之前接触的NLP 知识都不系统借着学习《Introduction to Natural Language Processing》 的机会，系统的了解了解。另外可参考的课程包括：
- Natural Language Processing by Dan Jurafsky, Christopher Manning
- Natural Language Processing by Michael Collins 高级的版本
Intro
做语音识别时特别需要 IPA Chart ，这个上面也配有发音。
NLP 的难点，除了理解语法语义，歧义是其另一大难点，而歧义种类分如下几种：
- Morphological: Joe is quite impossible. Joe is quite important.
- Phonetic: Joe’s finger got number.
- Part of speech: Joe won the first round.
- Syntactic: Call Joe a taxi.
- Pp attachment: Joe ate pizza with a fork / with meatballs / with Samantha / with pleasure.
- Sense: Joe took the bar exam.
- Modality: Joe may win the lottery.
- Subjectivity: believes that stocks will rise.
- Negation: likes his pizza with no cheese and tomatoes.
- Referential: yelled at Mike. He had broken the bike. yelled at Mike. He was angry at him.
- Reflexive: John bought him a present. John bought himself a present.
- Ellipsis and parallelism: gave Mike a beer and Jeremy a glass of wine.
- Metonymy: called and left a message for Joe.
除去上面提到的问题，不标准的语言（俚语、新词等）、语法错误、字词错误、计算机解析、复杂句、幽默讽刺、指代、潜在意思等。等也是NLP 做起来比较困难的地方。
然后介绍了语言学的一些知识（ Linguistic Knowledge）：
- Phonetics and phonology - the study of sounds
- Morphology - the study of word components
- Syntax - the study of sentence and phrase structure
- Lexical semantics - the study of the meanings of words
- Compositional semantics - how to combine words
- Pragmatics - how to accomplish goals
- Discourse conventions - how to deal with units larger than utterances
接着介绍了一些语言学的知识，比如PIE 及衍生语簇及子各语支。 还有比较重要的是语音演变规则：
Grimm’sLaw
- Voiceless stops turn into voiceless fricatives
- Voiced stops become voiceless stops
Voiced aspirated stops change to voiced stops or fricatives Examples
- Ancient Greek: πούς, Latin: pēs, Sanskrit: pāda – English: foot, German: Fuß, Swedish: fot
- Ancient Greek: κύων, Latin: canis, Welsh: ci – English: hound, Dutch: hond, German: Hund
接着介绍了世界语言的几个链接：
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Original post: http://blog.josephjctang.com/2015-10/notes-of-intro-to-NLP/