java web app configuration question

[David Spades]

<?xml version="1.0" encoding="UTF-8"?>
<bean:beans
	xmlns:bean="http://www.springframework.org/schema/beans"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xmlns="http://www.springframework.org/schema/security"
	xsi:schemaLocation="http://www.springframework.org/schema/beans
		http://www.springframework.org/schema/beans/spring-beans-3.1.xsd
		http://www.springframework.org/schema/security
		http://www.springframework.org/schema/security/spring-security-3.1.xsd">
	
	<element>
		<second-element/>
	</element>
            
    <bean:bean id="myBean" xmlns="http://www.springframework.org/schema/beans"/>    
            
</bean:beans>

This works fine. This is some config file used to deploy a simple web app in tomcat. I got two questions :
1. if I change it to beans:bean, I would get an error warning : The prefix "beans" for element "beans:bean" is not bound. why is this?
2. why do I need to declare the namespace again? hasn't the exact namespace been declared at the top of document?
3. If I add a child element inside "second-element" I'll get compile-time error saying "second-element is not allowed to have child elements". How does this validation work? Who did the validation? tomcat? JVM? others?
4. could anyone please let me know the simple folder structure in order for the validation to work when deploying web-app in java? I mean, inside classes folder, where should the xsd be placed and where should the xml instance be put, etc.
thanks
thanks