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INTERNET FUNDAMENTALS. UNIT NO. - 3. WORLD WIDE WEB. INTRODUCTION. The World Wide Web (WWW), or Web for short, is a software application that makes it easy & possible for nearly anyone to publish & browse hypertext documents on the internet.
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UNIT NO. - 3 WORLD WIDE WEB
INTRODUCTION • The World Wide Web(WWW), or Web for short, is a software application that makes it easy & possible for nearly anyone to publish & browse hypertext documents on the internet. • It is called a “Web” because the interconnection between documents resemble a spider’s web. • A central idea in the development of the web is URL(uniform resource locator).
Continued.. • A URL is a webaddress that uniquely identifies a document on the web. • Such a document can be an image, an HTML file, a program etc. • Unique address make linking to anyone’s web documents possible. • The nonlinear nature of the web is one of its main attractions.
How Does the Internet Differs From WWW? • The internet is a very large group of networked computers. • The information on the web is transported over the internet. • The web therefore uses the internet.
The relationship between the web, the internet & a no. of common applications: INTERNET FTP w GOPHER WEB SMTP-eMAIL TELNET
Continued.. • Each application on the internet uses the internet as a transport mechanism. • The Web runs on HTTP protocol that is supported by the internet. • Internet supports various other protocols like FTP, Gopher etc.
Web Browser • A Web browser is one of many software applications that function as a interface between the user & the internet. • Using browser you can view web pages, read email & newsgroup. • Web browser is also called web client. • The browser sends requestto web servers to retrieve your page requests. • Browser interprets the HTML code and display the result on the screen. • Some popular web browsers are Netscape Navigator, Microsoft’s Internet explorer, Mozilla, Lynx etc..
Browser Window Terminology Different components of a browser’s window are as follows: • Title Bar: The location where the document’s title is displayed. • Menu Bar: The place showing the headings of the main pull-down command menus. • Tool Bar: The area providing access to a number of single mouse click commands. • Location: The area where the Uniform Resource Locator(URL) of the document is displayed.
Continued.. • Hot buttons: Single-click buttons that provide a no. of convenient features. • Scroll Bar: Arrows that allow the user to display a different part of a large document. • Document Area: The part of the window that is used for displaying the currently loaded document. • Status Bar: A field used to convey helpful (& current) information to the user, such as a URL or a programmer specified message. • Hyperlink: Hyperlinks are clickable text or images that generally cause the downloading and rendering of a new HTML document.
Coast-to-Coast Surfing • Web provides a means of accessing an enormous collection of information, including text, graphics, audio, video, movies, and so on. • In web you can access the information in non-linear & experimental fashion. • The non-linear approach to information gathering, or browsing, is sometimes referred to as “Surfing the Web”.
Web Terminology • Web Page: A file that can be read over the WWW. • Hyperlink • Browser • URL: A string of characters that specify the address of a web page. • Surfer: A person who spends time exploring the WWW. • Web Site: An entity on the internet that publishes web pages. • Web server: A computer that satisfies the user requests for web pages.
Uniform Resource Locator or URL A string of characters that specify the address of a web page. To go from a URL to having the Web Page displayed, the browser needs to be able to answer such questions as: • How can the page be accessed? • Where can the page be found? • What is the file name corresponding to the page?
Continued.. URL is used to resolve the above questions. URL has three parts: How://where/what For example: http://webpages.find.edu/index.html Let us break this example down into its components: a) http: Defines the protocol or scheme by which to access the page. In this case the protocol is Hypertext Transfer Protocol. This protocol is the set of rules by which an html document is transferred over the web.
Continued.. b) webpages.find.edu: Identifies the domain name of the computer where the page resides. The computer is the web server capable of satisfying the page requests. c) index.html: Provides the local name(usually a file name) uniquely identifying the specific page on the web server.
Web Page Installation • To view your webpage on Web, you will need to install them on a web server. • A Web Server is a program, located on a computer with internet access, that responds to a browser’s request for a URL.
Basic Principles for Installing a Web Page • You need to have Web pages to publish. • A Web server where the files can be placed must be available to you. • Create or copy the files into the web server after you develop & test them. • The permissions on the files need to be set so that any user anywhere can read them. Such file permissions are often referred to as “world readable”. • When someone requests your Web page, the server has to deliver it .
