Natural Language Processing
PA153
Pavel Rychlý
18 Sep 2023
Pavel Rychlý ·Natural Language Processing ·18 Sep 2023 1 / 19
Natural Language Processing at FI
Natural Language Processing Centre
around 10 PhD students
you can be part of it (PV173 - 3 credits each semester)
bachelor/master thesis
machine translation, AVER project
Pavel Rychlý
head of NLP Centre
corpora, lexicography, machine translation
Pavel Rychlý ·Natural Language Processing ·18 Sep 2023 2 / 19
Technical information
Study materials in IS
Exam: written – max 10 questions
open books (offline)
max 60 points
30 point to pass
extra points (max 30) for homeworks, projects
find good examples, illustrations to improve understanding
code, language, pictures
exam, homeworks, ... in English, Czech, Slovak
Pavel Rychlý ·Natural Language Processing ·18 Sep 2023 3 / 19
Previous knowledge
no special requirements
reading mathematics
probabilities
examples in Python
NumPy, PyTorch (matrix operations)
complements
IB030: Introduction to Computer-based Natural Language Processing
IB047: Introduction to Corpus Linguistics and Computer Lexicography
PV021: Neural Networks
IA161: Natural Language Processing in Practice
Pavel Rychlý ·Natural Language Processing ·18 Sep 2023 4 / 19
Terminological remark
Used terms:
Quantitative and statistical linguistics
Algebraic linguistics (N. Chomsky)
Mathematical linguistics
computational (počítačová, komputační) linguistics
Today Natural Language processing (ZPJ, NLP)
Human language technology (HLT)
speech processing (ASR, TTS)
Pavel Rychlý ·Natural Language Processing ·18 Sep 2023 5 / 19
Natural language (NL)
Czech, English
not formal languages (programming)
1000s different languages, sub-languages
two different modalities
text: sentences, documents
speech: utterances, speakers
Pavel Rychlý ·Natural Language Processing ·18 Sep 2023 6 / 19
Motivation
Why to pay attention to natural language?
Language behaviour represents one of the fundamental aspects of
human behaviour.
NL is an essential component of our life as a main tool of
communication.
In NL we express and record our knowledge, scientific findings, world
understanding.
Language texts serve as a memory of mankind for knowledge transfer
between generations.
NL is a base for human-computer communication.
We want to know how ChapGPT works!
Pavel Rychlý ·Natural Language Processing ·18 Sep 2023 7 / 19
NLP – applications: MT
Machine translation – testbed for NLP theory
Georgetown–IBM experiment (1954) – demonstration
ALPAC report (1966)
Google Translator – first widely used
Deep learning brings higher quality
Human quality in many areas
more in PV061 (Machine Translation)
Pavel Rychlý ·Natural Language Processing ·18 Sep 2023 8 / 19
NLP – applications: Text
Text processing – spell checkers, grammar and style checkers
Hyphenation, DTP
Fulltext search (lemmatizaion, stemming)
Semantic web – intelligent searching, exploiting metadata
Information extraction
Summarization
Pavel Rychlý ·Natural Language Processing ·18 Sep 2023 9 / 19
NLP – applications: Speech
Speech communication with computers (robots)
Synthesis – Text to speech systems
Automatic speech recogition (ASR), dictating machines, smart phones
Applications at courts, in Parliament, in medicine
Can we have a chat with our computer? See PEPPER!
Pavel Rychlý ·Natural Language Processing ·18 Sep 2023 10 / 19
NLP – applications: AI
Expert systems – e.g. Mycin (diagnostics in medicine)
Dialogue and question-answering (QA) systems
Turing test (Eliza, Loebner Prize)
NL understanding in general, stories and messages
Robotic applications – SHRDLU, 1971 (T. Winograd), the first system
containing knowledge, inference and grammar
Ontologies, semantic networks (WordNet)
Robotic family NAO, PEPPER, ROMEO (Softbank)
more in PV277 (Programming Applications for Social Robots)
Pavel Rychlý ·Natural Language Processing ·18 Sep 2023 11 / 19
Problems with NLP
Zipf‘s law
high number of low frequent items (words, phrases, ...)
Ambiguity
meaning depends on context
Variability
languages evolve
new words/phrases
transfer from other areas
Pavel Rychlý ·Natural Language Processing ·18 Sep 2023 12 / 19
Problems: Zipf‘s law
rank-frequency plot
highly skewed distribution
Pavel Rychlý ·Natural Language Processing ·18 Sep 2023 13 / 19
Problems: Ambiguity
Many components in a natural language are ambiguous
word meaning (band)
wordforms (he runs, my runs)
basic form (lemma)
part of speech, morphological categories
characters ( I, L), different scripts
names
formal languages: unique identifiers
Pavel Rychlý ·Natural Language Processing ·18 Sep 2023 14 / 19
Problems: Variability
languages evolve
old books are hard to read
different orthography, syntax, meaning
new words/phrases
mobile phone
Barbenheimer (wikipedia page in 24 languages)
transfer from other areas
language is a live organism
Pavel Rychlý ·Natural Language Processing ·18 Sep 2023 15 / 19
Approaches to NLP
symbolic
rules from experts
no data
statistical
structure/model from experts
optimization of parameters from data
some data
neural (deep learning)
everything from data
huge amount of data
usually a combination
Pavel Rychlý ·Natural Language Processing ·18 Sep 2023 16 / 19
Example: sentence boundaries
Find rules to detect sentence boundaries.
English: regular expression: [.!?]
Is is good enough?
Does it work in other languages?
Is [.!?] [A-Z] better?
Pavel Rychlý ·Natural Language Processing ·18 Sep 2023 17 / 19
Levels of language analysis
Phonetics and phonology, speech signal
Morphology – flection (and word formation)
Syntax – constituent, dependency
Semantics – lexical, logical
Pragmatics – relations of users to the language expressions
Discourse, anaphorical relations, reference
Pavel Rychlý ·Natural Language Processing ·18 Sep 2023 18 / 19
Summary
Problems with NLP
Zipf‘s law
Ambiguity
Variability
Approaches
symbolic (rule-based)
statistical
neural (deep learning)
Pavel Rychlý ·Natural Language Processing ·18 Sep 2023 19 / 19