cps721: Assignment 1 (100 points).
Due date: Electronic file – before Monday, September 27, 2021, 17:00.
You have to work in groups of TWO, or THREE. You cannot work alone.
YOU SHOULD NOT USE “;” (disjunction) “!” (cut) AND “−>” IN YOUR PROLOG PROGRAMS.
You can discuss this assignment only with your CPS721 group partners or with the CPS721 instructor. By sub-
mitting this assignment you acknowledge that you read and understood the course Policy on Collaboration in
homework assignments stated in the CPS721 course management form.
This assignment has 3 pages. On the 3rd page, you can find the rules about submitting this assignment electronically. Im-
properly submitted assignments will not be assessed. Late assignments are not allowed: see the CMF.
1 (40 points). This problem is designed to get you started in Prolog. Make up a simple knowledge base (KB) of atomic
sentences (10-15 atomic sentences for each predicate) about movies (not necessarily real ones), so that most of the queries below
will successfully retrieve answers from your KB. If you would like to read about real movies, you can consult http://www.imdb.com/
Keep your KB in the file movies.pl Use the following predicates.
actsIn(Person,Movie) – the Person is acted in the Movie.
directs(Person,Movie) – the Person directed the Movie.
released(Movie,Year) – the Movie was released during the Year.
Now pose the following queries to Prolog, and obtain Prolog’s answers. You are not allowed to write any rules in this part
of your assignment. You can only write atomic statements to implement your KB, and Prolog queries to retrieve answers from
your KB. As for syntax of your queries, you can use only negation “not”, conjunction, and predicates mentioned above with
variables or constants as arguments. You cannot use any other predicates.
1. Did Robert De Niro star in Awakenings?
2. Who directed Rain Man?
3. Did anyone star in both Apocalypse Now and The Godfather?
4. Was there a movie released in 2020 where neither Al Pacino nor Leonardo DiCaprio acted?
5. Does any movie have more than one director? Have Prolog list all such movies and their directors by using the ; command
(if you work with the command-line Prolog) or by using more button (if you work with a GUI version of ECLiPSe Prolog).
6. Did any director of “Forrest Gump” ever directed movies released during or after 2000? Note that X < Y (and X > Y )
is Prolog’s less than (greater than, respectively) predicate: X < Y succeeds if the number X is less than the
number Y . Similarly, X =< Y succeeds if the number X is less than or equal to the number Y . Both variables X,Y
should be instantiated before comparison X =< Y .
7. Has anyone acted in more than two movies released in the same year?
8. Who has worked with the same director in different years? Have Prolog list all such actors, directors, the movies they
worked on together, and the years they were released using the ; command (or by clicking the “more” button on GUI).
9. Has anyone directed only one movie in 2021? Suppose the answer Yes. Add new atomic statements about this director
and imaginary movie s/he directed in 2021. After this change, if answer to your query is still yes, then the query is wrong.
Pay attention to the phrase only one and think how it can be implemented for an arbitrary large KB.
10. What movie has the earliest year of release? Note that if you add to your KB a new (real or imaginary) movie with
an earlier release date (e.g., a movie directed by Charlie Chaplin that was not previously in your KB), but submit same
query, then answer to your query should change too, if the query is correct.
Handing in solutions: (a) An electronic copy of your program with all atomic statements (the name of this file must be
movies.pl); (b) An electronic copy of your session with Prolog that shows clearly the queries you submitted to Prolog, and the
answers that were returned (the name of this file must be movies.txt).
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2 (20 points). This problem will exercise what you have learned about rules in Prolog, by having you implement a set of
rules for calculating the final letter grade in the CPS721 course.
a) Write a Prolog file grade.pl with the knowledge base (KB) about quizzes, assignments and tests in CPS721. Your KB
should include a collection of atomic statements in Prolog using the following predicates:
assignment(Number,AScore) – a student got AScore for the assignment Number, where 0 ≤ AScore ≤ 100.
quiz(Number,QScore) – a person has received QScore for the quiz Number, where 0 ≤ QScore ≤ 2.
midterm(Mark1) – a student has received Mark1 for the midterm test, where 0 ≤ Mark1 ≤ 20%.
exam(Mark2) – a person received Mark2 for the final exam, where 0 ≤ Mark2 ≤ 50%.
b) Subsequently, use these predicates to define new predicates as specified below. Write the rules in the same file grade.pl
• Write the rule calculating the total value A of the five assignments. Use the new predicate sumAssignments(A) in the
head of your rule and relate it with the atomic statements about the scores for all five assignments. Since in CPS721 each
assignment is out of 100 points, but in total the assignments contribute 10% of the final grade, you have to scale down
the sum of scores of all assignments to calculate the number 0 ≤ A ≤ 10%.
• Introduce new predicate sumQuizzes(Q) and use it to calculate the total value 0 ≤ Q ≤ 20% contributed to the final grade
by all the ten lab quizzes. Notice each lab quiz is marked out of 2 points.
• Let predicate grade(G) is true if G is the final grade in % obtained by a student in the CPS721 course. Write a single
rule defining this predicate using the predicates introduced before: sumAssignments(A), sumQuizzes(Q), midterm(M),
exam(E). The CPS721 grading scheme is defined in the CPS721 course management form.
• Let predicate letter(L,G) holds if L is the University letter grade representing the total numerical course grade 0 ≤ G ≤
100%. Consult the Ryerson university Web site for an exact definition of the final letter grades in the Faculty of Sciences.
