spaCy/website/docs/usage/101/_architecture.md
2020-07-27 00:29:45 +02:00

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The central data structures in spaCy are the Doc and the Vocab. The Doc object owns the sequence of tokens and all their annotations. The Vocab object owns a set of look-up tables that make common information available across documents. By centralizing strings, word vectors and lexical attributes, we avoid storing multiple copies of this data. This saves memory, and ensures there's a single source of truth.

Text annotations are also designed to allow a single source of truth: the Doc object owns the data, and Span and Token are views that point into it. The Doc object is constructed by the Tokenizer, and then modified in place by the components of the pipeline. The Language object coordinates these components. It takes raw text and sends it through the pipeline, returning an annotated document. It also orchestrates training and serialization.

Library architecture

Container objects

Name Description
Doc A container for accessing linguistic annotations.
Span A slice from a Doc object.
Token An individual token — i.e. a word, punctuation symbol, whitespace, etc.
Lexeme An entry in the vocabulary. It's a word type with no context, as opposed to a word token. It therefore has no part-of-speech tag, dependency parse etc.
MorphAnalysis A morphological analysis.

Processing pipeline

Name Description
Language A text-processing pipeline. Usually you'll load this once per process as nlp and pass the instance around your application.
Tokenizer Segment text, and create Doc objects with the discovered segment boundaries.
Lemmatizer Determine the base forms of words.
Morphology Assign linguistic features like lemmas, noun case, verb tense etc. based on the word and its part-of-speech tag.
Tagger Annotate part-of-speech tags on Doc objects.
DependencyParser Annotate syntactic dependencies on Doc objects.
EntityRecognizer Annotate named entities, e.g. persons or products, on Doc objects.
TextCategorizer Assign categories or labels to Doc objects.
Matcher Match sequences of tokens, based on pattern rules, similar to regular expressions.
PhraseMatcher Match sequences of tokens based on phrases.
EntityRuler Add entity spans to the Doc using token-based rules or exact phrase matches.
Sentencizer Implement custom sentence boundary detection logic that doesn't require the dependency parse.
Other functions Automatically apply something to the Doc, e.g. to merge spans of tokens.

Other classes

Name Description
Vocab A lookup table for the vocabulary that allows you to access Lexeme objects.
StringStore Map strings to and from hash values.
Vectors Container class for vector data keyed by string.
Example Collection for training annotations.