dependency parsing have a set of rules that every tree adheres to:

* Sentence *root* has no parents.
* Sentence *root* is usually a verb that dictates the meaning of the sentence.
* A sentence can only have one *root*.
* A token can only have one parent.
* A token can have any number of children, or no children at all.

So it really is a tree-like structure.

### Annotation Specifications <a href="#annotation-specifications" id="annotation-specifications"></a>

Each parent-child relationship has an annotation for it. Take the sentence above for example, `me` is a child of `gave` and the relationship between the two can be annotated as `DOBJ` which means **Direct Object**.

For a full list of the annotation specifications, refer to the **Dependency Parsing Annotations Specifications** article.<br>