Department of Computing

COMP348 Document Processing and the Semantic Web

Practical, Week 8

If you run out of time, attempt at least the exercises marked in boldface.

Part-of-Speech Tagging

There is an NLTK tutorial for PoS tagging.

1. Read Sections 4.1 and 4.2 as a complement to discussion in lectures on the concept.

2. Do exercise 2 of section 4.2.5.

3. Read Section 4.3. Try out the regular expression tagger of Section 4.3.2 on some sentences.

4. Do exercises 5 and 6 from Section 4.3.3.

5. Read Section 4.4.

Parsing

The NLTK toolkit contains a tutorial on parsing and a tutorial on chart parsing.

1. Read Section 8.5 (you may skip 8.5.3). Examine the behaviour of the shift-reduce parser (a bottom-up parser) and the recursive descent parser (a top-down parser) by calling the demos.

2. Based on the examples of context-free grammars that we have seen in the lectures and in the tutorials, write a small context-free grammar and lexicon. In particular, write a grammar that will cover the following sentences:

   1. He is a lazy man.
   2. The very tall man stopped the car.
   3. All rhododendrons are red.

3. Parse the sentences with the shift-reduce parser, the recursive descent parser, and the chart parser (bottom-up approach). Use the trace mechanism to compare the process of parsing using each method.