Augmented Grammars
Parts-of-Speech
(POS) Tagging
• Each word has a part-of-speech tag to describe its category.
• Part-of-speech tag of a word is one of major word groups (or its
subgroups).
– open classes -- noun, verb, adjective, adverb
– closed classes -- prepositions, determiners, conjuctions,
pronouns, particples
• POS Taggers try to find POS tags for the words.
•duck is a verb or noun? (morphological analyzer
cannot make decision).
• A POS tagger may make that decision by looking the surrounding
words.
– Duck! (verb)
– Duck is delicious for dinner. (noun)
Semantic Interpretation
Semantics: The meanings of the atomic symbols of the logic, and the rules for
determining the meanings of non-atomic expressions of the logic.
It specifies what facts
in the world a sentence refers to. Hence, also specifies how you
assign a truth value to a
sentence based on its meaning in the world. A fact is a
claim about the world, and may be
true or false.
There are a number of logical systems with different syntax and
semantics. We list below
a few of them.
Syntactic
Processing
• Parsing -- converting a flat input sentence into a
hierarchical structure that
corresponds to the units of meaning in the sentence.
• There are different parsing formalisms and algorithms.
• Most formalisms have two main components:
– grammar -- a declarative representation describing the
syntactic structure
of sentences in the language.
– parser -- an algorithm that analyzes the input and
outputs its structural
representation (its parse) consistent with the grammar
specification.
• CFGs are in the center of many of the parsing mechanisms. But
they are
complemented by some additional features that make the formalism
more suitable
to handle natural languages.
