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I am new to using UML and I am not sure if my diagram is correct. I would like some advice from someone more experienced than me.
The statement of my problema says:
Students study courses and each student can take several courses "studies" each. Any course can have more than one student studying it.
Students, who are identified by a numerical code, have a name, date of birth and one or more nationalities.
A student who studies can receive scholarships.
A Student can recieve more than one scholarship per course. And an
individual scholarship can be given to more than one student. The
scholarships have a numeric code, which identifies them, a name, a
base amount and different conditions to be fulfilled at the time of
the assignment.
My proposal is the following:
What I want is to represent students, grants and the courses the student takes, and I am not sure if I should use an associative relation or a ternary relation.
Can anybody confirm if my proposal UML diagram is the right one?
The only statement directly relating students, courses & grants is the unclear "[a s]tudent can receive more than one grant per course".
It only actually says that each student-course pair can have more than one associated grant. (Maybe the author of the assignment thought that that "per" sentence is saying more than that, but it's not.) It doesn't say of a student whether their grants depend on their courses, and if so how. Your design is best when given a triplet you can't tell anything about any other triplet. The design with Takes(student,course) & Receives(student, course, grant) with th FK (foreign key) {student, course} from Receives to Takes is best when if you know a student & course pair then you know its grants. If grants are given to a student independently of courses then a design with Takes(student,course) & Receives(student,grant) is enough.
Clarify with your instructor.
Almost. The lozenge (or diamond) shaped element is itself an association class which associates all connected classes. What you want it a simple association class between Student and Studies like this:
The Scholarship represents the exams passed by the students in specific studies. The association class relation is indicated by the dashed line linked to the association (which has a m-n multiplicity).
Before you get to any attributes, I don't see a correlation between the nouns in the problem statement and your classes. I would expect to see the following classes:
Student
Course
Nationality
Scholarship
I would also expect to see an association class, called CourseEnrollment, that would have the following italicized properties at the ends of the association:
Student studiedCourse [1..*] Course
Course studyingStudent [1..*] Student
That association class would have yet another association with Scholarship, called ScholarshipAward, that would have the following italicized properties at the ends of the association:
CourseEnrollment awardedScholarship [0..*] Scholarship
Scholarship receivingCourseEnrollment [0..*] CourseEnrollment
With this arrangement, a Scholarship can be awarded to a combination of Student and Course.
(I apologies in advance for my English)
I need to make a model of relation.
Normally it a thing we should do in team, but I am stuck to be alone, so I am kind of overwhelm by this
It about a school and it information concerning The Student, The Parents and the Class he want to enroll. Also they keep academic results.
I just can't get an ideal of how I could link them all and avoiding relations problems
http://i.imgur.com/fdwxH8g.jpg
First, I suggest you add a Person table to supertype Parent and Student, and move all the personal and contact information attributes to Person. You're sure to want to add additional information later, and having to duplicate everything for parents, students (and later, teachers and other school staff) gets to be a nuisance.
person (person_id PK, last_name, first_name, sex, birthday, email, address, city, phone_number, cellphone_number)
Next, do you want to record biological parents or caregivers? In schools we normally care about caregivers and their relationship to the student. To record that, you could create a relationship type table:
relationship (relationship_id PK, description)
with entries for father, mother, aunt, grandfather, fostermother, etc. You can then record the relationship between 2 persons like so:
parent (parent_id PK/FK, child_id PK/FK, relationship FK)
If you wanted to record biological parents, you could use:
bioparents (child_id PK/FK, father_id FK, mother_id FK)
with father and mother ids nullable (or decompose into separate tables for father and mother) since we're unlikely to know both parents for all students.
Finally, we get to the business at hand, students. Historical information and alumni are important in schools, so take care to model students over time, not just current students. You need to consider the time resolution for student registrations - are registrations annual, quarterly, or something else? For annual registrations, you could start with:
student (person_id PK/FK, year)
Now, what is a class? Is it something that recurs over time, or are classes with the same name in different years/quarters separate things? Can classes contain learners of different forms/grades/levels, or are they partitions of those? Is a class a grouping of students that attend multiple subjects, or a subject-specific grouping? I'm familiar with two types of classes, which could be called form classes and academic classes, but things may be different in your region of the world.
Using your class table:
class (class_number PK, name, prerequisite, formation_time)
We need to link students to it. If class membership is an annual thing, we can add to the student relation above, e.g.
student (person_id PK/FK, year, class_number FK)
Now, I just made up tables as I went along, but if you want to do this properly, you really should list/model your functional dependencies before you start making up tables. You could look into a formal modeling discipline like Object-Role Modeling, or at least write out simple logical relations in both directions:
a Student has one or more Parents
a Parent has one or more Students
a Class has a Year
a Year has zero or more Classes
a Student has a Class per Year
For non-binary relations, you don't need to write it out in every direction, but you do need to decide which combinations of attributes uniquely determine the others. For example, the combination of Student and Year uniquely determines the Class.
