Last modified: 2019-03-13 12:33. Modified by Thomas Hallgren, Jonas Duregård and Aarne Ranta from earlier years' specifications by many other teachers at Chalmers and GU
The purpose of this assignment is to give you hands-on experience with designing, constructing and using a database for a real-world-like domain. You will see all aspects of database creation, from understanding the domain to using the final database from external applications.
To pass the programming assignment, you must pass all five tasks described on this page. You will do the assignment in groups of two. You need to form groups, register in Fire and request a PostgreSQL account in the first week of the course.
You must submit your solutions through the Fire reporting system, where you can also see deadlines for each task (link on main page).
You must submit your group's solutions to each task by the given deadline. After submission, your assignment will be graded ("pass" or "reject") and you will receive comments on your solution (for tasks 1, 2, and 3). If your submission is rejected, you are allowed to refine your solution and re-submit it.
To pass the final part of the assignment, you must demonstrate your system to one of the teachers. Your files for task 4 must be uploaded to the Fire system after you have demonstrated your system, and before the task 4 deadline.
In this assignment you will design and construct a database, together with a front end application, that handles university students and courses. You will do this in four distinct tasks:
All of the tasks are related to each other. They deal with the same database domain, and subsequent tasks build on earlier ones to varying degrees.
For each task you will hand in and get feedback on your results. Since errors in one task may propagate to the next one, it is wise to hand in your solutions early to get more chances for feedback. You can also ask assistants on lab sessions to have a quick look at your solution, if they are not to busy (not a guarantee that your submitted solution is accepted!).
Be sure to read through the full description of the assignment before you start since the requirements we place on the system must influence your initial design as well.
The domain that you will model in this assignment is that of courses and students at a university. So as not to make the task too large and unspecified, you will here get a description of the domain that restricts the problem somewhat. Note that the described domain is not identical to Chalmers or GU.
The university for which you are building this system is organized into departments for employees, such as the Dept. of Computing Science (CS), and study programmes for students, such as the Computer Science and Engineering programme (CSEP). Programmes are hosted by departments, but several departments may collaborate on a programme, which is the case with CSEP that is co-hosted by the CS department and the Department of Computer Engineering (CE). Department names and abbreviations are unique, as are programme names but not necessarily abbreviations.
Each study programme is further divided into branches, for example CSEP has branches Computer Languages, Algorithms, Software Engineering etc. Note that branch names are unique within a given programme, but not necessarily across several programmes. For instance, both CSEP and a programme in Automation Technology could have a branch called Interaction Design. For each study programme, there are mandatory courses. For each branch, there are additional mandatory courses that the students taking that branch must read. Branches also name a set of recommended courses from which all students taking that branch must read a certain amount to fulfill the requirements of graduation, see below.
A student always belongs to a programme. Students must choose a single branch within that programme, and fulfill its graduation requirements, in order to graduate. Typically students choose which branch to take in their fourth year, which means that students who are in the early parts of their studies may not yet belong to any branch.
Courses are given by a department (e.g. CS gives the Databases course). Each course has a unique six character course code. All courses may be read by students from any study programme. Some courses may be mandatory for certain programmes, but not so for others. Students get credits for passing courses, the exact number may vary between courses (but all students get the same number of credits for the same course). Some, but not all, courses have a restriction on the number of students that may take the course at the same time. Courses can be classified as being mathematical courses, research courses or seminar courses. Not all courses need to be classified, and some courses may have more than one classification. The university will occasionally introduce new classifications. Some courses have prerequisites, i.e. other courses that must be read before a student is allowed to register to it.
Students need to register for courses in order to read them. To be allowed to register, the student must first fulfill all prerequisites for the course. It should not be possible for a student to register to a course unless the prerequisite courses are already passed. It should not be possible for a student to register for a course which they have already passed.
If a course becomes full, subsequent registering students are put on a waiting list. If one of the previously registered students decides to drop out, such that there is an open slot on the course, that slot is given to the student who has waited the longest. When the course is finished, all students are graded on a scale of 'U', '3', '4', '5'. Getting a 'U' means the student has not passed the course, while the other grades denote various degrees of success.
A study administrator can override both course prerequisite requirements and size restrictions and add a student directly as registered to a course. (Note: you will not implement any front end application for study administrators, only for students. The database must still be able to handle this situation.)
