farm/security/farm_security.xml

<?xml version="1.0" encoding="UTF-8"?>
<openerp>
<data noupdate="0">
    <record model="ir.module.category" id="module_category_farm">
            <field name="name">Farm</field>
            <field name="description">Helps you manage your farms</field>
            <field name="sequence">4</field>
    </record>
    <record id="group_farm_user" model="res.groups">
        <field name="name">FarmUser</field>
        <field name="category_id" ref="module_category_farm"/>
    </record>
    <record id="group_farm_manager" model="res.groups">
        <field name="name">FarmManager</field>
        <field name="category_id" ref="module_category_farm"/>
    </record>
</data>
</openerp>