Web Searching

WEB SEARCHING

A primary reason that people use the Web is to search for specific infirmation, including text, pictures, music and video


Types of search tools

Search engine (keyword search)	Subject directory (directory search)
Finds information related to a specific topics	Classifies Web pages in an organized set of categories

Search engine

• a program that searches documents for specified keywords and returns a list of the documents where the keywords were found.
• requires the user to enter a word or phrase, called search text or search query.
• each word of the search text is known as keyword.

Subject directory

• Classifies Web pages in an organized set of categories such as sport or shopping and related subcategories. 

• Examples of search tools:

1. AltaVista,

        2. Yahoo!,

        3. Google, 

        4. Excite

• A subject directory provides categorized lists of links arranged by subject 

• When click on the category link, the subject directory displays a list of subcategory links

• The disadvantage – users have difficulty deciding which categories to choose as the menus of links presented

https://www.google.com/search?q=subject+directory+example&tbm=isch&tbo=u&source=univ&sa=X&ved=0ahUKEwjIv-ewxOTZAhUJTbwKHSPHBm0QsAQIwAE&biw=1366&bih=662#imgrc=2A95QdwDOQtFRM:

ADVANTAGES AND DISADVANTAGES EXTRANET

advantages and disadvantages of extranet

ADVANTAGES	DISADVANTAGES
Exchange large volume of data using electronic data interchange.	Security of extranrts can be a concern when hosting valuable or propriety information.
Share product catalogs exclusively with trade.	Extranet can be expensive to implement and maintain within an organization.

ADVANTAGES AND DISADVANTANGES OF INTRANET

Advantanges and Disadvantages of Intranet

ADVANTAGES	DISADVANTAGES
Commercial or confidential data is kept secure within the organization.	High financial cost incurred by the company when initially implementing the internet.
Email remain private and may also be encrypted.	Connections between an intranet and internet potentially compromises security, by alloeing virus infection or system hacking .
High bandwidth. No connection limits unlike the internet.	Staff needs training to ensure workers know how to use the system effectively.
Reliable. The company will have dedicated IT personal to keep things running smoothly.	Information overload is another disadvantage because it reduce productivity.

Difference between LAN, MAN and WAN

CRITERIA	LAN	MAN	WAN
NETWORK SIZE	Small size (in a building)	Larger size (in a cities or campus)	Largest size (different states)
SPEED	Fastest in data transferring and acess time	slower in data transferring and access time	slowest in data transferring and access time
COST	Less costly setup and maintenance	More costly setup and maintenance	coastliest setup and maintenance
COMMUNICATION DEVICE	Connected using modems, hubs, swirch, router	connected using modem, hubs,switch,router	The connection is made via satellite communication link or via internet

NETWORK TOPOLOGY

NETWORK TOPOLOGY

Network topology is the arrangement of the various elements of a communication network.

Network topology is the topological structure of a network and may be depicted physically or logically. Physical topology is the placement of the various components of a network, including device location and cable installation, while logical topology illustrates how data flows within a network. Distances between nodes, physical interconnections, transmission rates or signal types may differ between two networks, yet their topologies may be identical.

An example is a local area network (LAN). Any given node in the LAN has one or more physical links to other devices in the network; graphically mapping these links results in a geometric shape that can be used to describe the physical topology of the network. Conversely, mapping the data flow between the components determines the logical topology of the network.

Two basic categories of network topologies exist, physical topologies and logical topologies.

The cabling layout used to link devices is the physical topology of the network. This refers to the layout of cabling, the locations of nodes, and the links between the nodes and the cabling. The physical topology of a network is determined by the capabilities of the network access devices and media, the level of control or fault tolerance desired, and the cost associated with cabling or telecommunications circuits.