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:
-
Content of search engine
-
Search logic or algorithm
-
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.
AND
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.
OR
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
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.
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