advanced nlp terms

7/30/2019 Advanced NLP Terms

1/6

Advanced NLP Terms

Categorical ambiguity

More than one terminal symbol for a word

eg. "Time flies like an arrow"

There are supposed to be 5 parses for this sentence, with TIMEbeing used as a noun, verb and adjective!

Co-ordinate attachment

Co-ordinates in a sentence such as AND , OR, BUT attach two or more partstogether. This is known as co-ordinate attachment. It is a major source ofambiguity in NLP.

eg. What can you eat if you are told in the refectory "You can have peasand beans or carrots with the set meal".

- [peas] and [beans or carrots]- [peas and beans] or [carrots]

Ellipsis

part of a sentence is missingeg. Italy was beating England. Germany too.

Frames and scripts

Frames and scripts act as templates of expectation Work by Schank and others They have slots and values Slots can be

1. Compulsory

2. Optional

3. Default

4. Procedures

Global ambiguity

This means that the whole sentence can have more than 1 interpretaion.


2/6

eg. "I know more beautiful women than Pamela Anderson"

- who does more beautiful women refer to?

Grammar

Shows what structures are allowed in the language. It does this by showing how asentence can be split up into terminal symbols

eg.

sentence -> noun phrase + verb phrasenoun phrase -> nounnoun phrase -> determiner + nounverb phrase -> verb + noun phrase

Lexicon

Shows which terminal symbol a word in the language belongs toeg. eat = verbeg. duck = nouneg. duck = verb (to lower your head)

Local ambiguity

This means that part of a sentence can have more than 1 interpretaion, but not thewhole sentence.

eg. "I know more beautiful women than Pamela Anderson, although sheknows quite a lot."

- who more beautiful women refers to is not initially clear(local ambiguity) , but by the end of the sentence it is clear, so theambiguity is not global.

Non terminal symbol

A sentence sub-structure that can be broken up into either other non terminal

symbols or terminal symbolseg. noun phrase such as : the categ. verb phrase such as : ate a big fish

Parse Tree

A way to show the structure of a language fragment.eg. Cats eat fish


3/6

Parser

An algorithm that uses the grammar and lexicon to find the structure in a languagefragment (usually a sentence). The input would be the sentence (for example) andthe output would be some representation of the structure.

eg. Sue hit the mugger


4/6

Recogniser

An algorithm that uses the grammar and lexicon to test if a language fragment(usually a sentence) is valid. This means that it is described by the grammar andlexicon. The input would be the sentence (for example) and the output would be aboolean.

eg. Sue hit the mugger

True (ie. grammatical)

eg. the hit Sue mugger

False (ie. not grammatical)

Referential ambiguity

More than one object is being referred to by a noun phrase.

"Sue and Lisa gave John and Mark some grotesque horror face masks becausethey liked them."


5/6

There are supposed to be 5 parses for this sentence, with TIME being usedas a noun, verb and adjective!

Rules of discourse

Due to Grice

o Be briefo Be honesto Be relevanto Be clear

Sentence

A complete grammatical utteranceeg. Sue hit John

Structural ambiguity

More than parse for a sentence

"I saw the boy on the hill with a telescope"

Here there are no commas, no pauses in speech (probably) so we need amodel of the world to help us know where I am , and where the boy is.Are they are some distance apart? How many boys are on the hill (so weneed to differentiate between them)?

Terminal symbol

A sentence structure that cannot be split upeg. noun such as dogeg. verb such as hiteg. adjective such as green

Transition networks

They show how to traverse a sentence with allowable structures:


6/6

Word sense ambiguity

Word has one terminal symbol but can refer to different concepts

"I saw her run to the bank"

Without other sentences included in our analysis, we cannot know if it is amoney or earth bank. We might use frequency of use if we had such data.

advanced nlp terms

Documents