Prolog project getting started

Question

This is my first time asking a question on here. Sorry if I do something incorrectly.

First, I want to be up front; this is a homework question. I am not looking for anyone to do it for me. I just need help getting started.

The problem is- Table of data Using above information, Write a prolog program to answer the following queries. Please note that you cannot simply answer these queries with only facts, you should answer then using facts and rules.

A. Which country/countries has/have the largest case number?

B. Which country/countries has/have the smallest number of deaths?

C. Which country has the largest case number or the largest number of deaths?

D. Which country has the largest case number less than 5?

E. How many cases are reported for Austria?

F. How many cases are reported for the Asia?

G. How many cases are reported for the Asia and middle east?

H. Which region has the smallest case number?

I. Which region has the largest number of deaths?

J. Which regions have a smaller case number than Europe?

K. Which country/countries has/have a larger number of deaths than Iran?

L. Which country/countries has/have a larger case number and a larger number of deaths than Iran?

M. Which country/countries has/have a larger case number or a larger number of deaths than Iran?

N. What is the average case number in this report?

Ok so. I roughly understand how to complete the rules for how many cases are reported in X. That seems easy. But what I don't understand, is how we can traverse data and compare it in Prolog. In java for example, I would just put all the values in an array and sort it. Making this easy.

My question boils down to this:

1. How would you store the initial data from the table? (facts)
2. how would you write the rules to find the largest element?

Answer 1

Example for question A, using swi-prolog:

country_cases_deaths('Jordan', 35, 14).
country_cases_deaths('UK', 5, 3).
country_cases_deaths('Someplace Else', 35, 5).
country_cases_deaths('Austria', 2, 1).

country_max_cases(Country, MaxCases) :-
    aggregate_all(
        % Want the maximum
        max(Cases),
        % This is the filter
        country_cases_deaths(_, Cases, _),
        % Variable to put the max in
        MaxCases
    ),
    % Lookup country - could be multiple countries having the same max
    country_cases_deaths(Country, MaxCases, _).

Result:

?- country_max_cases(Country, MaxCases).
Country = 'Jordan',
MaxCases = 35 ;
Country = 'Someplace Else',
MaxCases = 35.

?- findall(Country, country_max_cases(Country, _), Countries).
Countries = ['Jordan','Someplace Else'].

Some useful links: aggregate_all (click the orange "show source" icon in the top right, to see sourcecode), discussion