odoo/addons/account_voucher/account_voucher_workflow.xml

<?xml version="1.0" encoding="UTF-8"?>
<openerp>
	<data>

		<record id="wkf_voucher" model="workflow">
            <field name="name">account.voucher.basic</field>
            <field name="osv">account.voucher</field>
            <field name="on_create">True</field>
        </record>

        <record id="act_draft" model="workflow.activity">
            <field name="wkf_id" ref="wkf_voucher"/>
            <field name="flow_start">True</field>
            <field name="name">draft</field>
        </record>
        
        <record id="act_performa" model="workflow.activity">
            <field name="wkf_id" ref="wkf_voucher"/>
            <field name="name">performa</field>
            <field name="action">open_voucher()</field>
            <field name="kind">function</field>
        </record>
        
        <record id="act_posted" model="workflow.activity">
            <field name="wkf_id" ref="wkf_voucher"/>
            <field name="name">posted</field>
            <field name="action">proforma_voucher()</field>
            <field name="flow_stop">True</field>
            <field name="kind">function</field>
        </record>
        
        <record id="act_cancel" model="workflow.activity">
            <field name="wkf_id" ref="wkf_voucher"/>
            <field name="name">cancel</field>
            <field name="action">cancel_voucher()</field>
            <field name="kind">function</field>
        </record>
        
        <record id="t1" model="workflow.transition">
            <field name="act_from" ref="act_draft"/>
            <field name="act_to" ref="act_performa"/>
            <field name="signal">open_voucher</field>
        </record>
        
        <record id="t2" model="workflow.transition">
            <field name="act_from" ref="act_performa"/>
            <field name="act_to" ref="act_posted"/>
            <field name="signal">proforma_voucher</field>
        </record>
        
        <record id="t3" model="workflow.transition">
            <field name="act_from" ref="act_performa"/>
            <field name="act_to" ref="act_cancel"/>
            <field name="signal">cancel_voucher</field>
        </record>
        
        <record id="t5" model="workflow.transition">
            <field name="act_from" ref="act_draft"/>
            <field name="act_to" ref="act_cancel"/>
            <field name="signal">cancel_voucher</field>
        </record>
        
        <record id="t6" model="workflow.transition">
            <field name="act_from" ref="act_posted"/>
            <field name="act_to" ref="act_cancel"/>
            <field name="signal">cancel_voucher</field>
        </record>
	
		<record id="t7" model="workflow.transition">
            <field name="act_from" ref="act_cancel"/>
            <field name="act_to" ref="act_performa"/>
            <field name="signal">open_voucher</field>
        </record>
	</data>
</openerp>