spaCy/website/docs/usage/101/_pipelines.md
Sofie Van Landeghem 0b4b4f1819 Documentation for Entity Linking (#4065)
* document token ent_kb_id

* document span kb_id

* update pipeline documentation

* prior and context weights as bool's instead

* entitylinker api documentation

* drop for both models

* finish entitylinker documentation

* small fixes

* documentation for KB

* candidate documentation

* links to api pages in code

* small fix

* frequency examples as counts for consistency

* consistent documentation about tensors returned by predict

* add entity linking to usage 101

* add entity linking infobox and KB section to 101

* entity-linking in linguistic features

* small typo corrections

* training example and docs for entity_linker

* predefined nlp and kb

* revert back to similarity encodings for simplicity (for now)

* set prior probabilities to 0 when excluded

* code clean up

* bugfix: deleting kb ID from tokens when entities were removed

* refactor train el example to use either model or vocab

* pretrain_kb example for example kb generation

* add to training docs for KB + EL example scripts

* small fixes

* error numbering

* ensure the language of vocab and nlp stay consistent across serialization

* equality with =

* avoid conflict in errors file

* add error 151

* final adjustements to the train scripts - consistency

* update of goldparse documentation

* small corrections

* push commit

* typo fix

* add candidate API to kb documentation

* update API sidebar with EntityLinker and KnowledgeBase

* remove EL from 101 docs

* remove entity linker from 101 pipelines / rephrase

* custom el model instead of existing model

* set version to 2.2 for EL functionality

* update documentation for 2 CLI scripts
2019-09-12 11:38:34 +02:00

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When you call nlp on a text, spaCy first tokenizes the text to produce a Doc object. The Doc is then processed in several different steps this is also referred to as the processing pipeline. The pipeline used by the default models consists of a tagger, a parser and an entity recognizer. Each pipeline component returns the processed Doc, which is then passed on to the next component.

The processing pipeline

  • Name: ID of the pipeline component.
  • Component: spaCy's implementation of the component.
  • Creates: Objects, attributes and properties modified and set by the component.
Name Component Creates Description
tokenizer Tokenizer Doc Segment text into tokens.
tagger Tagger Doc[i].tag Assign part-of-speech tags.
parser DependencyParser Doc[i].head, Doc[i].dep, Doc.sents, Doc.noun_chunks Assign dependency labels.
ner EntityRecognizer Doc.ents, Doc[i].ent_iob, Doc[i].ent_type Detect and label named entities.
textcat TextCategorizer Doc.cats Assign document labels.
... custom components Doc._.xxx, Token._.xxx, Span._.xxx Assign custom attributes, methods or properties.

The processing pipeline always depends on the statistical model and its capabilities. For example, a pipeline can only include an entity recognizer component if the model includes data to make predictions of entity labels. This is why each model will specify the pipeline to use in its meta data, as a simple list containing the component names:

"pipeline": ["tagger", "parser", "ner"]

import Accordion from 'components/accordion.js'

In spaCy v2.x, the statistical components like the tagger or parser are independent and don't share any data between themselves. For example, the named entity recognizer doesn't use any features set by the tagger and parser, and so on. This means that you can swap them, or remove single components from the pipeline without affecting the others.

However, custom components may depend on annotations set by other components. For example, a custom lemmatizer may need the part-of-speech tags assigned, so it'll only work if it's added after the tagger. The parser will respect pre-defined sentence boundaries, so if a previous component in the pipeline sets them, its dependency predictions may be different. Similarly, it matters if you add the EntityRuler before or after the statistical entity recognizer: if it's added before, the entity recognizer will take the existing entities into account when making predictions. The EntityLinker, which resolves named entities to knowledge base IDs, should be preceded by a pipeline component that recognizes entities such as the EntityRecognizer.

The tokenizer is a "special" component and isn't part of the regular pipeline. It also doesn't show up in nlp.pipe_names. The reason is that there can only really be one tokenizer, and while all other pipeline components take a Doc and return it, the tokenizer takes a string of text and turns it into a Doc. You can still customize the tokenizer, though. nlp.tokenizer is writable, so you can either create your own Tokenizer class from scratch, or even replace it with an entirely custom function.