purchase_view.xml

<?xml version="1.0" encoding="UTF-8"?>
<openerp>
    <data>
        <record id="purchase_order_form_ext" model="ir.ui.view">
            <field name="name">purchase.order.form.ext</field>
            <field name="model">purchase.order</field>
            <field name="inherit_id" ref="purchase.purchase_order_form"/>
            <field name="arch" type="xml">
                <data>
	                <field name="partner_id" position="attributes" version="7.0">					
						<attribute name="domain" >[('supplier','=',True),('is_company','=',True)]</attribute> 
					</field>
					<field name="pricelist_id" position="after" version="7.0">					
						<field name="ref_attention_id" options="{'limit': 10, 'create': false, 'create_edit': false}"/> 
					</field>
	                <field name="warehouse_id" position="after" version="7.0">
						<field name="ref_purchase_id" options="{'limit': 10, 'create': false, 'create_edit': false}"/> 
						<field name="ref_order_id" on_change="onchange_ref_order_id(ref_order_id)" options="{'limit': 10, 'create': false, 'create_edit': false}"/> 
						<field name="ref_project_name" /> 
						<field name="ref_partner_id" />
					</field>				
				</data>
			</field>
        </record>
        

        <record id="purchase_order_tree_ext" model="ir.ui.view">
            <field name="name">purchase.order.tree.ext</field>
            <field name="model">purchase.order</field>
            <field name="inherit_id" ref="purchase.purchase_order_tree"/>
            <field name="arch" type="xml">
                <data>
                    <field name="name" position="after">
                    	<field name="ref_project_name"/>
                    </field>
				</data>
			</field>
        </record>     
        
		<record id="view_purchase_order_filter_ext" model="ir.ui.view">
            <field name="name">view.purchase.order.filter.ext</field>
            <field name="model">purchase.order</field>
            <field name="inherit_id" ref="purchase.view_purchase_order_filter" />
            <field name="arch" type="xml">
                <data>
                    <xpath expr="/search/field[@name='name']" position="after">
                    	<field name="ref_project_name" string="Project"/>
                    </xpath>
                	<xpath expr="/search/group" position="inside">
                        <filter string="Project" domain="[]" context="{'group_by':'ref_project_name'}"/>
         			</xpath> 
				</data>
            </field>
        </record>        
	</data>
</openerp>