For a student to graduate there are a number of requirements they must first fulfill. They must have passed (have at least grade 3) in all mandatory courses of the study programme they belongs to, as well as the mandatory courses of the particular branch that they must have chosen. Also they must have passed at least 10 credits worth of courses among the recommended courses for the branch. Furthermore they need to have read and passed (at least) 20 credits worth of courses classified as mathematical courses, 10 credits worth of courses classified as research courses, and one seminar course. Mandatory and recommended courses that are also classified in some way are counted just like any other course, so if one of the mandatory courses of a programme is also a seminar course, students of that programme will not be required to read any more seminar courses.
You will design and implement a database for the above domain, and a front end application intended for students of the university. Through the application they should be able to see their own information, register to, and unregister from courses.
Formally, your application should have the following modes:
Your task is to construct a first version the database by implementing the database schema in a database engine (PostgreSQL). The schema for this part is given in this file: Abstract schema for database task 1
Note that the schema is somewhat incomplete, but that will be fixed in part two of the assignmnent.
You should implement the schema with CREATE TABLE statements that
Thus you should create all tables, marking key and foreign key constraints in the process, and you should also insert basic checks that ensure that only valid data can be inserted in the database. Examples of invalid data would be the grade '6', or a course that takes a negative number of students.
When you have created the tables, you should fill the tables with example data. Ordinarily, this is a time-consuming but important part of the development of a database. Having data in the database is crucial in order to properly verify that it behaves the way that you expect it to. The tables should be filled with enough data so that it is possible to test that your application can handle the various operations specified above. Just inserting tons of data is of no use if the data still doesn't test all parts of the database.
In this course however, we have decided to just give you a set of insert that should work (possibly with slight adjustments): inserts.sql. Note the various corner cases covered by the tests:
Following the system specification, create these views:
BasicInformation(idnr, name, login, program, branch)
For all students, their national identification number, name, login, their program and the branch (if any).
The branch column is the only column in any of the views that is allowed to contain NULL.
FinishedCourses(student, course, grade, credits)
For all students, all finished courses, along with their codes, grades
(grade 'U', '3', '4' or '5') and number of
credits. The type of the grade should be a character type,
e.g. CHAR(1).
PassedCourses(student, course, credits)
For all students, all passed courses, i.e. courses finished with a grade
other than 'U', and the number of credits for those courses. This view
is intended as a helper view towards later views (and
for task 4), and will not be directly used by your application.
Registrations(student, course, status)
All registered and waiting students for all courses, along with their
waiting status ('registered' or 'waiting').
UnreadMandatory(student, course)
For all students, the mandatory courses (branch and programme) they have
not yet passed. This view is intended as a helper view towards the
PathToGraduation view, and will not be directly used by your
application.
PathToGraduation(student, totalCredits, mandatoryLeft, mathCredits, researchCredits, seminarCourses, qualified)
For all students, their path to graduation, i.e. a view with columns for
student: the student's national identification number.
totalCredits: the number of credits they have taken.
mandatoryLeft: the number of courses that are mandatory for a branch or a program they have yet to read.
mathCredits: the number of credits they have taken in courses that are classified as math courses.
researchCredits: the number of credits they have taken in courses that are classified as research courses.
seminarsCourses: the number of seminar courses they have read.
qualified: whether or not they qualify for graduation. The SQL type of this field should be
BOOLEAN (i.e. TRUE or FALSE).
Hint1: Make a query for the data of each column and when they all work, put them in a WITH clause and use a chain of (left) outer joins to combine them.
Hint2: Use COALESCE to replace null values with 0 (e.g. COALESCE(totalCredits,0) AS totalCredits. Also, keep in mind that comparing null values with anything gives UNKNOWN!
Hint3: A query containing student/classification/credit with a row for each classification of each course every student has passed may be useful.
Make sure that your views use the right names of columns! Use AS to name a column.
Testing The file runtests.sql automatically runs the files for this assignment. The file output.txt contains the expected output of doing this. Run the file (with \i runtests.sql in psql) and make sure your output matches the example (assuming you use the provided insert.sql file) and that you get no errors (order of rows may possibly vary). This is not a perfect guarantee that your code works as it should, but it does find several common errors.
