python - How to add approval workflow OpenERP 7 -

here shows model class need add approval work flow.

class bpl_work_update(osv.osv):     _name = "bpl.work.update"     _description = "bpl work update"     _columns = {         'bpl_company_id':fields.many2one('res.company', 'company', help='company'),         'ref_no': fields.char('reference no', size=10,),         'offered_date': fields.date('offered date'),         # below lines related work update approve workflow (i refer hr.holidays model )         'state': fields.selection([('draft', 'to submit'), ('cancel', 'cancelled'), ('confirm', 'to approve'), ('refuse', 'refused'), ('validate1', 'second approval'), ('validate', 'approved')],             'status', readonly=true, track_visibility='onchange'),         'user_id': fields.many2one('hr.employee', 'add records', invisible=false, readonly=true),         'manager_id': fields.many2one('hr.employee', 'first approval', invisible=false, readonly=true),       }     _defaults = {                  'bpl_company_id':_default_company,                  'offered_date':fields.date.context_today,                  'state': 'draft',                  'user_id': lambda obj, cr, uid, context: uid,                  }  bpl_work_update() 

here shows view.xml file (i got lines here related work flow handling )

<header>     <button string="approve" name="validate" states="confirm"         type="workflow" groups="group_checkroll_user" class="oe_highlight" />     <button string="validate" name="second_validate" states="validate1"         type="workflow" groups="group_checkroll_manager" class="oe_highlight" />     <button string="refuse" name="refuse" states="confirm,validate,validate1"         type="workflow" groups="group_checkroll_manager" />     <button string="reset new" name="set_to_draft" states="cancel,refuse"         type="object" groups="group_checkroll_manager" />     <field name="state" widget="statusbar" statusbar_visible="draft,confirm,validate"         statusbar_colors='{"confirm":"blue","validate1":"blue","refuse":"red"}' /> </header> 

i have no idea how implement approval type work flow. refer hr.holidays model class unable got clear idea it. please me add level approve work order request. & please give me link refer regarding type of work flow creating..

now workflow buttons added form , shows correctly.but how handle those.? here screen

you can refer link : http://doc.openerp.com/v6.1/developer/07_workflows.html

you need create new workflow.xml file need define first workflow object creating, different activities want show in workflow , different transitions between activities. first refer above link, understand , after go developing it.

you did right thing assigning type="workflow" in button. here, name of button working signal in transition. means if flow signal, go checking in transition , transition, trigger function of activity which, transition created.