G053 - Lecture 02Search Engines

Mr C JohnstonICT Teacher

www.computechedu.co.uk

Session Objectives Know what a search engine is and why we

need them, Know examples of common search engines, Understand how search engines create their

index, Know better methods of searching the internet

for information.

What Is A Search Engine Manual navigation of millions of web pages and thousands of newsgroups is impractical, A search engine is a catalogue of web pages, It stores details about site which searches can be carried out on, A search engine therefore is a user interface which allows you to search a huge database containing lists of web pages and

newsgroups, Search Engines comprise of three main components:

Sourcing the data Indexing and creating the database The search engine application

Sourcing Data Manual Approach

Database administrators construct the database by categorising WebPages and creating pointers to them in the database table. Very time consuming

Automated Approach Uses automated program known as a spider, robot or worm, They explore the web and automatically create search engine entries, validate links, validate HTML code and monitor what's new, They save a lot of time, however do put a burden on web-servers and can cause them to crash, Automated approach also relies on people including meta tags in their HTML code.

User Approach Where user registers his own site with each search engine by filling out a form.

Creating the Database A search engine often contains the following information about a website or

newsgroup: Title, Description (less than 50 words), Keywords, Author, When site created / updated.

Search Engine Application Main user interface is written in HTML with a box for users to enter a search string

into, When the search button is pressed the search string is processed by a computer

programming language and a search is executed on the search engine database, The results are generated and displayed in a dynamic HTML page using a mixture

of programming code and HTML.

Machine WithInternet Connection Search Engine Web server

Search Engine Request

Search Results Returned

Database Queried

Query Results

Search Engine Database

Better Searching Use phrases, not single words and enclose in quotes. Finding websites about the the Roman invasion of Britain

Roman Invasion of Britain Pages Found: 665856 Roman Pages Found: 111130 “Roman invasion of Britain” Pages Found: 114

Use + for words that must occur and — for words that must not occur. Finding websites about the Amazon Rainforest

Amazon Pages Found: 204880 Amazon –book Pages Found: 106940 +Amazon –book +rainforest Pages Found: 10905

Think about word variations and plurals. education Pages Found: 485630 educat* Pages Found: 3484050(educational, educator, educated & education will appear)

Selection of Search Engines

There are a number of different search engines available – some better than others! Most allow you to carry out searches using the tips on the last slide, others however are more intelligent and you just enter a question

and the engine attempts to answer it, Below is a list of common search engine:

www.google.co.uk www.yahoo.co.uk www.msn.co.uk www.ask.co.uk www.lycos.co.uk www.excite.co.uk

Session Task Visit the links for the further reading and read them.

They will help you complete this topics exercise. Download and complete:

SearchExercise.pub Complete Task 1 Part 1 of the assignment

Further Reading: http://www.philb.com/metatag.htm http://www.google.co.uk/help/basics.html http://www.google.co.uk/help/refinesearch.h

tml