WEB SEARCHING

Web Searching : An act of looking for information in computer databases or network
⇘
  4 types: 1) Directories → web guide (hierarchical representation of hyperlinks)
                                       → enormous collection links to sites, arranged in different categories
                                       → top level = wide range of very general topics
                                       → each topic contains hyperlinks of more specialized subtopic

      * popular directories
        https://searchenginewatch.com/sew/how-to/2048976/major-search-engines-directories



                2) Search Engines → computer program that allows users to submit query that consists of
                                                   word or phrase and searches databases
                 
                3) Meta-search Engines → use of more than one other search engine to complete the search
                                                       → the results are ranked according to how well they match with
                                                            the query
                                                       → Adv : a single query can access lot of search engines
                                                            Disadv : a lot of matches will not be suitable for you
                 
                 4) Yellow Pages → allows users to lookup information about individuals
                                            → to track down telephone numbers, email addresses
                                            → contain certain information about businesses

Web Browser  : Can be defined as a soft ware application used to locate and display web

     * popular browser
http://www.techradar.com/news/software/applications/best-browser-which-should-you-be-using-932466




Searching Technique :

• Pattern Matching Queries (Fuzzy Query)

- can enter ''ungrammatical sentence'', ''incomplete sentence fragments''. ''nonsence words''

- search engines gets collection of keywords

- required keyword "+"

- prohibited keyword "-"

• Boolean Queries

- query that consists keywords but with logical operators (AND, OR, NOT)

Find a search engine that meet these conditions: - user-friendly interface

                                                                              - easy-to-understand documentation

                                                                              - convenient to access

                                                                              - a large indexed database

SEARCHING......

= user interface : allows to type a query and displays the results

= searcher : engine searches the database for matching your query 

= evaluator : engine assigns scores to the retrieved information

= gatherer : component that travels the WEB and collects information

= indexer : engine that categorizes that data collected by the gatherer

Web Resource Evaluation 

Evaluation Criteria  ⇒ Authority

                                ⇒ Accuracy

                                ⇒ Objectivity

                                ⇒ Currency

                                ⇒ Coverage

INTERNET INFRASTRUCTURE

INTERNET : Interconnected computer work by transmitting data through a special type of packet
                        switching which is known as Internet Protocol (IP).

Internet vs World Wide Web (WWW) ⇒ accessing information over the medium of the internet
     ⇓
- connects millions of computers together globally
- forming a network: any computer can communicate with any other computer

Hierarchy of Network

• From single computer to LAN
• From LAN to ISP (Internet Service Provider)
• From ISP to WWW

* ISP also known as IAP (Internet Access Provider)

* example of ISP: TM

Internet Protocol (IP Address)

- unique identifying number in every machine on the internet

- language that computers used to communicate over the internet

- normally expressed in decimal format to make easier to remember

  e.g: 216.27.61.137

 216: area or location of network (e.g: UTM)

   27: server no.

   61: division or unit no. (e.g: FP)

 137: computer no.

Domain Name System

HTTP (Hyper Text Transfer Protocol) : defines how messages are formatted and transmitted and 

                                                                    what actions Web servers and browsers should take in 

                                                                    response to various command

Type of Internet Connection and Access

• Dial Connection - used with home computers
• Cable - used a direct connection (e.g: office)
• Satellite Internet Access - required transceiver satellite to receive and transmit data
• Fixed Wireless - used in radio transmission tower (same as satellite internet)
• Broadband - transmits data digitally, modem or similar device required to translate data                                  packages
• Mobile Wireless - virtually anywhere cellular phone service available

CONNECTING A NETWORK

WIRELESS : send data through airwaves between devices, instead of physical cable
                     e.g : cellular telephone, tabs, wireless networking, satellite television, GPS units

Uses of Wireless - mobile users can access email anywhere anytime'
                            - travelers with portable computer can connect to internet through base station
                                                                                                                                     ↙                 ↘
                                                                                                                       railway station       airport
Types: 1) Wireless Wide Area Network (WWANs)
            2) Wireless Metropolitan Area Network (WMANs)
            3) Wireless Local Area Network (WLANs)
            4) Wireless Personal Area Network (WPANs)

Wireless Technology : Infrared    Bluetooth     WLANs     Broadband Wireless   WiMax    WiFi

Infrared: - send data as infrared light rays in short distance
                 - do not use signal in radio frequency

Bluetooth: - designed for very short range < 10m
                   - connect and exchange information between devices such as mobile phones, laptops,                             PCs, printers, digital cameras

WLANs: - vary from simple, independent, peer-to-peer connections between a set of PCs to more
                  complex, intra-building infrastructure networks
                - wireless solutions → point-to-point solution: bridge between two local area networks
                                                                                         : to provide alternative to cable between two                                                                                              distant locations
                                                → point-to-multi-point solution: connect several, separate location to
                                                                                                     one signal location

WiMax: - provides access to internet to fixed location with large coverage
               - speed up 70Mbps, range 30 miles
               - extent range of wireless network

Wired vs. Wireless Network

CABLING AND HARDWARE

CABLE : Medium → information moves from one device to another

1. Wired Network : physically connected using cables
                              : using conventional telephone network
2. Wireless Network : use signals to transfer data
                                  : television and radio network, cellular network

Types of Cable
(commonly used with LAN)

- Coxial Cable : have 3 layer → centre conductor : block interference
                                               → foil shield
                                               → braided shield
                         : large number of high-speed video transmission
                         : carry data quickly


- Fibre Optic Cable : centre glass core - no electronic signal
                                    e.g: UNIFI
                                  : use light to carry data or signal
                                  : have large amount of electrical interference

     

