product_view.xml

<?xml version="1.0"?>
<openerp>
  <data>

    <record model="ir.ui.view" id="product_normal_form_view">
      <field name="name">product_normal_form_view</field>
      <field name="model">product.product</field>
      <field name="inherit_id" ref="product.product_normal_form_view"/>
      <field name="arch" type="xml">
        <group name="weight" position="before">
          <group name="dimensions" string="Dimensions">
            <field name="dimensional_uom_id"/>
            <field name="length" attrs="{'readonly':[('type','=','service')]}"/>
            <field name="height" attrs="{'readonly':[('type','=','service')]}"/>
            <field name="width" attrs="{'readonly':[('type','=','service')]}"/>
          </group>
        </group>
      </field>
    </record>

    <record model="ir.ui.view" id="product_template_only_form_view">
      <field name="name">product_template_form_view</field>
      <field name="model">product.template</field>
      <field name="inherit_id" ref="product.product_template_only_form_view"/>
      <field name="arch" type="xml">
        <group name="weight" position="before">
          <group name="dimensions" string="Dimensions" attrs="{'invisible': [('product_variant_count', '&gt;', 1)]}">
            <field name="dimensional_uom_id" attrs="{'invisible': [('product_variant_count', '&gt;', 1)]}"/>
            <field name="length" attrs="{'readonly':[('type','=','service')],'invisible': [('product_variant_count', '&gt;', 1)]}"/>
            <field name="height" attrs="{'readonly':[('type','=','service')],'invisible': [('product_variant_count', '&gt;', 1)]}"/>
            <field name="width" attrs="{'readonly':[('type','=','service')],'invisible': [('product_variant_count', '&gt;', 1)]}"/>
          </group>
        </group>
      </field>
    </record>


  </data>
</openerp>