This preview shows page 1. Sign up to view the full content.
Unformatted text preview: pic.
A conventional graphical browser works as follows (see Figure 18.3): 1. The user of the web-client calls on hypertext link.
2. The browser of the web-client computer decodes the URL address of the link.
The browser contacts the server corresponding to the URL address and
requests for the object referenced by the link.
4. The server then fetches an object from the local computer and returns to the
browser a bag of bytes that contains the object.
5. The browser then inspects the bytes to determine the type of the data such as
HTML document or JPEG image, etc.
6. Finally, the browser uses the data type information to invoke the appropriate
code to manipulate and display the object on the web-client computer's screen.
Browser - User clicks on a hypertext link
Browser - Browser decodes URL address of the link
Browser - Browser requests corresponding object from the server
Browser - Browser inspects the bytes to determine the type of the data
Browser uses the data type information to invoke the appropriate code to
manipulate and display the object on the computer's screen
Network - request
Network - Reply
Server - Server fetches the object and returns to the browser a bag of bytes that
contains the object
Conventional graphical browsers that work in the manner described above are
called "first-generation" browsers. The main problem with these browsers is that
they are built in a monolithic fashion. That is, every possible type of data, protocol
and behavior that a browser can deal with is frozen into its design when the
browser is built. This means that every time a new data type, protocol, or behavior
is invented, this browser must be upgraded to make it capable of dealing with the
new situation. From the viewpoint of end users this is a difficult job because users
must continually be aware of what data types and protocols exist, which browsers
deal with which of these data types and protocols, and which versions of which
View Full Document
This document was uploaded on 04/07/2014.
- Spring '14