Web Design/Internet Essentials

Search Engines and Searching the Web

Search Engines• Search Engine Basics

• Formulating Searches

The Web and E-mail 2

Search Engine Basics• A Web search

engine is a program designed to help locate information on the Web by formulating simple keyword queries.

Search Engines• A search engine is helpful in locating information

for which you may not know the exact web address on– web pages on various topics– locating specific web pages– images – videos

• There are thousands of search engines available.

Search Engines & Types

Google Search engineLycos DirectoryAlta Vista Search engineYahoo DirectoryWebCrawler Search engineExcite Search engineMSN DirectoryAOL DirectoryHotBot Search engine

The Different Types of Search Engines

• Although the term "search engine" is often used indiscriminately to describe: – Web crawler search engines– human-powered directories– everything in between

• they are not all the same.

• Each type of "search engine" gathers and ranks listings in radically different ways.

How do search engines work

• Contains four parts – a web crawler– an indexing utility– a database– a query processor

• Web crawler: combs the web to gather data• Indexing: processes the information gather by the

crawler• then stores key terms and URL’s in a database• Query processor: allows you to access the database by

entering keyword

Web Crawler • Crawler-based search engines such as

Google, compile their listings automatically

• They "crawl" or "spider" the web, and people search through their listings

• Spiders scour the web on a regular basis.• Listings are what make up the search

engine's index or catalog• The index can be defined as a massive

electronic filing cabinet containing copies of every web page the spider finds

Directories

• Directories depend on human editors to compile their listings– Webmasters submit an address, title, and a

brief description of their site, and the submission is reviewed

• After a web site makes it into a directory it is generally very difficult to change its search engine ranking

Hybrid search engines

• Some search engines offer both crawler-based results and human compiled listings called “hybrid search engines”.

• They typically favor one type of listing.• Yahoo usually displays human-powered

listings. – It also draws secondary results from Google– which may display crawler-based results for

more ambiguous queries

Search Engine Basics

• Search engines require you to enter a word or phase, “search text” or “keyword” that describe the item you want to find

• They often respond with results that include thousands of results, whose content varies based on the information you are seeking.

Formulating Searches• Most search engines are not case sensitive

(Shift key usage not necessary)

• Search engines ignore common words like:(and, a, & the) there is no need for them.

• To search for an exact phrase, enter it in quotation marks.

• When you enter multiple terms the query processor assumes you want to see web pages that contain all of your terms.

• The asterisk (*) is referred to as the wildcard charter.

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Boolean Search• A Boolean operator is a word or symbol that

describes a relationship between keywords, – Helps you create a more focused query

Ex.1 poverty and crime Ex.2 poverty and crime and gender

Ex.3 cats not dogs Ex.4 cats or felines

Boolean Logic

Example 1: +dyslexia    +adults

Example 2: radiation    -nuclear

Key word SearchMost search engines work with keyword queries in which you enter one or more words

Ex. Mountain Bike

Search results

Open your browser and go to the website below and watch:

The Animated Internet: How Search Engines Work

http://www.learnthenet.com/ENGLISH/animate/search.html