Yr 12 OCR Nationals – LEVEL 3 Unit 2 – Getting Started

It’s UNIT TWO! So what have you got in notes already? Can you even find them? QUICK QUIZ According to industry leader Search Engine Watch, only 7 percent of searchers will go beyond the third page of listings. So if you're not in the top 30 search results, you may as well not be there at all. Search engines – and how they work are important.

Search Engines Quick recap on what you should already have in notes, then moving on. Web crawlers Directories Hybrid search engines Meta search engines Children’s search engines Speciality search engines

Web crawlers A webcrawler/website crawler/ spider/ robot literally follows hyperlinks from one site to another. Argued that this keeps results in subject collections, since links are by definition, relevant to each other. Therefore it only visits pages that have references from other pages. Pages are downloaded one at a time.

Directories NOT a blinking search engine – but often thought of as such, and treated the same. Collections of human reviewed web sites arranged into topical categories. Editors check to make sure that a site is active, contains unique content, it is not under construction, and visitors can find their way around it

Hybrid search engines Well, they’re kind of a crossbreed: a search engine with a directory attached. Yahoo is the best example – although it IS a directory, it’s backup results are Google based. MSN Search also uses a crawler for backup! Amazingly, even Google also uses a directory to back up it’s results – but more later...

Meta search engines Transmits your search simultaneously to several individual search engines and their databases of web pages Best general example – but also and if you want to kick ass which must be installed, but is serious searching. Since a regular search engine canvasses no more than 30% of the Web, accessing half a dozen is more likely to cover a better range of results. Equally spammers tend to get stuffed further down the list.

Children’s search engines Pretty self-evident: searches provide ‘age- appropriate’ results Interfaces are ‘cute’ and kiddified At Ask Jeeves For Kids (ajkids below), no site that is on the CyberPatrol block list is supposed to be listed.CyberPatrol These are human vetted, so the available database is smaller, but their results are more reliable then the ‘filters’ on ‘grown up’ search engines Examples include

Speciality search engines Aimed at more depth, less breadth in results: such as answers, shopping etc Google Scholar aimed at helping...uh.. Students Range of examples at (shortened coz the full URL is too long)

QUICK QUIZ Name an example of a web crawler How are the results of a directory filtered? What are the advantages to the user of the use of bots rather than humans? What are the advantages of human filtering for the user? Name a hybrid search engine. What do you see as the potential benefits of mixing the two technologies? RETURN