My moudlue inherited sale.order.I try to invisible commitment_date field and change the name of requested_date field.So I used xpth for both two fields.But both of fields occurred
 
 Element '<xpath expr="//field[@name='requested_date'][not(ancestor::field)]">' cannot be located in parent view 
 Element '<xpath expr="//field[@name='commitment_date'][not(ancestor::field)]">' cannot be located in parent view 

How can I fix these error?Thank You.
Following is my code;


<?xml version="1.0" encoding="utf-8"?>
<odoo>
    <data>
        <record id="sale_order_tree_view" model="ir.ui.view">
                <field name="name">sale_order_tree_view</field>
                <field name="model">sale.order</field>
                <field name="inherit_id" ref="sale.view_quotation_tree"></field>
                <field name="arch" type="xml">                 
                  
                    <xpath expr="//field[@name='requested_date']" position="attributes">
                        <attribute name="string">CW Dates</attribute>
                    </xpath>
                    <xpath expr="//field[@name='commitment_date'][not(ancestor::field)]" position="attributes">
                        <attribute name="invisible">1</attribute>
                    </xpath>                 
                </field>
        </record>
     
    </data>
</odoo>