- Unshielded Twisted Pair (UTP) : 4 pair of wires = jacket
                                                         : each pair is twisted (8 wires) to eliminate interference
                                                         : disadvantage → susceptible for radio and frequency


- Shielded Twisted Pair (STP) : 2 wires wrap in foil shielded
                                                    : more reliable in data communication
                                                    : disadvantage → extra shielding can cause bulky



Cable Connector

- Coaxial Cable Connector

• Bayonet-Neill-Concelman (BNC) connector
• Adapters: T-connector, barrel connector, terminator

              

- Fiber Optic Cable Connector

•        ST & SC connector                 

          

- UTP Cable Connector

• RJ-45 connector (RJ = Registered Jack)
• look like a large telephone-style connector
• a slow allows RJ-45 to be inserted only one way

                

Topology and Cable

1. Linear/Bus → Coaxial, Twisted Pair, Fiber
2. Star ( concentrator at the middle) → Twisted Pair, Fiber
3. Star-Wired Ring → Twisted Pair
4. Tree → Coaxial, Twisted Pair, Fiber

Network Hardware/Equipment

Networking hardware includes all computers, peripherals, interface cards, and other equipment needed to perform data-processing and communication within network.

- File Server : large amount of RAM and storage space
                      : a fast network interface card

- Workstation : configured with appropriate cables, network interface card and networking software
                         : do not necessarily storage capability, files saved on file server

- Network Interface Card : physical connection between network and workstation
                                             : 3 most common network interface → Ethernet card
                                                                                                       → LocalTalk connector
                                                                                                       →Token Ring card

- Concentrator/Hubs : central connection point
                                     : lots of extra network trafic, network less efficient
                                     : for all traffic network

- Switch : can connect ethernet, toking ring and fiber channel
               : for one traffic channel

- Repeater : to boost signal
                   : can be separate device or incorporate into concentrator

- Bridges : connect multiple network segments
                 : connect different types of cabling or topology

- Routers : used to link different networks
                 : translates information from one network to another = superintelligent bridge
                 : direct signal traffic efficiently
                 : route messages between topology and cables

Network Gateway 

• Internetworking system → joining together two networks that use different base protocols.
• Can be implemented completely in software, hardware or combination of both.

COMPUTER NETWORK

Computer Network : collection of computers and other hardware devices
                                  → share hardware, software and data
                                  → communicate with each other electronically

Types of network depending on the geographical area

1. LAN (local area network) - small geographical area (home, school, etc)
                                              - file exchange, emails, printer sharing, internet

2. MAN (metropolitan area network) - city and country
                                                            - university (a group of multiple LAN)

3. WAN (wide area network) - covers large and broad geographical area
                                               - links across regional, metropolitan
                                               - consists of two or more LAN

4. PAN (personal area network) - network of personal devices (printer, mobile device, etc)
                                                    - can be wired or wireless

Network Component 

• Host/End Nodes - data source and data destination                                                                                                    - e.g: personal computer, workstation, ATM, terminal
• Transmission Media - sending electric or signal through specific media                                                                         - can be bounded (wired=fibre optic) and unbounded (wireless=satellite)
• Network Electronic Device - e.g:  bridges, routers, switches, gateways, hubs, multiplexers
• Apps/Software - can be system and operating (NOS) and (NCS=client)                                                                - control data transmission
• Network Architecture Standard and Protocol - NAS: The Blueprint of Standard                                                                                                    - e.g: TCP/IP, ethernet, Wi-Fi, WiMAX

Networking Architecture

- 2 types → client/server network

               → peer to peer network

= which are designed to communicate

1. Client/Server Network 

• client : request network resource
• server : process the request from client

- retrieve file from server : download

- transfer from client to server : upload

2. Peer to Peer Network

- no central server (e.g : bluetooth)
- direct access to other devices attached to network

• declared 'shared devices'

Network Topology : study of the arrangement or mapping of elements of network especially

                                 - physical (real)

                                 - logical topology

1. Physical

• linear bus                           
• star-wired/ring
• star
• tree/hybrid
• mesh

2. Logical

• shared media : ability to access physical layout anytime                                                                                         disadvantage → collision : two systems send information at the same time                                                         → use full-duplex to avoid collision
• token based : ring topology                                                                                                                                   disadvantage → latency (not synchronize) : delayed communication                                             advantage → no collision : use an ethernet-based net

DATA COMMUNICATION

Data is "raw data" that had been processed, arranged, stored and used to get information.

Data Communication is a process of transferring information in a form of binary between to or more devices using electronic delivery system.
⇘
transmitted via mediums - fibre optics, wires, coaxial cables or radiated electromagnetic waves (radio, infrared light, microwaves)

2 types of signal - analog signal
                           = involves 2 parameters : frequency and amplitude
       
                           - digital signal
                           = 2 possible states : 0 and 1 (language of computer)
      
Process of changing
1. analogue-digital = modulation
2. digital-analogue = demodulation

Data transmission




                         

       

3 serial transmission modes

Synchronous and Asynchronous
       
Isochronous
- Data is sent at the same time as other related data to support certain types of real time applications
- e.g: streaming voice, video, music

Directions of Data Transmission

1. Simplex - 1 way communication
                  - role of transmitter and receiver fixed
                  - e.g: radio station

2. Half-duplex - 2 directions but not at the same time
                        - one station transmits information to other without interruption
                        - e.g: walkie-talkie

3. Full-duplex - moves in both directions at the same time
                       - both stations transmit and receive simultaneously
                       - e.g: telephone

Data Compression

• using fewer bits than original representation
• all images on web are compressed, typically in the JPEG or GIF format
• examples of file compression format - ARC and ZIP