How does a search work?
Words or combinations of words that you have entered
in the search box of a search engine are compared with
the information in the search engine's database. The
searchfunction tries to match your input with the content
of this information. The documents that are found are
sorted, using a couple of algorithms, but surely on
relevance, and are presented in your browser. The most
relevant document is shown first, followed by other,
less relevant documents.
How is document
relevancy determined?
Once a search engine has found documents in
its database that relate to your input, it will list
them according to their relevance. The questions is
now, how is this relevancy determined? The algorithm,
a list of procedures and factors, is different from
company to company. Sometimes they are described on
the search engines pages, but mostly they are kept behind
the curtain.
Surely decent page content, well used meta
tags and the occurrences of your search term within
a your page count. But also external factors, like site
popularity by clickthroughs, hits of the site and nowadays
pay-per-click and pay-for-location listings play a role.
Examples of such search engines are GoTo.com
and Kanoodle.com.
How search engines
work?
The term "search engine" is often used generically
to describe both true search engines and directories.
They are not the same. The difference is how listings
are compiled.
true Search engines
True search engines such as HotBot,
create their listings automatically. They crawl the
web, and people can search through what they have found.
If you change your web pages, search engines eventually
find these changes, and that can affect how you are
listed. Page titles, body copy and other elements all
play a role.
Directories:
A directory such as Yahoo depends on humans
for its listings. You submit a short description to
the directory for your entire site, or editors write
one for sites they review. A search looks for matches
only in the descriptions submitted. Changing your web
pages has no effect on your listing. Things that are
useful for improving a listing with a search engine
have nothing to do with improving a listing in a directory.
The only exception is that a good site, with good content,
might be more likely to get reviewed than a poor site.
Hybrid search engines:
Some search engines maintain an associated
directory. Being included in a search engine's directory
is usually a combination of luck and quality. Sometimes
you can "submit" your site for review, but there is
no guarantee that it will be included. Reviewers often
keep an eye on sites submitted to announcement places,
then choose to add those that look appealing.
How are web
pages ranked?
Search for anything using your favorite search engine.
Nearly instantly, the search engine will sort through
the millions of pages it knows about and present you
with ones that match your topic. The matches will even
be ranked, so that the most relevant ones come first.
As WebCrawler founder Brian
Pinkerton puts it, "Imagine walking up to a librarian
and saying, travel. Theyre going to look at you
with a blank face." Unlike a librarian, search
engines don't have the ability to ask a few questions
to focus the search. They also can't rely on judgment
and past experience to rank web pages, in the way humans
can. Intelligent agents are moving in this direction,
but there's a long way to go.
So how do search engines go about determining
relevancy? They follow a set of rules, with the main
rules involving the location and frequency of keywords
on a web page. Call it the location/frequency method,
for short. Remember the librarian mentioned above? They
need to find books to match your request of "travel,"
so it makes sense that they first look at books with
travel in the title. search engines operate the same
way.
Pages with keywords appearing in the title
are assumed to be more relevant than others to the topic.
search engines will also check to see if the keywords
appear near the top of a web page, such as in the headline
or in the first few paragraphs of text. They assume
that any page relevant to the topic will mention those
words right from the beginning.
Frequency is the other major factor in how
search engines determine relevancy. A search engine will
analyze how often keywords appear in relation to other
words in a web page. Those with a higher frequency are
often deemed more relevant than other web pages.
Search for specific
words
Most people tend to search for "flowers"
if they are looking for a site that offers a flower
delivery service. The result is a unlimited list of
sites that offer flowers, books about flowers, flower
auctions, flower power but also flower delivery services.
Be specific in your search! If you want to find a flowers
delivery service in Paris search for "flower delivery
service in Paris". You will be surprised about
the results. Probably you will find the site of your
choice amongst the first 10 on the list.
Use
of Booleans; AND, OR, NOT
If you want to search for a term that should
be in the result entirely, you use the AND Boolean (or
the "+" sign). The term should be preceded
by the + sign, like "+flower +delivery +service
+Paris".
If you would like to search for one word
or the other word or both, use the OR Boolean in between,
like "Versailles OR Paris".
If you want to exclude a word from search,
use the NOT boolean, or use the "-" sign,
like "- Versailles +Paris".
Lowercase / Uppercase
Always enter your words in lowercase, unless you are
searching for a person, city or a country, like "+philosophy
+Nietzsche" or "+cinema +Singapore".
The use of quotes and the
asterix
If you require to look for an EXACT term,
enclose a phrase of 2 or more words with quotation marks,
like " "the phantom menace" " or " "Victoria
falls" ".
There are some search engines that offer the
possibility to search for all variants of a word by
entering a part of the word followed by an asterix "*".
if you enter "opt*" it will look for optimistic,
optimal, optics etc.
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