1. Text Summarization using Lexical Chains

2. Summarization using Lexical Chains Summarization? What is Summarization? Advantages… Challenges…

3. Summarization using Lexical Chains Project Goals Aim: Summary of an original text without requiring full semantic interpretation Tools: WordNet thesaurus, shallow parser, POS & Brill’s tagger, Segmentation algorithm.

4. Summarization using Lexical Chains Description Input Domain: Technical_Article.txt Processing: Algorithm by Regina Barzilay and Michael Elhadad Output: Lexical Chains & Extract

5. Summarization using Lexical Chains Design steps… Segment the original text Construct lexical chains Identify strong chains Extract significant sentences

6. Summarization using Lexical Chains Step One… Segment the original text Construct lexical chains Identify strong chains Extract significant sentences

7. Summarization using Lexical Chains Seg-ment-ation Algorithm Form a Token Sequence Parameter: w Form a Block Parameter: b Computation of Similarity Parameter: sim(b 1,b 2 )

8. Summarization using Lexical Chains …. Plot Graph. Parameter: depth score Sort Segment boundary

9. Summarization using Lexical Chains Step Two… Segment the original text Construct lexical chains Identify strong chains Extract significant sentences

10. Summarization using Lexical Chains Construction of Lexical Chains Procedure: 1. Select a set of candidate words. 2. Find appropriate chain. 3. Insert the word in the chain.

11. Summarization using Lexical Chains Step Three… Segment the original text Construct lexical chains Identify strong chains Extract significant sentences

12. Summarization using Lexical Chains Strong chains? Good predictors of strength of a chain Length = number of occurrences of members in a chain Homogeneity index = 1 – (number of distinct occurrences / length)

13. Summarization using Lexical Chains Chain Score Score(Chain) = Length * Homogeneity_Index Strength Criterion : Score(Chain) > Average(Scores) + 2* StandardDeviation(Scores)

14. Summarization using Lexical Chains Step Four… Segment the original text Construct lexical chains Identify strong chains Extract significant sentences

15. Summarization using Lexical Chains Extraction A Heuristic Select representative words Extract sentence with first appearance of representative Word.

16. Thank You