Search Engine Indexing

In order for search engines to find useful results when users carry out web searches, they have to store details of as many web pages as possible.

Indexing

In order for search engines to find useful results when users carry out web searches, they have to store details of as many web pages as possible.
Search engine indexing refers to the methods used to maintain such a database.
Search engine indexing allows results to be found efficiently.

Web crawlers

Search engines make use of software known as web crawlers, which traverse the web by visiting web pages and following the links contained on each.
The web crawlers store key information about each page in an index.
This is then used by the search engine to find results for a web user’s search.

Indexed information

The information stored may include:
- Keywords in the webpage.
- Meta tags within the code of the page.
- How recently the website is updated.

PageRank Algorithm

The PageRank algorithm is a method of ranking the web pages in a set of Google search results.

PageRank algorithm

PageRank is named after Larry Page who, along with fellow Stanford University student Sergey Brin, developed the algorithm in the mid-1990s.
- The algorithm judges how important each web page is.
The higher the score for a particular page, the closer to the top of the list of results it appears.

Operation

Google searches often contain millions of results, so PageRank is an important method of ensuring useful pages are more prominent in the list.
The algorithm has to be run constantly for each web page as the number of external links to the page can change at any time.

Algorithm

The PageRank algorithm is written as follows:
- $PR(A) = (1-d) + d \left(\frac{PR(T_1)}{C(T_1)} + ... + \frac{PR(T_n)}{C(T_n)}\right)$
Using ‘Web page A’ as an example:
- $PR(A)$ is to the PageRank of ‘Web page A’.
- $PR(T_i)$ is the PageRank of any of $n$ pages which link to ‘Web page A’.
- $C(T_i)$ is the number of outbound links on the pages which link to ‘Web page A’.
- $d$ is the damping factor, which is usually set to 0.85.

1Components of a Computer

1.1Structure & Function of the Processor

1.1.1Structure of the CPU

1.1.2Fetch, Decode, Execute Cycle

1.1.3Factors Affecting CPU Performance

1.1.4CPU Architecture

1.2Types of Processors

1.2.1CISC & RISC

1.2.2Multicore & Parallel Cores

1.3Input, Output & Storage

1.3.1Computer Systems

1.3.2Magnetic Storage

1.3.3Optical Storage

1.3.4Types of Optical Storage

1.3.5Types of Memory

1.3.6Flash Memory

1.3.7Virtual Memory

2Software & Software Development

3Exchanging Data

4Data Types, Data Structures & Algorithms

4.1Data Types

4.1.1Data Types

4.1.2Arrays & Strings

4.1.3Representing Numbers

4.1.4Binary Arithmetic

4.1.5Hexadecimal

4.1.6Converting Binary Numbers

4.1.7Floating Points in Binary

4.1.8Floating Point Arithmetic

4.1.9Bitwise Manipulation

4.1.10Character Sets

4.2Data Structures

4.2.1Arrays, Linked Lists & Queues

4.2.2Graphs, Hash Tables & Stacks

4.2.3Trees

4.3Boolean Algebra

4.3.1Computational Logic

4.3.2Boolean Logic

4.3.3Karnaugh Maps

4.3.4Boolean Identities

4.3.5Flip Flops & Adder Circuits

5Legal, Moral, Cultural & Ethical Issues

5.1Computing Related Legislation

5.1.1Data Protection Act (1998)

5.1.2Computer Misuse Act (1990)

5.1.3Copyright Designs and Patents Act (1988)

5.1.4Regulation of Investigatory Powers Act (2000)

5.2Moral & Ethical Issues

5.2.1Online Activity Tracking

5.2.2Censorship

5.2.3Cultural Issues

5.2.4Environmental Issues

5.2.5Layout, Colour Paradigms & Character Sets

6Elements of Computational Thinking

6.1Thinking Abstractly

6.1.1Abstraction

6.2Thinking Procedurally

6.2.1Decomposition

6.3Thinking Logically

6.3.1Pseudocode & Flow Diagrams

7Problem Solving & Programming

7.1Programming Techniques

7.1.1Programming Fundamentals

7.1.2Modularity

7.2Programming Construction

7.2.1Integrated Development Environments

7.2.2Testing

8Algorithms

8.1Algorithms

8.1.1Interpreting, Correcting & Completing Algorithm

8.1.2Sort Algorithms

8.1.3Insertion & Merge Sort

8.1.4Search Algorithms

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