Formal language

As explained in Natural Language Processing in Action, Second Edition

A formal language is a language defined by strict rules specifying how valid statements are composed and interpreted.

A formal language defines valid statements through strict rules for composing and interpreting symbols. Like a lock that accepts one correct sequence, it lets a machine recognize a command and produce a specific response. Mathematics, programming expressions, regular expressions, and some natural-language patterns can all use formal-language rules. section 1.4.1

Recognizing a chatbot greeting

A chatbot can match the phrase “Hello, Rosa” with a regular expression, trigger a scripted greeting, and extract useful information from the user’s statement. The same pattern-matching approach can recognize commands that unlock actions. section 1.4.1 section 1.4.2

Formal languages support several related operations:

• Define acceptable sequences with grammars, including regular grammars. section 1.4.1 section 1.4.2
• Match character sequences in search tools or user statements. section 1.4.2
• Represent processing as a finite-state machine or deterministic finite automaton. section 1.4.2

Figure 1.4 Kinds of automata

Compare how formal languages used to program finite-state automata are nested within kinds of automata. section 1.4.2

How Natural Language Processing in Action, Second Edition covers it

How deep it goes

Defines grammars, matching, extraction, and finite-state machines, while deferring detailed FSM theory and mathematics.

Examples

Uses lock sequences, chatbot greetings, search matching, grep, and pattern-based chatbot systems as concrete examples.

What you can do after

Apply it via regular expressions to match phrases, extract information, and trigger scripted responses.

How it connects

Connects formal languages with natural language, regular expressions, regular grammars, finite-state automata, and deterministic finite automata.

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Also explained in

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  Data Analysis with LLMsA formal language is a language defined by explicit symbols and grammatical rules for expressing structured statements to computational systems.

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Related concepts

• natural languagecontrasts with · Natural language is a human language that develops through social use and is used for communication, in spoken or written form.
• language modelproduced by · A language model is a computational model that represents patterns in linguistic tokens to estimate sequence probabilities and predict or generate language from context.
• regular expressionuses · A formal pattern notation that describes sets of strings and enables text to be matched, searched, extracted, or transformed.

This explainer was generated by Manning's knowledge graph from the text of Natural Language Processing in Action, Second Edition. The section links point to the parts of the book it draws on.