Introduction to Computional Linguistics - Suraj @ LUMS

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Oct 24, 2013 (3 years and 10 months ago)

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Introduction to

Computational Linguistics

Lecture 2

What is Computational Linguistics?


CP:

Computational Linguistics,
NLP:

Natural
Language Processing,
NLE:

Natural Language
Engineering,
HLT:

Human Language
Technology etc.


Formal definition:
CL is a discipline between
linguistics and computer science which is
concerned with the computational aspects of the
human language (Uszkreit, 2000).

Scientific and Technological
Aspects of CL


Human use natural language to communicate


Formal Theories


Linguistic Knowledge


Is linguistic information helpful for doing Natural
Language Processing?


How machines can communicate with human


CL focuses on the practical outcome of modeling human
language


The main obstacle between human and computer is
communication


Computational Linguistics develop formal models to simulate
human language technology and program them.


Linguistics Knowledge

Focusing on Words


Phonology:

sounds (cats/dogz), homophones
(bare/bear), rhythm (co`nvert, conve`rt)


Morphology:

related word forms (e.g., plural)


Syntax:

how to use the word in a sentence


Lexical Meaning:
meaning of words


Compositional Semantics:
the construction of
complex words from the meaning of the parts
(e.g., untruthfulness)

Words and Sentences Identification


String
x

is a words in a text if and only if
x

is
delimited by white space.


In order to tell whether a string is a word, look
it up in a dictionary.


String
w

is a sentence in a text if and only if w
starts with a capital letter and finishes with a
full stop.

Example


Next week, Mr. Ali will visit our department
and he is planning to provide an amount of
Rs. 12,000,000 to our bright students for
their further studies. His company ‘XYZ’
has a huge name in the field of
constructions.


Plurals (chairs’)

Major Syntactic Constitutes


Noun Phrase (NP):

referring expressions


Verb Phrase (VP):

verbs plus complements


Prepositional Phrase (PP):

direction, location etc.


Adjectival Phrase (AdjP):

complemented adjectives


Adverbial Phrase (AdvP):

modified adjectives (very
rapidly)


Complementizers (Comp):

(that, whether)

Examples


The man saw a frog with a telescope



The mouse was caught by the cat sat on
the table.

Applications


Automatic Tokenization


Automatic Part of Speech Tagger


Name Entity Recognition System


Machine Translation


Word Sense Disambiguation


Example:

River bank erosion is a growing problem.

High
-
street bank is performing well to provide financial
solutions.


Question Answering System


QED: The Edinburgh TREC
-
2003 Question Answering System.
Available at


(www.iccs.informatics.ed.ac.uk/ ~s0239229/documents/Leidner
-
etal
-
2003
-
TREC.pdf)


Query Searching (in search engines like Google)