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Lesson · Grade 6 · Applied Design, Skills and Technologies

How a Search Engine Finds and Ranks Results

  • Grade 6
  • Applied Design, Skills and Technologies
  • 1 min 14 s
  • British Columbia
  • BC6-AD-15

A made-up search engine is shown as one labelled diagram in three steps: a crawler follows links to visit five web pages, the engine builds an index of which pages have each word, and a search for "volcano eruption" is looked up in that index to find the three matching pages. The matches are put in order using two of the many ranking clues, how many of the searched words each page has and how many other pages link to it, before a reminder that the top result is not always reliable and a closing recap: crawl, index, then rank.

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In one sentence

The question this lesson answers

How are search results found, and how are they ranked?

Our made-up search engine starts with web pages joined by links.

Transcript

What the lesson says

How are search results found, and how are they ranked?

Our made-up search engine starts with web pages joined by links.

First, a program called a crawler visits pages and follows their links to find more.

Next, it makes a huge list of which pages have each word, called an index.

Now someone types volcano eruption into the search box.

The search engine looks up each word in its index, not in the whole web.

Three pages have at least one of the words: B, C and D.

Then it ranks the matches, putting them in order using many clues.

One clue is how many of your words each page has.

Another clue is how many other pages link to it.

The pages with the best scores go at the top of the results.

But the top result is not always reliable, so check it before you trust it.

A search engine crawls pages, indexes their words, then ranks the matches.

Curriculum

Where this fits

British Columbia, Grade 6

Applied Design, Skills and Technologies, Digital literacy: search techniques, how search results are selected and ranked, and criteria for evaluating search resultsBC6-AD-15

Previous: Copyright and Giving CreditNext: Can You Trust This Website? Five Checks

British Columbia, Grade 7

Applied Design, Skills and Technologies, Digital literacy: search techniques, how search results are selected and ranked, and criteria for evaluating search resultsBC7-AD-14

Previous: Copyright and Giving CreditNext: Can You Trust This Website? Five Checks

This lesson is also listed in Grade 7.

The outcomes and strands follow the British Columbia curriculum.

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