website_sale_add_curve/view/product_view.xml

<?xml version="1.0" encoding="UTF-8"?>
<openerp>
  <data>
    <record id="view_product_curve_form" model="ir.ui.view">
        <field name="name">product.curve.form</field>
        <field name="model">product.template</field>
        <field name="inherit_id" ref="product.product_template_only_form_view"/>
        <field name="arch" type="xml">
            <div name="options" position="inside">
                <field name="product_website_sale_type" class="oe_inline"/><label for="product_website_sale_type" string="¿Se vende por curva?"/>
            </div>
            <field name="product_curve_id" position="replace"></field>
            <xpath expr="//notebook/page[@string='Variants']" position="after">
                <page string="Configurar Curva" attrs="{'invisible': [('product_website_sale_type','=', False)],'required': [('product_website_sale_type','=', True)]}">
                    <group>
                        <group>
                            <field name="product_curve_id" string="Tipo de Curva"/>
                        </group>
                        <group>
                            <field name="curva" string="Configuración de curva" attrs="{'invisible': [('product_website_sale_type','=', False)],'required': [('product_website_sale_type','=', True)]}"/>   
                        </group> 
                    </group>
                </page>
            </xpath>
        </field>
    </record>
  </data>
</openerp>