|
Search engines
work by using software known as spiders or robots to
survey the Web and build databases. Web documents, when retrieved,
are analyzed and then added to a search engine’s index.
When you log onto
a search engine site and enter a query, typing in typewriter for
example, your input is then checked against all the pages the
search engine has in its index. The pages, or Websites, that best
fit your search criteria will be displayed ranked with those with
the best match listed first.
If you want to
narrow the search, use keywords. What is a keyword,
exactly? It can simply be any word on a Webpage. For
example, I used the word “simply” in the previous sentence, making
it one of the keywords for this particular paragraph. However,
since the word “simply” has nothing to do with the subject of this
paragraph (i.e., how search engines work), it is not a very useful
keyword.
Useful keywords
and key phrases for this page, if it were a Website, would be
“search,” “search engines,” “search engine methods,” “how search
engines work,” “ranking relevancy,” “search engine tutorials,”
etc. Those keywords would actually tell a user something about
the subject and content of this article.
Unless the author
of the Web document specifies the keywords for her document it’s
up to the search engine to determine them. Essentially, this
means that search engines pull out and index words that appear to
be significant.
Since search
engines are software programs, not rational human beings, they
work according to rules established by their creators for what
words are usually
important in a broad range of documents. The title of a page, for
example, usually gives useful information about the subject of the
page (if it doesn't, it should!).
Words that are
mentioned towards the beginning of a document (think of the "topic
sentence" in a high school essay, where you lay out the subject
you intend to discuss) are given more weight by most search
engines. The same goes for words that are repeated several times
throughout the document.
Some search
engines index every word on every page. Others index only part of
the document.
Keyword searches
have a tough time distinguishing between words that are spelled
the same way, but mean something different (i.e. hard cider, a
hard stone, a hard exam, and the hard drive on your computer).
This often results in hits that are completely irrelevant to your
query.
Some search
engines also have trouble with so-called stemming—i.e., if you
enter the word “big,” should they return a hit on the word,
“bigger?” What about singular and plural words? What about verb
tenses that differ from the word you entered by only an “s,” or an
“ed”?
Search engines also cannot return hits on keywords that mean the
same, but are not actually entered in your query. A query on heart
disease would not return a document that used the word “cardiac”
instead of “heart.”
This
is just a hint at how a search engine works. Remember when
searching try to be specific.
|
