- Examples of Eliza

- What do these programs do right? What do they do wrong? Why?


- What makes NLP hard? (further examples)

1) Is 'book' a noun or a verb in this sentence?

I have a book on that topic.

I book my flights online.


This problem is an example of LEXICAL (word-level) ambiguity.


A possible resolution:

Often (but not always), a word preceded by a pronoun is a verb.


2) No left turn weekdays 4-6 PM except buses.

Buses can always turn?

Buses can never turn?


This appears to be a WORLD KNOWLEDGE issue, i.e. we know that
official vehicles often get special privileges.



Cf. No left turn weekdays 4-6 PM except Fridays.

This is an ATTACHMENT issue.

Attachment is a subcategory of SYNTAX (sentence structure).




3) Thank you for not smoking, eating, drinking or playing radios
   without headphones.

Thank you for not eating without headphones?

Thank you for drinking?


These are attachment issues again.

These can also be considered as WORLD KNOWLEDGE issues, i.e. we thank
people for doing helpful things and for not doing annoying things.


4) Fred's hat was blown off by the wind. He tried to catch it.

He tried to catch the hat?

He tried to catch the wind?

Pronouns often refer to the most recent noun, but not here.


5) I saw the man in the park with the telescope.

Famous attachment examples.

Can you see all 3 possibilities? In this case there are 3 syntax
trees, and each one has a different meaning.


6) I saw the Golden Gate Bridge flying into San Francisco.

Attachment issues occur in everyday text.


To what extent can an Eliza-type program work if it can't handle these
issues?