Deliverables: For task 1, you should submit the following files through Fire:
tables.sql: your SQL code for creating the tables.
insert.sql: OPTIONAL, your SQL code containing the insert statements for the data IF IT DIFFERS FROM THE FILE YOU WERE GIVEN. Also include a short comment next to every change you made to the file.
views.sql: your SQL code for creating the listed views.
explanation.txt OPTIONAL, this file is only required if you did not get all the tests provided to work exactly as intended, and should contain a short description of the problem. Submissions that do not contain this file and fail to pass the tests will be summarily rejected without comments.
Note that SQL code should be in plain text format. Make sure that PostgreSQL can execute your files on an empty database before you hand them in. Do not have the "delete everything"-statement in any of the files you submit.
The task in this lab is to take a look back at the database implemented in Lab 1 and check how we should have done it. More precisely, we will
There are many interesting outcomes that may result from this study:
First create an E-R diagram that correctly models the domain described in the Domain description above.
You can use any tool you like
for this task, as long as you hand in your solution as an image in one of
the formats .png, .jpg, .gif or .pdf and as a schema in a pure text file
(in a format similar to task1.txt).
We recommend you use Dia.
You must in both cases use the translations specified in the lectures, and mark the keys and references properly.
Hint: if your diagram does not contain at least one weak entity, at least one ISA relationship, and at least one many-to-at-most-one relationship, you have probably done something wrong.
Your second task is to formulate all functional dependencies in the domain and derive a valid schema from them. This should be done mostly independently of the E-R design and of the schema in task1.txt.
Domain(....). You may look in the schema from your ER model for this.
Domain(....).
Do not just extract them from your ER-model!
Here is a non-exhaustive list of things you may want to consider when
searching for functional dependencies:
Domain(....), as well as all BCNF violations.
Domain(....) to distinct tables by using the BCNF normalization algorithm.
Hint: the Query Converter (link on main page) can automate much of the analysis, as soon as you have identified the functional dependencies yourself. It can get slow when the schema is very large, but you can then just reload the page to kill the process.
Hint: The final schema should contain at least four additional relations compared to the schema in Task 1, and at least 3 UNIQUE constraints (one is only required for technical reasons to enable a constraint that prevents students from chosing a branch in the wrong program).
Deliverables: For Task 2, you should submit the following files through Fire
ER.png: your E-R diagram as a .png, .jpg, .gif or .pdf file
ER-schema.txt: the database schema derived from your E-R diagram, as a text file (no PDF, no Microsoft Word, no HTML!)
FD.txt: your Domain(...) schema together with the functional dependencies you have found
(you can omit dependencies that can be derived from the ones you mention)
FD-schema.txt: the decomposed schemas using the BCNF algorithm
final-schema.txt: your final database schema
tables.sql, views.sql, inserts.sql: Your modified database code.
Criteria of acceptance:
ER.png: the E-R diagram must be syntactically correct and a reasonable model for the domain (and you cannot do this without weak entities and ISA entities!)
ER-schema.txt: the ER-schema must be correctly derived from the diagram
FD.txt: you should have found all and only the reasonable functional dependencies in the domain (derived ones can be omitted)
FD-schema.txt: the decompositions should be correct
(this is partly automatic if you use Query Converter, but you should make sure to mark the keys and references)
final-schema.txt: Your final schema that models the domain as closely as possible (some things will simply not be possible to do in schemas, like checking that there are no circular requirements for courses or that a student can not register for a course they have already passed).
*.sql: The current executable code for your database, including all the changes made from this design task. Should contain no DROPS or other debug-code, just the code for creating the tables, views, and test data - all expanded/modified to work with the new design.
When your tables and views are implemented in Task 2, the next task is to create two triggers to handle some key issues in registration and unregistration. Here is a piece of code to get you started on the first trigger:
But first, you should define one more view that can be used by your triggers, and your application in Task 4:
CourseQueuePositions(course,student,place):
For all students who are in the queue for a course, the course code, the
student's identification number, and the student's current place in the
queue (the student who is first in a queue will have place "1" in that
queue, etc.). This view is trivial if you store the positions directly in the database, but not if you store e.g. registration timestamps.
