Unravelling the mystery of PageRanking!

Well, to start with, there is a lot that goes into building a state-of-the-art ranking system. Mr. Larry Page, the co-founder of Google search engine says, "it [the ranking system] takes exactly what you mean and gives back exactly what you want!" (with faster response times, greater scalability, lower costs).
To understand how search engines work, let's get a brief idea of the technologies employed for the purpose:

1. Information Retrieval

It relates to querying of unstructured textual data. Information is organised into documents, documents into unstructured data. To make it clear, each HTML page is considered to be a document.
Documents have associated with them a set of keywords, and then a search is made to locate relevant documents based on user input, for example: the basis of keywords which is also called Keyword-based Information Retrieval. This type of information retrieval can be used for retrieving textual, audio and video data.

2. PageRank Technology

Even though the pages have fewer links to them, but if the links they have are much higher valued, then those pages receive a higher PageRank and are more likely to appear at the top of the search results, having greater importance and relevance. This technology is also referred to as Popularity or Prestige Ranking.

High PageRank does NOT guarantee a high search ranking for any particular term. If it did, then PR10 sites like Adobe would always show up for any search you do. They don't.

However, there are many sites such as home page servers in Universities and Web portals, that host a large number of mostly unrelated pages. For such sites, the popularity of one part of the site does not imply popularity of another part of the site. So, an alternative requires transfer of prestige(importance value) from popular pages to pages that they link to!

Google interprets a link from page A to page B as a vote. Votes cast by pages that are themselves "important" weigh more heavily and help to make other pages important. A hyperlink to a page counts as a vote of support. No links to a web page means no support for that page.

PageRank theory holds that even an imaginary surfer who is randomly clicking on links will eventually stop clicking. The probability, on any step, that he will continue is a damping factor 'd' which is generally assumed to be set around 0.85 .

An algorithm has been defined to calculate the relative relevance of a web page that is going to fulfill a user's query:

PR(A)= ((1-d)/N) + d((PR(B)/L(B)) + (PR(C)/L(C)) + ......)

where d is the damping factor, N is the number of documents in collection and L(X) is the number of links from page X.

Uses of PageRanking

1. In PageRank terms, academic departments link to each other by hiring their faculty from each other.
   
2. A Web Crawler may use PageRank to determine which URL to visit next during a crawl of the Web.
   
3. PageRank may also be used as a methodology to measure the apparent impact of a community like the Blogosphere on the overall Web itself.

3. Hypertext-matching analysis

The technology analyzes the full content of the specific page along with the neighbouring web pages to ensure that the results returned are the most relevant to the user's query.

So, the inference drawn from the aforementioned revolves around 3 major aspects:

Best locally relevant results are served globally: It is ensured that no user query is left behind.

Keeping it simple: For a wide variety of user queries, there has to be a response in multiple languages. Even then, the system has to be made simple and understandable.

No manual intervention: No editing being done manually.The final ordering of the results must be decided by the algorithms alone.

Quantum Computing

This article highlights about the revolutionary concept in computing field called the Quantum Computing. It examines the possibility of computing at the quantum level, that is at the level of atom and molecules size.

Key Objectives:

· To harness the power of atoms and molecules.

· To perform calculations billion of times faster than today’s silicon based computers.

· Quantum properties of particles can be used to represent data structure.

· Quantum mechanics can be used to perform operations with these data.

Current Technology :
· We use silicon based computers
· Information is stored in form of 0’s and 1’s
· Bit System is represented as Yes or No, True or False, High or Low.
· By the use of Optical lithography techniques, we are able to pack more transistors on a Silicon based semiconductor chip making the processors more faster every year.
· Based on Moore’s Laws (Proposed by Intel’s Co-founder Gordan Moore in 1965).

Moore’s Law :

1. Processing power (no. of transistors and speed) of computer chips was doubling every 18 months or so.

2. With the increase in processing power the size of each transistor gets reduced.

Limitations of Moore’s Law :

If Moore’s Law continues unabated, each transistor would be as small as hydrogen atom by the year 2030, where quantum nature of electrons become significant and will generate errors in computation process.

This is due to the Wave-Particle duality principle as stated by Louis De-Broglie in 1920 : “As object approaches to atomic level, it begins to show dual nature given as : λ = h/mv”

However it is possible to exploit this quantum nature to do high computation by applying quantum mechanics on computers

Definition:

A Quantum computer is any device for computation that makes direct use of distinctively quantum mechanical phenomena, such as superposition and entanglement, to perform operations on data. In a classical (silicon based) computer, the amount of data is measured by bits, but in a quantum computer, the data is measured by qubits.