Bookmarks • Bookmark is a convenient feature of browsers that allows you to save the URL of any web page you display. • The saved URL is called a bookmark or favorite. • If you save the URL of a webpage, you have bookmarked the page. • A collection of bookmarks is sometimes referred to as a hotlist, list of favorites, or simply a bookmark list. • URL’s are very difficult and cumbersome to type accurately, so bookmarks are very convenient to access any webpage. • It’s a good practice to bookmark a webpage that you want to visit often.
Plug-ins and Helper Application • When a browser is designed, it can not handle every product & file format that currently exists or may exists in the future. • Browsers are huge programs, and bundling in more features makes them even larger. • Sometimes a browser is unable to handle a file format or web product, so in this case we needs to extend the browser’s capabilities.
Continued.. • For example, suppose you want to load a page & received a message such as: “no audio player installed” • This means that the webpage you loaded contains an audio component that your browser does not know how to play. • You can fix the situation by using one of two closely related mechanisms: Plug-ins & Helper applications. • Plug-ins & Helper applications do the same thing ; they extend the power of the browser.
Plug-ins • Plug-ins are tightly integrated with the browser. • We need to drag plug-ins into the browser’s plug-ins folder so that browser will find them & load them at start-up. • Plug-ins run in the browser’s window, but there are exceptions. • The browser activates the appropriate plug-in when the browser encounters a file type that it does not know how to handle. • There is a memory cost of using plug-ins. • Plug-ins can be used to play audio, show movies, run animations , work with calendars etc.. • Plug-ins launches quickly.
Helper Applications • Helper Applications are stand alone programs. • They are launched in their own window. • The helper application must be downloaded & placed in the appropriate directory. • The browser activates the appropriate helper application when the browser encounters a file type that it does not know how to handle. • There is a memory cost of using helper applications. • Helper application can be used to play audio, show movies, run animations , work with calendars etc.. • May launch slower than plug-in.
Navigator from Netscape Internet Explorer from Microsoft • Navigator is a large program. • Netscape supports table & frame tags of HTML. • Navigator usually downloaded from the web or brought from a software vendor as a stand-alone program. • Internet explorer is also a large program. • Microsoft supports marquees and a wide range of font faces. • Explorer is packaged & distributed with a variety of other microsoft products. Web Browser Comparison
Personal preferences Most browsers have a number of options that you can set: • Cookies: You can ask to be notified before a cookie is written, & you can then decide whether or not to allow the cookie to be written. • Disk cache: You can set the size of your cache. The cache stores the HTML source code & images of Web Presentations you have visited. • Fonts: You can select a font specification & also set a default font size. • Home page location: You can specify the initial page that gets loaded when the browser is first launched. • Java script & java: You can enable or disable these types of programs from running within your browser. • Messages: You can specify a default signature file or a default carbon copy address for outgoing messages.
Directories • Directory approach is one of the method of finding & organizing web information. • AWeb directory or Web guide is a hierarchical representation of hyperlinks. • The top level of the directory provides a wide range of general topics, such as, sports, arts, science, news etc.. • Each of these topics is a hyperlink that leads to more specialized subtopics. They in turn have a no. of subtopics and so on. • When traversing a directory downward, you are moving towards more specific topics. • When going upward, you are heading back to more general topics.
Continued.. • Directories are important if you want to explore a topic & its related areas or if you want to research a subject. • If you are interested in more specific topic then search engines or meta search engines are more beneficial. • Directories are easy to use, but sometimes becomes time consuming because to find a specific topic you may need to traverse 5 to 10 hyperlink levels.
Popular Directories • AOL NetFind- www.aol.com/netfind • Yahoo – www.yahoo.com • Infoseek – www.infoseek.com • Excite – www.excite.com • Lycos – www.lycos.com • CNET Search.com – www.search.com
Search Engines The second approach to organizing and locating information on the web is the search engine, which is a search program that does the following: • Allows you to submit a query that consists of a word or phrase describing the specific information you are trying to locate on web. • Searches its database to try to match your query. • Collects & returns a list of clickable URLs containing presentations that match your query. • The list is usually ordered, with the better matches appearing at the top. • Permits you to revise & resubmit a query.
