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Combining Concepts - The Importance
of Elimination
Rarely does one search for information on a single
concept. One almost always is looking for an aspect of the concept, or wishes
to find information on a combination of concepts. Let us consider the topic "Diabetes
Mellitus". It is a topic where there is simply far too much information available.
So
one may look for something like
- Drug therapy in diabetes (aspect)
-
Diagnosis of diabetes (aspect)
- Diabetes and hypertension (combination)
-
Diabetes and cancer (combination)
There are different methods of combining
concepts and usually Boolean Operators are used. The common operators (combinations)
are AND, OR and NOT. Most people use one or the other of these, but do not know
about the "additional effective uses" of the NOT operator.
EXAMPLE
A search for information on diabetes in children:
A
PubMed search yielded the following:
SEARCH
TERMS | RETRIEVAL | | Diabetes
Mellitus AND Child | 17955 | | (Diabetes
Mellitus AND Child) NOT (adult OR middle age OR aged OR aged 80 and over) | 8447
|
Why does the first combination yield so many more?
This is because there are a good number of references that deal with children
as well as adults, and these have emerged in the combination.
When
one adds to the search strategy - "NOT adult OR..." the references that deal
with a range of adult age groups are knocked off, and hence the 2464 references
that remain, deal only with children.
Please note - the words in bracket
(adult, middle age, aged, and "aged 80 and over") are standard keywords
(thesaurus terms) in the Medline database. These cover all synonyms of the adult
age group.
An Google search yielded
the following:
SEARCH
TERMS | RETRIEVAL IN GOOGLE
| | +diabetes +child | About
Web 6,000,000 pages | | +diabetes +child -adult | About
Web 3,000,000 pages | | +diabetes +child -adult - old
-aged -elderly | About Web 600,000 pages (1/10th the first!)
|
Note the same phenomenon operating here. The number has
dwindled in the second step. In the third step it has dwindled further.
Here,
we had to use words like aged, elder (or elderly), old etc, because this was a
web-based search, and we needed to use synonyms of the word adult.
Note
the difference - in a Web based search, WE (the searchers), need to think up of
a whole lot of synonyms. In a database like Medline, there are set words that
we needed to use, and these took care of all synonyms.
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