When a student tries to register for a course, it is possible that the course is already full, in which case the student should be put in the waiting list for that course. When a student unregisters, it might be that there is now room for some student who is in the waiting list, and who should then be registered for the course instead. Such things are typically handled via triggers. You should write two triggers:
You need to write the triggers on the view Registrations instead of on the
tables themselves (the view was built in task 1 above). (One reason for this is
that we "pretend" that you only have the privileges listed under Task 4, which
means you cannot insert data into, or delete data from, the underlying tables
directly. But even if we lift this restriction, there is another reason for not
defining these triggers on the underlying tables - can you figure out why?)
Hint1: Write your triggers incrementally, first make a registration trigger that just always give an error and test that it works, then make it give an error only if the student is already registered (or waiting) and otherwise register it, then make it give a different error if the student is missing prerequisites, then make it put the student in a waiting list if the course is full, and so on.
Hint2: One way to check if a course is full: Count the number of courses with that code and more students than its seat capacity. The count will be 1 or 0 (0 meaning either it has no limit or the limit is not exceeded).
Testing Make a file tests.sql with inserts and deletes that test all cases of your triggers. Write a short comment (line starting with --) over each insert/delete that states what is tested the expected outcome (change/error).
Hint1: Your tests need to test every way a registration could fail, and the outcomes of successfull registrations/unregistrations. The latter includes:
Hint2: Look at the list at the end of Task 4 for some ideas on what to test.
Deliverables. For task 3, you should hand in the following files:
setup.sql: SQL code that sets up your database for testing the
triggers. This will normally be the concatenation of files
tables.sql, insert.sql and views.sql from Task 2.
We must
be able to test your triggers by executing the files setup.sql
and triggers.sql, in that order.
triggers.sql: SQL code for creating the two triggers and the CourseQueuePositions view.
tests.sql The testing code for your triggers.
Make sure that PostgreSQL can execute your files before you hand them in.
The last part of this assignment is to write an application that students can use to communicate with your database. This application should connect to the PostgreSQL database to request and insert the proper data, and can be either
To your help when writing your application we provide you with a stub file that contains the code for connecting to PostgreSQL on the local system. It also contains hooks for the three operating modes of the application, and this is where you should insert your code. The idea is that you should not need to focus so much on the pure Java parts of the application, but rather get straight down to business with the database-interfacing code.
The stub file is here: StudentPortal.java.
The intended behavior of the program is that you use it from the command line, giving some student identification number as an argument (what exactly that is depends on your design). This corresponds to the student "logging on" to the portal. Once logged on, the student can choose one of the three modes "Information", "Register" or "Unregister". If the first is chosen, all information for that student should be printed. Exactly what information must be printed is given by the system requirements specified above. If one of the latter modes are chosen, the student will be prompted for a course to register to or unregister from, and the application should perform the requested operation and print the result (success, failure).
The stub file can be compiled and run as it is, only nothing will happen in any of the modes. Your task is thus to fill in the actual logic of these three tasks.
Running your application could look like this:
$> java StudentPortal 1234567890
Welcome!
Please choose a mode of operation:
? > i
Information for student 1234567890
-------------------------------------
Name: Emilia Emilsson
Student ID: emem
Line: Information Technology (IT)
Branch: Systems Development
Read courses (name (code), credits: grade):
Set Theory (MAT050), 5p: 5
Functional Programming (TDA450), 10p: 5
Object-Oriented Systems Development (TDA590), 10p: 4
Registered courses (name (code): status):
Databases (TDA356): registered
Algorithms (TIN090): waiting as nr 3
Seminar courses taken: 0
Math credits taken: 5
Research credits taken: 0
Total credits taken: 25
Fulfills the requirements for graduation: no
-------------------------------------
Please choose a mode of operation:
? > r TDA350
You are now successfully registered to course TDA350 Cryptograhy!
Please choose a mode of operation:
? > r TDA381
Course TDA381 Concurrent Programming is full, you are put in the
waiting list.
Please choose a mode of operaion:
? > quit
Goodbye!
$>
Note that the exact formatting is only a suggestion: you may choose to format your output differently as long as you give the proper information back to the user.
To get access to the PostgreSQL jdbc drivers from your application, you should download it from https://jdbc.postgresql.org and import it into your java CLASSPATH.
Alternatively you can import the file into an Eclipse project if you are using Eclipse.
If you are impementing your Student Portal in Java you can skip the next section about Haskell and continue with Requirements and deliverables below.