The basic principle of quantum computation is that the quantum properties of particles can be used to represent and structure data, and that quantum mechanisms can be devised and built to perform operations with these data.

Bit system

Ø Yes or No
Ø True or False
Ø High or Low
Ø 1 or 0
v Includes only Boolean AND, OR and NOT function

Qubit System

Ø Shade of Yes or No
Ø Intermediate states of True or False
Ø In-between states
Ø Combination as 00, 01,10, 11
v Includes Boolean XOR, XNOR, etc.

“300 qubits can store more than 10⁹⁰ numbers simultaneously which is more than no. atoms visible in universe. This shows the power of quantum computers.”

Representation of Qubit in computers :

· Ion traps
· Nuclear magnetic resonance
· Quantum dots

Quantum Phenomenon :

· Quantum parallelism
· Quantum interference
· Quantum entanglement
· Quantum teleportation

Applications in quantum computer

· Molecular stimulation:

Quantum computer can stimulate chemical interactions allowing chemist to learn more about product interaction. Pharmaceutical research will be able to benefit a lot from this development.

· True randomness:

Quantum computers can generate random numbers with true randomness giving more accuracy in program processing

· Representing data structure:

Qubits can be used to represent data structure such as linked list in a more modified way taking less memory and process with high speed using XOR function.

· Encryption technology:

Encryption schemes currently taking million of years to guess can be checked by quantum computers within a year

· Ultra secure, super dense, communication:

Qubits can allow more information to be communicated per bit than same number of classical bits.

· Improve error correction and detection:

Recovering the information from the noisy transmission path will be faster and accurate.

Recent Developments:

· In 2005, researchers at the University of Michigan built a semiconductor chip which functioned as an ion trap. Such devices, produced by standard lithography techniques, may point the way to scalable quantum computing tools.

· On 13 February, 2007 D-Wave Systems Inc. (dwavesys.com) ran an initial demonstration of their Orion quantum computing system, which is built around a 16-qubit superconducting adiabatic quantum computer processor.

· Very recently, many researchers have begun to investigate the possibility of using quantum mechanics for hypercomputation - that is, solving undecidable problems.

Vehicle Tracking System using GPS

As it has always been a logistic nightmare to track out the vehicles on the way. In order to solve this problem of tracing out the vehicles on the way a vehicle tracking system based on Global Positioning System (GPS) has been devised. The system uses Global Positioning System as its base technology. For the communication purpose the system is set to be configured with the available terrestrial network.

Working of GPS:

The feasibility studies were started in 1960’s. The Pentagon appropriates funding for this system in 1973 and the first satellite related to this topic was launched in 1978, and the system declared fully operational in 1995.

The official name of the system was NAVSTAR GPS (Navigation Satellite Timing And Ranging Global Positioning System) and is developed by US Department of Defence. The Global Positioning System is a worldwide positioning system based on the functioning of the 29 satellites. These satellites keep transmitting the signals at a particular frequency to the earth. The GPS listeners, on earth tune to that particular frequency and listen to the signals sent by the satellite. For positioning any device which is equipped with the GPS listener, signals from three or more satellites is required. The signals from three satellites determine the latitude and longitude of the device on the earth. But the signal from four satellites determines the latitude, longitude and altitude of that device on the earth. More the signals from the satellite more will be the accuracy of the position of the device.

Use of GPS for vehicle tracking system:

For locating or tracking the vehicles, the system uses the GPS as its base technology to locate the vehicle on the earth. For this the vehicle is equipped with the GPS listener. Once the vehicle is located on the earth then the next step is to send this information to the control centre for the mapping of the vehicles. That’s here the terrestrial network comes into scene. The system uses the terrestrial network such as the available CDMA or GSM mobile network for communicating with the control center.

Once the vehicles is located then it is it sends its information such as the latitude, longitude, altitude, speed(derived), etc. to the terrestrial network. The terrestrial network then sends this information to the control center where the vehicle is mapped on the electronic map on the computer. If there is some information that is to be send to the person in the vehicle then it is sent to the terrestrial network. The terrestrial network sends this information to the device in the vehicle. For this the system use the Short Messaging Service (SMS), thus the information that is sent by the control centre to the person in the vehicle appears as SMS to him. Thus, it is fully two way communications between the control center and the device.

The location is represented by the Position Fix. A position fix is based on real – time satellite tracking and is defined by set of co-ordinates. It changes as the GPS receiver moves. Position shows the approximation of the receiver’s true location.

The path which the receiver must follow is denoted by the waypoint. A waypoint is the set of co-ordinates entered into the receiver. The position fix is matched with the waypoint within some allowed error limits. If it is within the error limits, the vehicle is following the correct path unless it is on wrong path and the control centre is sent information about this.