Symbolic NLP

• The lexical level
  • Phonetics and Phonology - understanding how sound relates to test.
  • Orthography - understaning spelling systems.
  • Morphology - understanding how words are constructed.
  • Tokenization - splitting text into words, tokens, punctuation, etc.
    • Tokenizing by word - the smallest unit that still makes sense on its own. Allows, e.g., identification of words used often.
    • Filtering - removes words that do not contribute to meaning, e.g., "in", "is", etc.
    • Stemming and lemmatizing - reducing words to their root, e.g., "helping" and "helper" both reduce to "help".
      • Understemming - two words should be reduced to the same stem but aren't.
      • Overstemming - two unrelated words are reduced to the same stem.
    • Word-level analysis
      • Frequency - density of occurrence of words.
      • Concordance - how a word is used in an immediate context.
      • Collocations - how words are used in relation to other words.
      • Dispersion - how words are used in relation to the text.
    • Tokenizing by sentence - allows analysise of words relate to one another, e.g., negative words in a sentence.
  • Part-of-speech (POS) tagging - labeling each token with its grammatical role, e.g., noun, verb, adjective, etc.

• The syntactic level
  • Syntactic parsing - understanding sentence structure, dependencies, phrases.
  • Phrase chunking - to identify phrases, e.g., "A big fat zero".
  • Chinking - excluding patterns of text.

• The semantic level
  • Named-Entity Recognition (NER) - identifying entities, e.g., people, places, organizations, dates, etc.
  • Semantic parsing - coreferences, metaphors, ambiguity.
  • Word meaning vs. world knowledge
  • Compositional semantics (how meanings combine)

• The discourse level tasks
  • Coreference resolution - determining when different words/phrases refer to the same entity.
  • Discourse analysis - analyzing relations between sentences or paragraphs, e.g., elaboration, contrast, cause-effect, narrative coherence.
  • Dialogue coherence.
  • Pragmatics - the relationship to the intentions of the source.

• Views from Behrooz Mansouri; Diyi Yang.

Exam Style Questions