Deployment descriptor question

[Tontang Bei]

If I can use this as the heading in the web.xml:
"<?xml version="1.0" encoding="ISO-8859-1"?>
<!DOCTYPE web-app
PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"
"http://java.sun.com/dtd/web-app_2_3.dtd">
<web-app>"

why must I use the heading given below :
"<web-app xmlns="http://java.sun.com/xml/ns/j2ee"
xmlns:xsi="http://w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee
web-app_2_4.xsd"
version="2.4">"

[VijayKumar Sivagnanam]

"<?xml version="1.0" encoding="ISO-8859-1"?>
<!DOCTYPE web-app
PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"
"http://java.sun.com/dtd/web-app_2_3.dtd">
<web-app>"

is for Servlet version 2.3 and

"<web-app xmlns="http://java.sun.com/xml/ns/j2ee"
xmlns:xsi="http://w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee
web-app_2_4.xsd"
version="2.4">"

is for Servlet version 2.4. If you are using 2.4 compliant server, go for the latter else former.

[Manikandan Jayaraman]

Also addig to this ...

I think EL is enabled by default in 2.4, but I had to explicitly in my JSP pages when we use 2.3.

Be the latest It is good