Write several Prolog rules implementing this predicate letter(L,G) according to the Faculty of Science university grading
scheme. Make sure you do rounding correctly when calculating the letter grade.
(c) Once you have implemented all these predicates, test your rules by submitting queries to Prolog, obtain answers, and
store a copy of your interaction with Prolog in a file. Try at least 5 queries to demonstrate your program works correctly. It
is up to you to decide which queries you would like to try. In this and in the next question, when you write rules (conditional
clauses), you are not allowed to use the following commands: “;” (disjunction),
Handing in solutions. An electronic copy of: (a) your program (the name of the file must be grade.pl) that includes all
your Prolog rules and your atomic statements; (b) your session with Prolog, showing the queries you submitted and the answers
returned (the name of the file must be grade.txt). It is up to you to formulate a range of queries that demonstrates that your
program is working properly.
3 (40 points). As you may know, Geographic Information Systems (GIS) technology is based on cartography, databases
and statistical analysis. The world’s first fully-operational GIS was developed in 1962 in Ottawa, Ontario, Canada by the federal
Department of Forestry and Rural Development. For the purposes of this assignment, imagine a prototype of a GIS that can
answer queries about a city through a hand-held mobile device. This imaginary system would have information about all streets,
subway stations, buildings and other locations in the city. Below, we speak of “entities” to use a generic term that may represent
city streets, subway stations, universities, libraries or any other locations of importance. For the GIS to operate correctly, it
should be provided with numerous logical rules for reasoning about directions and entities in the city. In this question, you
are asked to implement recursive rules about the four geographic cardinal directions only. More specifically, you are given the
following predicates (east includes proper east, south-east and north-east directions):
eastOf(Entity1,Entity2) – Entity1 is east of Entity2, westOf(Entity1,Entity2) – Entity1 is west of Entity2
southOf(Entity1,Entity2) – Entity1 is south of Entity2, northOf(Entity1,Entity2) – Entity1 is north of Entity2.
(a) Start with implementing a small knowledge base (KB) of atomic statements. Your KB can be real, e.g., it include
information about streets in Toronto, or it can be imaginary; this is up to you. Your atomic statements can use 4 new predicates
describing relations between the regions that are immediately adjacent to each other in one of the 4 cardinal directions.
(b) Next, add logical rules (conditional statements). Given the predicates mentioned above and your new predicates from
(a), write all recursive rules one might need to reason about cardinal direction of any entity with respect to others. Do not
introduce any other predicates. Remember that you have to write all correct rules, and nothing but correct rules. For example,
if we know that X is east of Y , we should be able to conclude that Y is west of X . In addition, if we know that X is south of
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Y , and Z is east of Y , then we know that X is south of Z, and so on. Warning: as stated on the top of this assignment, when
you write rules in Prolog, you are not allowed to use the following commands: “;” (disjunction), “!” (cut) and “−>” (if-then).
(c) Test your rules on your atomic statements using queries about entities named in your KB. Try as many testing queries
as needed to make sure that you got a complete set of correct rules. In particular, make sure you get all correct and only correct
answers when you submit a query ?− westOf(X,Y ). and similar queries with variables. Repetitions of correct answers are
allowed. The queries up to you; they should convince the TA that you have implemented a correctly working recursive program.
Handing in solutions. An electronic copy of: (a) your program (the name of the file must be gis.pl) that includes all your
correct rules. (b) An electronic copy of your session with Prolog that shows clearly the queries you submitted to Prolog, and
the answers that were returned (the name of this file must be gis.txt); (c) Hand in a printout of gis.pl and gis.txt) in class.
How to submit this assignment. Read regularly Frequently Answered Questions and replies to them that are linked from the
Assignments Web page at
http://www.scs.ryerson.ca/˜mes/courses/cps721/assignments.html
If you write your code on a Windows machine, make sure you save your files as plain text that one can easily read on Linux
machines. Before you submit your Prolog code electronically make sure that your files do not contain any extra binary symbols:
it should be possible to load grade.pl or gis.pl into a recent release 6 of ECLiPSe Prolog, compile your program and
ask testing queries. TA will mark your assignment using ECLiPSe Prolog. If you run any other version of Prolog on your
home computer, it is your responsibility to make sure that your program will run on ECLiPSe Prolog (release 6 or any more
recent release), as required. For example, you can run a command-line version of eclipse on moon remotely from your home
computer to test your program (read handout about running ECLiPSe Prolog). To submit files electronically do the following.
First, create a zip archive:
zip yourLoginName.zip movies.pl movies.txt grade.pl grade.txt gis.pl gis.txt
where yourLoginName is the Ryerson login name of the person who submits this assignment from a group. Only one student
is allowed to sibmit an assignment from a group. Remember to mention at the beginning of each file student, section numbers
and names of all people who participated in discussions (see the Course Management Form). You may be penalized for not
doing so. Second, upload your ZIP file yourLoginName.zip
to D2L into “Assignment 1” folder. Make sure it includes all your files. Improperly submitted assignments will not be marked.
In particular, you are not allowed to submit your assignment by email to a TA or to the instructor.
Revisions: If you would like to upload a revised copy of your assignment, then simply upload it again. (The same person
must upload.) A new copy of your assignment will override the old copy. You can upload new versions as many times as you
like and you do not need to inform anyone about this. Do not ask your team members to upload your assignment, because TA
will be confused which version to mark: only one person from a group should submit different revisions of the assignment.
The groups that submit more than one copy of their solutions will be penalized. The time stamp of the last file you upload will
determine whether you have submitted your work on time.
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