i need a train to cambridge , please london liverpool street .
i would love to help you with that ! where is your departure location ?
{'service': 'train', 'act': 'request', 'slot_name': 'day', 'value': '?'} {'service': 'train', 'act': 'request', 'slot_name': 'leave', 'value': '?'}
what day are you leaving and what time to you want to depart ?