url
DESCRIPTION
UNIFORM RESOURCE LOCATORTRANSCRIPT
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URL
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There were three question that had to be answered before a selected page could be displayed:
1. What is the page called?
2. Where is the page located?
3. How can the page be accessed?
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Each page is assigned a URL (Uniform Resource Locator) that effectively serves as the page’s worldwide name.
URL is like a sign pointing to something on the internet service tell that what type of internet service to use.
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URL have three part:
how_to_get_there://where_to_go/what_to _get the protocol The DNS name of the host Local name uniquely indicating the specific page
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For example…
http://www.cs.vu.nl/welcome.html
protocol is http
DNS name of the host www.cs.vu.nl
file name is welcome.html
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URL scheme is open-ended in the sense that it is straight forward to have protocol other than HTTP
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Name Used for Examplehttp Hypertext http://www.cs.vu.nl/ast/
ftp FTP ftp://ftp.cs.vu.nl/pub/minix/README
File Local file /user/suzanne/prog.c
News News group News:comp.os.minix
Gopher Gopher Gopher://gopher.tc.umn.edu/11/libraries
mailto Sending email mailto
telnet Remote login telnet://www.w3.org:80
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LOCATING INFORMATION IN WEB The web contain wast amout of
information,finding the right item is not so easy.
Programs that search the web are sometimes called search engines,spiders,crawlers,worms,orknowbots.
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pointer to URLS
Pointers to title String
storage
0
1
2
3
20
1
2
3
4
5 19 6
21 44
Hash code
Overflow chains
url_table heap Hash table
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HTML
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What it is…
HTML is an application of ISO standard 8879,specialized to hypertext and adapted to the web.
Very structured markup language for building web pages.
A markup language is a collection of elements, which are used to indicate structure and format of a document
Browser simply has to understand the markup commands
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HTML standards
When Mosaic was the only browser, the language it interpreted,HTML 1.0,was the de facto standard.
When new browser came along, there was a need for a formal standard, so HTML2.0 standard was produced.
HTML3.0 was initially created as a reserch effort to add many features to HTML2.0,including tables,toolbars,mathematical formulas, advanced stylesheets,and more
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A complete html element is defined by a start tag, an end tag, possible attributes and a content model
The commands inside the tags are called directives
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A proper web page consists of a head and a body enclosed by <HTML>and</HTML> tag.
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Common HTML tags Tag Description
<HTML>…</HTML> Declares the web page to be written in HTML
<HEAD>…</HEAD> Delimits the page’s head
<title>…</title> Defines the title
<body>…</body> Delimits the page’s body
<Hn>…</Hn> Delimits a level n heading
<B>…</B> Set…in boldface
<l>…</l> Set…in italics
<UL>…</UL> Brackets an unordered
<OL>…</OL> Brackets a numbered list
<MENU>…</MENU> Brackets a menu of<LI>items
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Tag Description
<LI> Start of a list item
<BR> Force a break here
<p> Start of paragraph
<HR> Horizontal rule
<PRE>…</PRE> Preformatted text; do not reformat
<IMG SRC=“ ...”> Load an image here
<A HRFE=“…”>…</A> Define a hyper link
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Forms
Forms contain boxes or buttons that allow users to fill in information or make choices and then send the information back to the page’s owner.
Using the <INPUT> tag for this purpose. Most common forms are blank fields for
accepting user text, boxes that can be checked, active maps, and submit buttons.
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Thank you