Popular Search Engines • Google – www.google.com • AltaVista – altavista.digital.com • WebCrawler – www.webcrawler.com • AOL NetFind- www.aol.com/netfind • Infoseek – www.infoseek.com • Excite – www.excite.com • Lycos – www.lycos.com
Continued.. • You can see that a no. of sites provide directory, as well as search engine, capabilities; because a large database can support either mechanism. • The difference between directories & search engines is that, search engines provide direct search option.
Meta search Engine • A meta search engine or all-in-one search engine performs a search by calling more than one other search engines to do the actual work. • The results are collected & duplicateresults are eliminated. • Then the results are ranked according to how well they match your query. • The advantage of a meta search engine is that you can access a no. of different search engines with a single query.
Continued.. • The disadvantage is that a lot of matches will not be of interest to you; this means you need to spend more timeevaluating the results & deciding which hyperlink to follow. • For very specific, hard-to-locate topics, meta search engines can often be a good option.
Popular Meta Search Engine • Metasearch – www.metasearch.com • Metacrawler – www.metacrawler.com • Metafind – www.metafind.com • SavvySearch-guaraldi.cs.colostate.edu:2000
Search Terminology Here are a few common search related terms you should know about: • Search Tool: Any mechanism for locating information on the web; usually refers to a search or meta search engine, or a directory. • Query: Information entered into the search engine’s webpage that describes the information being sought. • Query Syntax: A set of rules describing what constitutes a legal query. On some search engines special symbols are used in a query. • Query Semantics: A set of rules that defines the meaning of the query. • Hit: A URL that a search engine returns in response to a query. • Match: A synonym for hit. • Relevancy score: A value that indicates how close a URL matches with a query. It is usually expressed as a value from 1 to 100, with the higher score meaning more relevant.
Pattern Matching Queries • The most basic type of query is pattern matching query. • We can make a pattern matching query by using a keyword or group of keywords. • The search engine returns the URL of any page that contains these keywords. • Some search engines returns the URL of any webpage in which the keyword occurs. • Others may return the URL of any page in which keywords appear within the first 100 words. • Still others return only the URLs of those pages in which the keywords appears in the title. • For example – “college ranking”
Boolean Queries • Boolean queries involves the boolean operations AND, OR and NOT. • A query such as : “paint AND house” will find all web pages that contains paint and house. • A query such as : “paint OR house” will find all web pages that contains either paint, house or both. • A query such as : “paint NOT house” will find all web pages that contains paint but not house.
Search Domain • Most search tools provide some flexibility in the choice of domains to search. • For example, you can search the web, newsgroups, specialized database, or the internet.
Search Subject Several search & meta search engines provide a way for you to view in real time the search queries of anonymous users. This is interesting for several reasons: • You can see how busy the search tools are. • You can see the variety of people’s interests. • You may turn up a page of personal interest that you otherwise might not have come across.
Search Strategies You can choose one of the best search engine by considering the following points: • It possesses a user-friendly interface. • It has easy-to-understand, comprehensive documentation. • Is convenient to access. • Contains a large database; so that it knows a lot about the information for which you are searching. • Does a good job in assigning relevancy score.
Search Engine Components • If you understand how a search tool works, there is a good chance you will be able to use it more effectively. • To describe how a search engine works, we split up its functions into a number of components : • User interface • Searcher • Evaluator
User Interface • The screen in which you type a query and which displays the results. • The user interface should be friendly and visually appealing. • The user should be presented with a list of hits from their search, a relevancy score for each hit, & a summary of each web page that was matched.
Searcher • Searcher is a program that searches the database to match your query. • It uses indexes to search the database. • For searching large databases sophisticated sorting & searching algorithms are implemented in the searcher.
Evaluator • Evaluator evaluates the result set of the search. • It assigns rank or relevancy score to information retrieved.
Continued.. How is the relevancy score computed by the evaluator? This varies from search engine to search engine. Some of the factors typically considered are: • How many times the words in the query appear in the page. • Whether or not the query words appear in the title. • The frequency of the query words to the beginning of the page.
