How to find information from Internet - Part V Search Logic - How to get the best from Search Engines

At the heart of any search endeavour, no matter what kind of search tool you are using, there are three areas that can affect your search result significantly:

  1. Content of search engine
  2. Search logic or algorithm
  3. Presentation of search result

We discussed last week how content of search engines can significantly affect your search result. This week, we look at search logic.

When confronted with a search engine, most of us type one or few words in search window and hope the search result shows most relevant information.

Now, what can you do besides typing a few relevant words into the search window ?

Well, actually a lot ! You can specify that words must be in the title of a page, or that specifying words must be in an URL, or in a special HTML tag or you can use logical operators between words like AND, OR, and NOT....

Most search engines employ keyword-based search system, that work on occurrence or non-occurrence of search word to identify relevant documents in its database. Though a few search engines have started using fuzzy logic based searches - still these are in experimental basis.

While keyword based searches are extremely powerful and ideally suited for database search - its major weakness is its inability to understand word meaning. As a result, it searches mechanically for words - leaving the problem of synonyms squarely on searcher's shoulder.

To give an example - searching for 'garment' will not get you documents dealing in 'apparel' or 'clothes' or 'T-Shirt'. Worse, the search engine may even overlook the keyword 'garments' - unless it has facility for truncation.

So, as searcher, it becomes your responsibility to construct search expression in such a way that it gets maximum relevant documents from search engine database.

Every search engine provides a set of tools for constructing efficient search expression. Perhaps the most important of all is the Boolean search operators.

What is Boolean Search ?

Boolean searching is based on a system of symbolic logic developed by George Boole, a 19th century English mathematician. Most keyword searchable computer databases support Boolean searches. Boolean search techniques may be used to perform accurate searches without producing many irrelevant documents.

When you perform a Boolean search, you search the computer database for the keywords that best describe your topic. The power of Boolean searching is based on combinations of keywords with connecting terms called operators. The three basic operators are the terms AND, OR, and NOT.


This operator combines two search words in a search expression that retrieves documents containing BOTH the words.

For example: The search expression 'Fabrics AND Buyer' will retrieve all documents that have both the words 'fabrics' and 'buyer

AND operator narrows a search. More words you combine with AND - greater will be precision in search result. However, you may also miss out relevant documents that do not contain ANY OF THE words specified.


The OR operator combines two search words in a search expression that retrieves documents containing ANY of the words.

For example, the search expression 'Agent OR Agents OR Distributor OR Distributors' will fetch all documents that have ANY of the search words.

Obviously, OR operator broadens or widens a search to include documents containing any of the search words. This operator is particularly useful when there are several common synonyms for a concept or variant spellings of a word. However, indiscriminate use of OR operator may fetch junk or unwanted documents.


NOT operator excludes unwanted documents having the specified search word. For example, the search expression 'Buyer NOT Agent' first fetches all documents that have the word Buyer then goes on to remove all documents from this collection that have the word 'agent' in it. The result is a collection of documents that have the word buyer but not the word agent.

Boolean search terms may be combined in various ways to carefully refine searches. For example:

(Buyer OR 'Buying Agent') AND (UK OR England OR Britain)

NOTE: A phrase (i.e more than one word) is always marked with inverted comma (e.g. 'Buying Agent')

This place is too short for more explanation. Interested readers may check following tutorials for graphical illustration of Boolean operators.

Related Links:

Source: FAIDA - Newsletter on Business Opportunties from India and Abroad Vol: 3, Issue 12 July 11' 2002

Author : Dr. Amit K. Chatterjee
(Amit worked in blue-chip Indian and MNCs for 15 years in various capacities like Research and Information Analysis, Market Development, MIS, R&D Information Systems etc. before starting his e-commerce venture in 1997. The views expressed in this columns are of his own. He may be reached at )

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