Description

E06 Queries on KB

17341015 Hongzheng Chen
Contents
1 Problem Description 2
2 Codes and Results 2
1 Problem Description
Given a KB Restaurants.pl, which describes the distribution of branches of 10 well-known restaurants in Guangzhou.
For example, restaurant(ajukejiacai,2007,yuecai) means that ajukejiacai was founded in 2007 and is a restaurant of yuecai. branch(ajukejiacai,xintiandi) means that ajukejiacai has a branch in xintiandi. district(xintiandi,panyu) means that xintiandi is an area of panyu district.
Please formulate each of the following questions as a query using Prolog’s notation, pose it to Prolog, and obtain Prolog’s answer:
1. What restaurants have branches in beigang?
2. What districts have restaurants of yuecai and xiangcai?
3. What restaurants have the least number of branches?
4. What areas have two or more restaurants?
5. Which restaurant has the longest history?
6. What restaurants have at least 10 branches?
Please define the new relation below using Prolog and test it.
• sameDistrict(Restaurant1, Restaurant2): Restaurant1 and Restaurant2 have one or more branches in the same district.
You should write down a listing that shows the queries you submitted to Prolog, and the answer returned. Hand in a file named E06 YourNumber.pdf, and send it to ai 201901@foxmail.com
2 Codes and Results
The below listing shows rules.pl file.
• numBranches/2: Calculate the number of branches of a specfic restaurant.
• sameDistrict/2: Check if two restaurants are in the same district.
numBranches(X,L) :- setof(Branch,Year^Type^(restaurant(X,Year,Type),branch(X,Branch)),Z), ,→ length(Z,L).
sameDistrict(X,Y) :- branch(X,Area1),branch(Y,Area2),district(Area1,Dist),district(Area2, ,→ Dist).
The below listing shows sol.pl program.
• Q1: Directly use branch(X,beigang).
• Q2: Similar to natural join in MySQL, but remember to use ^ to eliminate verbose output.
• Q3: Use the predefined numBranches/2 in rules.pl. If no restaurant has less branches than restaurant A, then restaurant A has the least number of branches. Here we use +setof to test if the return is an empty set.
• Q4: Use length to get number of restaurants in one area, and make the length is bigger or equal to 2.
• Q5: Similar to Q3 but change number of branches to founded year.
• Q6: Reuse the numBranches/2 function.
[’Restaurants.pl’,’rules.pl’].
%% Q1
findall(Rest,branch(Rest,beigang),Z).
%% Q2
setof(Dist,Loc^Rest1^Rest2^Year1^Year2^Loc1^Loc2^(restaurant(Rest1,Year1,yuecai), ,→ restaurant(Rest2,Year2,xiangcai),branch(Rest1,Loc1),branch(Rest2,Loc2),district( ,→ Loc1,Dist),district(Loc2,Dist)),Res).
%% Q3
findall(MinRest,(numBranches(MinRest,MinNum),+setof(SmallerRest,SmallerNum^(numBranches( ,→ SmallerRest,SmallerNum),MinNum > SmallerNum),Lst)),Z).
%% Q4
setof(Area,Lst^Len^(setof(Rest,branch(Rest,Area),Lst),length(Lst,Len),Len >= 2),Z).
%% Q5
findall(MinYearRest,(restaurant(MinYearRest,MinYear,T2),+setof(ShorterRest,T1^Year^( ,→ restaurant(ShorterRest,Year,T1),Year < MinYear),Lst)),Z).
%% Q6 setof(Rest,Num^(numBranches(Rest,Num),Num >= 10),Z).

I test the sameDistrict/2 rule for several cases shown below.