Natural Language Processing · TEE · formulas

Thesaurus / Walker approach, with three complete examples

WSD: Lesk & Naive Bayes

Formulas explained through full worked examples

The Walker approach uses thesaurus categories as semantic evidence. Associate each candidate sense with a category. Count or weight context words that support that category. Choose the largest total.

\operatorname{score}(s)=\sum_{w\in C} I(w,\operatorname{category}(s))

$I=1$ if the supplied category mapping says the context word supports the sense, otherwise $I=0$ . The summation symbol means add all those contributions. Weighted questions may replace 1 with a supplied weight. Category membership must be supplied or justified; it is not guessed from word frequency.

Question. Disambiguate bank using Walker scoring. Context words are money, interest, annum, fetch. The finance category supports money, interest and annum; the location category supports none of these words.

Given

Two categories: Finance and Location. Each supported word contributes 1.

To find

The two totals and selected bank sense.

Formula and why it applies

Sum the category indicators for each sense.

Step 1. Make a contribution table

Word	Finance	Location
money	1	0
interest	1	0
annum	1	0
fetch	0	0

Step 2. Add Finance

$1+1+1+0=3$ .

Step 3. Add Location

$0+0+0+0=0$ .

Step 4. Select

3 > 0, so select the financial institution.

Answer. Finance, with score 3 versus 0.

Question. Use Walker scoring for “The fisherman caught bass beside the lake.” Context {fisherman,caught,lake}. The Fish category contains all three clues; the Music category contains none.

Given

Fish and Music senses, binary category membership given.

To find

The correct bass sense.

Formula and why it applies

Score = sum of context-category matches.

Step 1. Record Fish matches

fisherman → 1; caught → 1; lake → 1.

Step 2. Add Fish score

$1+1+1=3$ .

Step 3. Add Music score

$0+0+0=0$ .

Step 4. Choose

Fish has the larger score.

Answer. Bass refers to a fish.

Question. Score “The player used a bat in the match.” Context {player,match}. Sport supports both words with weights 2 and 1; Animal supports neither. Use the supplied weighted Walker scheme.

Given

Sport weights {player:2, match:1}; Animal weights {player:0, match:0}.

To find

Weighted sense scores.

Formula and why it applies

Use the sum of supplied weights, not an unweighted count, because the question explicitly gives weights.

Step 1. Sport contribution of player

Add 2.

Step 2. Sport contribution of match

Add 1. Sport total = 2 + 1 = 3.

Step 3. Animal total

0 + 0 = 0.

Step 4. Compare

3 > 0 selects the sporting implement.

Answer. Bat is the sports implement.

Walker: dictionary ke exact words nahi, context kis topic/category ko support karta hai woh count.