To create an osv_memory wizard systems in openerp-7 and openerp-8(Odoo), follow the below steps.

In the action that opens the object, you can put </br>
     <field name="target"/> 
    It means the object will open in a new window.
    On a button,you can use <button special=cancel/> to close the window.

class config_compute_remaining(osv.osv_memory): 
_name=config.compute.remaining 
def _get_remaining(self,cr, uid, ctx): 
if active_id in ctx: 
return self.pool.get(project.task).browse(cr,uid,ctx[active_id]).remaining_hours 
return False 
_columns = { 
remaining_hours : fields.float(Remaining Hours, digits=(16,2),), 
} 
_defaults = { 
remaining_hours: _get_remaining 
} 
def compute_hours(self, cr, uid, ids, context=None): 
if active_id in context: 
remaining_hrs=self.browse(cr,uid,ids)[0].remaining_hours 
self.pool.get(project.task).write(cr,uid,context[active_id], 
{remaining_hours : remaining_hrs}) 
return { 
type: ir.actions.act_window_close, 
} 
config_compute_remaining() 

View is same as normal view (Note buttons)

<record id="view_config_compute_remaining" model="ir.ui.view"> 
<field name="name">Compute Remaining Hours </field> 
<field name="model">config.compute.remaining</field> 
<field name="type">form</field> 
<field name="arch" type="xml"> 
<form string="Remaining Hours"> 
<separator colspan="4" string="Change Remaining Hours"/> 
<newline/> 
<field name="remaining_hours" widget="float_time"/> 
<group col="4" colspan="4"> 
<button icon="gtk-cancel" special="cancel" string="Cancel"/> 
<button icon="gtk-ok" name="compute_hours" string="Update" type="object"/> 
</group> 
</form> 
</field> 
</record> 

Note: Here in osv_memory wizard I have created a normal object, But instead of inheriting wizrad from osv.osv, I have Inherit it from osv.osv_memory.
Methods of wizard are in object and if the wizard is complex, You can define workflow on object as I did.