partner-contact/partner_firstname/partner_view.xml

<openerp>
  <data>
    <record id="view_partner_simple_form_firstname" model="ir.ui.view">
      <field name="name">res.partner.simplified.form.firstname</field>
      <field name="model">res.partner</field>
      <field name="inherit_id" ref="base.view_partner_simple_form"/>
      <field name="arch" type="xml">
        <field name="name" position="attributes">
            <attribute name="attrs">{'readonly': [('is_company', '=', False)], 'required': [('is_company', '=', True)]}</attribute>
        </field>
        <field name="category_id" position="before">
          <group attrs="{'invisible': [('is_company', '=', True)]}">
              <field name="lastname" attrs="{'required': [('is_company', '=', False)]}"/>
            <field name="firstname" />
          </group>
        </field>
      </field>
    </record>

    <record id="view_partner_form_firstname" model="ir.ui.view">
      <field name="name">res.partner.form.firstname</field>
      <field name="model">res.partner</field>
      <field name="inherit_id" ref="base.view_partner_form"/>
      <field name="arch" type="xml">
        <field name="name" position="attributes">
            <attribute name="attrs">{'readonly': [('is_company', '=', False)], 'required': [('is_company', '=', True)]}</attribute>
        </field>
        <field name="category_id" position="before">
          <group attrs="{'invisible': [('is_company', '=', True)]}">
            <field name="lastname" attrs="{'required': [('is_company', '=', False)]}"/>
            <field name="firstname"/>
          </group>
        </field>
        <!-- Add firstname and last name in inner contact form of child_ids -->
        <xpath expr="//form[@string='Contact']/sheet/div" position="after">
           <group attrs="{'invisible': [('is_company', '=', True)]}">
            <field name="lastname" attrs="{'required': [('is_company', '=', False)]}"/>
            <field name="firstname"/>
           </group> 
        </xpath>
        <xpath expr="//form[@string='Contact']/sheet/div/h1" position="after">
           <field name="is_company" on_change="onchange_type(is_company)" class="oe_inline"/>
           <label for="is_company" string="Is a Company?"/>)
        </xpath>


      </field>
    </record>

  </data>
</openerp>