When you have defined attributes on pagedefinition and you want to access it in backing bean use below code to do this:
DCBindingContainer dbc = (DCBindingContainer)this.getBindings();
AttributeBinding attr =((AttributeBinding)dbc.getControlBinding("FirstName"));
AttributeBinding email = ((AttributeBinding)dbc.getControlBinding("Email"));
System.out.println("First Name:"+attr+" "+email);