inform((_:search,type,'Taxi'))
user
I need to book a taxi plese
request((_:search,arrive_by,?);(_:search,destination,?);(_:search,type,'Taxi'))
system
What time will you be arriving to your destination please .
inform((_:search,arrive_by,'12:45');(_:search,type,'Taxi'))
user
I want to arrive by 12:45 .
request((_:search,departure,?);(_:search,type,'Taxi'))
system
What is your departure site ?
inform((_:search,departure,'cambridge and county folk museum');(_:search,type,'Taxi'))
user
I 'm leaving from cambridge and county folk museum .
request((_:search,destination,?);(_:search,type,'Taxi'))
system
What is your destination ?
inform((_:search,destination,'trinity college');(_:search,type,'Taxi'))
user
I 'm going to trinity college .
system
Booking completed ! 
 Booked car type white skoda 
 Contact number 07852790062
_:search type Taxi
_:search destination ?
_:search arrive_by 12:45
_:search type Taxi
_:search destination ?
_:search arrive_by 12:45
_:search departure cambridge and county folk museum
_:search type Taxi
_:search arrive_by 12:45
_:search departure cambridge and county folk museum
_:search destination trinity college
_:search type Taxi