Types of queries and indexing

Types of queries handled by search engine:

a>Phrase queries

b>Wild card queries

c>Boolean queries

a>Phrase queries: Queries of the form “IIM Ahmedabad” where the word order needs to maintained.

Here we can use two kind of approaches:

1>Biword Index

2>Positional Index

1>Biword Index :

>Index every consecutive pair of terms in the text as a phrase.

>For example “IIM Ahmedabad rocks”

>IIM Ahmedabad

>Ahmedabad rocks

>Disadvantage: False positives for longer queries

2>Positional Index :

>In the postings, store for each term the position(s) in which tokens of it appear:

<term, number of docs containing term;

document1: position1, position2 … ;

document2: position1, position2 … ;

etc.>

b>Wild card queries :

>List and define wildcard queries

>Identify appropriate indices for answering wildcard queries

>Trailing wildcard query

Ex: a*

>Leading wildcard query

Ex *a

c>Boolean queries:

These type of queries are usually binary type of queries.These are easily identifyable and search techniques are readily available in NLP libraries