HTML and CSS Reference
In-Depth Information
13.1. An Overview of Dynamic Documents
Recall from our discussion in
Chapter 1
that the client browser initiates
data flow on the Web by contacting a server with a document request.
The server honors the request by sending the document to the client.
The client subsequently displays the document's contents to the user. For
normal web documents, a single transaction initiated from the client side
is all that is needed to collect and display the document. Once displayed,
however, it does not change.
Dynamic documents, on the other hand, are the result of multiple trans-
actions initiated from either or both the server side and the client side.
A
client-pull
document is one that initiates multiple transactions from the
client side. When the server is the instigator, the dynamic document is
known as a
server-push
document.
In a client-pull document, special HTML codes tell the client to periodic-
ally request and download another document from one or more servers
on the network, dynamically updating the display.
Server-push documents also advance the way servers communicate with
clients. Normally, over the Web, the client stays connected with a server
for only as long as it takes to retrieve a single document. With server-
push documents, the connection remains open and the server continues
to send data to the client periodically, adding to or replacing the previous
contents.
Mozilla-based browsers, including Firefox and Netscape, currently are the
only browsers able to handle HTTP server-push dynamic documents nat-
ively. And because server-push documents don't work without an HTTP
server, you can't develop and test them unless you have a server run-
ning locally as well.
13.1.1. Another Word of Caution
As always, we tell you exactly how to use these exciting but nonstandard
features, and we admonish you not to use them unless you have a com-
