Adding new properties to a node

[sriraj paul]

Hi,

I want to add new properties to nodes.
For example : "nt:folder" type had properties like "jcr:created", 
"jcr:createdby" etc. I want to add some additional new properties to nt:folder. 

for example: Node n = session.getRootNode().addNode("test","nt:folder");
n.setProperty("Atitle", "Chasing Jackrabbit article");
 
This is giving exception : no matching property definition found for {}Atitle
 
javax.jcr.nodetype.ConstraintViolationException
It is allowing to add any property to "nt:unstructured" nodes
For example:
Node n = session.getRootNode().addNode("test");
n.setProperty("title", "Chasing Jackrabbit article");
 
will work fine.
 
How to add new properties to "nt:folder" nodetype.
 
Thank you
sriraj