Lesson video

Hi, everyone.

My name is Mrs. Jenkins.

I can't wait to learn with you today.

Welcome to today's lesson taken from the unit Introduction to Computing Networks.

Today's lesson is called Selecting Search Results, and by the end of today's lesson, you'll be able to describe how search engines select results.

Before we get started, we have some key words to look at.

These words will feature throughout the lesson, so it's really important we understand what they mean before we get started.

Those words are search engine, index, and web crawler.

A search engine is a tool that finds websites based on the search term used.

So that was search engine.

An index is a big catalogue where search engines store webpage information so they can find it later.

That was index.

A web crawler is a programme that visits websites and collects information to help create a search engine's index.

So that was web crawler.

So the three we are looking for, search engine, index, and web crawler.

Keep an eye out for them throughout the lesson.

In today's lesson, selecting search results, we have two key learning cycles: identify how web crawlers create an index and how search engines use their index.

So the first one, identify how web crawlers create an index.

The internet has billions of websites.

This makes it really difficult to find what we are looking for without a search engine.

And the amount of websites has increased significantly since the world wide web was created.

So in 1991 there was one website.

Move over to 1998, there were 2 million websites, and now there is over 1 billion websites.

So that's a huge increase.

Aisha says, "I want to find out more about rabbits.

How can I find the information?" It's a great question, Aisha.

An encyclopaedia can help you.

How can you find information in an encyclopaedia? If you're searching for something in an encyclopaedia, it is best to go straight to the index.

The index is an alphabetical list of everything in the book.

It's often found at the back.

You can search it for rabbits and it would give you the page number.

This makes it much easier to find the correct page.

Using an index helps you to find information quickly and saves time.

In a similar way, search engines also use an index.

Search engines use programmes called web crawlers to create an index of the web.

The indexes are stored on a big system of computers called a data centre.

Data centres are large buildings filled with computers that store search engine indexes.

Aisha says, "But what is a web crawler?" It's a good question, Aisha.

A web crawler is a programme that visits websites and adds information about them to the search engine's index.

The web crawlers look at words on the page, links, and images.

Okay, let's have a little check-in now.

I would like you to have a look and answer: what do web crawlers create? A, a new website, B, a search engine, C, an index of websites, or D, a list of passwords.

Have a go.

How did you get on? I asked you what do web crawlers create? A, a new website, B, a search engine, C, an index of websites, or D, a list of passwords.

The answer is C.

A web crawler creates an index of websites.

Aisha's asked us again, she's got another question: "Why do search engines use web crawlers?" By using a web crawler, the search engine does not need to search the entire internet when something is typed in.

The search engine looks at the index to find the best results quickly.

Okay, let's have another check-in.

True or false: a search engine looks through every webpage on the internet when you search.

Have a go.

How did you get on? I asked you, true or false: a search engine looks through every webpage on the internet when you search.

The answer was false.

A search engine just searches its index.

We're going to move on to our first task now.

I would like you for the first part of the first task is to imagine you are a web crawler.

You are going to write five objects in the classroom and you're gonna list where the object is found.

Then you will swap your index with someone else and try to find their objects.

When you have done that, I would like you to explain how web crawlers create an index.

Have a go.

How did you get on? I asked you to firstly imagine you are a web crawler.

Write down five objects in the classroom, list where every object is found, and swap your index with someone else and try to find their objects.

The second part was to explain how web crawlers create an index.

In the first section, did having the index help you find the objects quickly? By knowing where they can be found, it should have been quite quick to find them.

And to explain how web crawlers create an index.

Web crawlers visit webpages and collect information.

They add it to a search engine's index, which helps organise websites so they can be found in searches.

Great job, everyone! We're going to move on to our second learning cycle now: how search engines use their index.

Laura asks us, "What happens when you search?" When you type a search term, the search engine looks at its index for the best matches.

It does not scan the entire internet at that moment.

Some searches return more results than others.

Some words appear a lot in the index, which means more results are shown.

If you search "dog," it'll show millions of results.

Jacob said, "But then how can I narrow down my search?" Great advice, Laura.

She has said, "Adding more words helps the search engine limit what is shown." Searching "golden retriever puppy care" gives fewer but more useful results than searching "dog." True or false: adding more words to a search can help narrow the results.

Have a go.

How did you get on? I asked you, true or false: adding more words to a search can help narrow the result.

The answer is true.

Adding more words to a search can narrow the results that we can see.

Search engines try to show the most relevant results first.

Some of the ways the results are sorted are how many times the word appears, how trusted the website is, and how recent the page is.

Most search engines display the amount of results at the top of the list of results.

This shows how refining the results can reduce the number of websites listed.

For example, searching "chocolate cake" finds 7 million results, but "searching vegan chocolate cake" finds 2 million results.

So adding those words reduces the amount of search results found.

What happens if you add more words to your search? A, you get more results, B, you get fewer but more relevant results, or C, the search engine stops working.

Have a go.

How did you get on? I asked you what happens if you add more words to your search? A, you get more results, B, you get fewer but more relevant results, C, the search engine stops working.

The answer is B.

When you add more words to your search, you get fewer but more relevant results.

Great job! We're going to move on to task B now.

I would firstly like you to fill in the blanks.

When you enter a search term, the search engine looks for matches in its blank, not across the whole internet.

If a search engine returns too many results, you can add more blank to make it more specific.

Have a go.

How did you get on? I asked you to fill in the blanks.

When you enter a search term, the search engine looks for matches in its blank, not across the whole internet.

If a search engine returns too many results, you can add more blank to make it more specific.

Let's have a look at the answers.

When you enter a search term, the search engine looks for matches in its index, not across the whole internet.

If a search engine returns too many results, you can add more words to make it more specific.

Great job! We're gonna move on to part two of this task now, and I would like you to list three ways that the search engine might sort the results.

Have a go.

How did you get on? I asked you to list three ways that the search engine might sort the results.

The three ways the search engine might sort the results are by how many times the word appears, by how trusted the website is, and by how recent the page is.

Great job, everyone! You have worked so hard today, everyone.

Well done! Let's summarise what we have learned in today's lesson.

The internet has billions of websites, so finding what you are looking for is difficult without a search engine.

Search engines use programmes called web crawlers to create an index of the web.

When you type a search term, the search engine looks at its index for the best matches.

It does not scan the entire internet at that moment.

Well done, everyone! You've worked really hard today.

I hope to learn with you again soon.