We provide the Haskell modules described below as a starting point for your
work. You can download them all at once from
task4haskell.zip.
StudentPortal.hsWe also provide the following modules, which you can use unchanged:
StudentPortalCommon.hsSqlRows.hsStudentPortalCommon. Using this module is
optional, but it can simplify the code somewhat.
StudentPortalCLI.hsStudentPortal.java.
StudentPortal3p.hscabal install threepenny-gui.
The two user interfaces modules both export a function called
studentPortal, which is called from the main function, so
you switch between the two user interfaces simply by changing which user
interface module you import.
No other changes in the code should be needed.
An introduction to HDBC can be found in the book Real World Haskell, Chapter 21. Using Databases. Here we just give a brief summary of what you need to know.
As you can see in the main module StudentPortal.hs, to access your PostgreSQL database from Haskell using HDBC, you need to import two modules that come from two packages:
Database.HDBC
that comes from the package
HDBC and contains functions
that work with several different SQL databases. You probably only need
to use a few functions from this module:
run,
quickQuery',
withTransaction,
fromSql,
toSql,
handleSqlError.
Database.HDBC.PostgreSQL
that comes from the package
HDBC-postgresql
and contains functions to connect to a PostgreSQL database.
You probably only need to use one function form this module:
connectPostgreSQL.
You can install both packages at once e.g. by running
cabal install HDBC-postgresql.
With HDBC, all the values that you retrieve from or send to the database have
the Haskell type SqlValue. For example, the function
quickQuery' that sends an SQL query to the database and retrieves
the result has type:
quickQuery' :: Connection -> String -> [SqlValue] -> IO [[SqlValue]]
HDBC provides the overloaded functions toSql and fromSql that convert
between SqlValue and normal Haskell types, like String and Int.
You can also convert from SqlValue to e.g. Maybe String, if you
are retrieving a string that might be NULL.
The module SqlRows mentioned above provides functions to convert
whole rows of SQL values at once, which allows you to write functions like
the following:
getContinent :: Connection -> String -> IO [(String,Int)]
getContinent conn continent =
fromRowsM =<< quickQuery' query [toSql continent]
where
query = "SELECT name,population FROM Countries WHERE continent=?"
Here, the rows returned by quickQuery' are converted from
[[SqlValue]] to the type [(String,Int)]. For correctly constructed
queries the conversion should succeed, but in general it might fail,
e.g. if the rows in the query result don't contain the expected number of
values (two in this example) or if the individual values in the rows
can not be converted to the expected Haskell types
(String and Int in this example).
The function fromRowsM and fromRowM are monadic
and raise an error in the IO monad if the conversion fails. Errors in the
IO monad can be caught using functions from the library
module System.IO.Error. There are also pure variants fromRows
and fromRow that call error when conversion fails.
fromRowM :: (FromRow a,Monad m) => Row -> m a
fromRowsM :: (FromRow a,Monad m) => Rows -> m [a]
fromRow :: FromRow a => Row -> a
fromRows :: FromRow a => Rows -> [a]
Your Student Portal application should behave as if it has only the following privileges:
SELECT ON Course
SELECT ON Student
SELECT ON BasicInformation
SELECT ON FinishedCourses
SELECT ON Registrations
SELECT ON CourseQueuePositions
SELECT ON PathToGraduation
INSERT ON Registrations
DELETE ON Registrations
We will check your submitted code to ensure that you adhere to these privileges, even though we cannot get the system to enforce them automatically.
Deliverables:
StudentPortal.java or StudentPortal.hs with your additions, submitted via Fire AFTER DEMONSTRATING (do not submit anything before you have been accepted).
You must come to one of the supervision sessions and demonstrate your running application, and we will accept or reject it on the spot (pending the check of the submitted code for authority violations). You should write the name of the teacher you demonstrated to along with the time when you were accepted in a comment when you submit.
Demonstration should take around 10 minutes per group. Test running through the list below at least once before you demonstrate. Also have an interface for running queries on your database open to show the contents of CourseQueuePositions and Registrations.
As you probably realize, if all of you wait until the last session, we will quite simply not have time for everyone, so come as early as possible!
Here is a list of what we will test your application for (be prepared to run these when demonstrating):
You must demo your working project before or on the last lab session.