Anyway, that should give you a start.
I'm working since few weeks now on a project really interesting but unfortunately with a very complex background.
I already asked 3 questions :
Class Scheduling to Boolean satisfiability [Polynomial-time reduction] Final Part (here)
Class Scheduling to Boolean satisfiability [Polynomial-time reduction] part 2
Class Scheduling to Boolean satisfiability [Polynomial-time reduction]
in both of them, I get my answer (thank you again #Amit) but now arrived the final part, who will make this project useable :)
I for now can manage :
N time-intervals.
C courses.
T teachers.
S rooms.
My constraints are the follow:
2 teachers cannot be in the same room in the same time.
2 courses cannot be in the same room in the same time.
Teachers can teach only specific courses.
Some courses can happen only on specific time-intervals.
So this is for now, my result :
But here comes the final part that I want to add : I want to manage group of students, with the following constraints :
A group has only some courses to do.
2+ groups can be in the same room in the same time only for specific courses (like Magistral course for example)
Again, I success to isolate the constraint, but I have no idea on how to transform this constraint into a "time-intervals should not overlap" constraint.
Thanks in advance,
Best regards,
Since a student can only be in one place at a time:
Lectures for courses attached to the same student group should not overlap in time.
Edit:
There should be no constraint on different student groups overlapping. If you have such a constraint you should remove it!
The constraints are on courses. If you schdeule a lecture for course A, then it may not overlap a lecture for any other course for the student group(s) that attend course A. It may also not overlap any other course held by the same teacher.
So, you have a many-to-many relationship between students and courses and a many-to-many relationship between teachers and courses.
You want to schedule a number of lectures for each course with the constraint that no teacher and no student has overlapping lectures.
Regarding
2+ groups can be in the same room in the same time only for specific courses (like Magistral course for example)
If the groups may not mix, then it is not the same course (even though the subject may be the same). So if two student groups can not mix for Java, then you need to model it as two separate courses, Java group1 and Java group2.
Say we have three entities in our environment, Teacher, Student and Course.
Every teacher has (teaches) 1 or more Courses and each Course is offered by 0 or more teachers
Every Student has taken 1 or more Courses and each Course is taken by 0 or more Students
Every Teacher has 0 or more Students and each Student has 1 or more Teachers
In this relationships, each relationship could be inferred from the two others, for example to know which Students are being taught by Teacher T1, go through the relationship between Teacher and Course to see what Courses are being taught by the teacher T1, and then go through the relationship between Course and Student to see which Students has taken these Courses. These Students are the ones that are being taught by teacher T1.
So we don't need an explicit relationship between Student and Teacher, because "Conceptually" this relationship exists.
Finally the question is:
In Conceptual Design is it necessary to show all the three relationships?
And as an extra information, how would it be in Logical Design (designing database tables and relationships), should the relationship remain as an inferred relationship or should be explicitly defined ?
Here is an example,
Conceptual (using NORMA)
Teacher teaches Course
It is possible that some Teacher teaches more than one Course and that for some Course, more than one Teacher teaches that Course.
In each population of Teacher teaches Course, each Teacher, Course combination occurs at most once.
Student takes Course
It is possible that some Student takes more than one Course and that for some Course, more than one Student takes that Course.
In each population of Student takes Course, each Student, Course combination occurs at most once.
Teacher tutors Student on Course
For each Student and Course, at most one Teacher tutors that Student on that Course.
Constraints
For each Teacher and Course, that Teacher tutors some Student on that Course if and only if that Teacher teaches that Course.
For each Student and Course, some Teacher tutors that Student on that Course if and only if that Student takes that Course.
Logical
I have to create a database and I want to know what would be the best solution.
Let's say I have to store information about students and teachers.
Should I make one single table containing all the personal information (name,email,phone password) to both students and teachers?
For additional information should I keep them in separate tables as ADD_TEACHERS and ADD_STUDENTS?
You may want to create a people table for the common data like name,email etc. You can then use a primary key column in this table, and if there has to be information specific to teacher (like course_instructor, head_teacher of class), then use that unique key from people as reference in your course_information table. Do the same for students too.
It sounds like your best route is to have a separate table for teachers and students. You'll have what is called a one-to-many relationship between teachers and students: one teacher, many students.
But that only covers one semester. When you consider other semesters, you have a many-to-many relationship between students and teachers.
In the end, you're best off with at least three tables: Teachers, Students, and teacher-to-student relationship.
First thing you have to do is Map the entity relationships (ER) and its attributes.then design the database and apply the normalization strategies.
In the proposed scenario students and teachers are different entities . and find out thier relationship
ONE student ONE TEACHER
MANY Students HAVE ONE TEACHER
MANY Students HAVE MANY TEACHERs
Then check out their attributes Example - Student(Name,Class,DOB)
It depends on how you are going to use the data. If you have a lot of use cases where you are interested in "persons", regardless of role, or if you have a lot of persons who are both teachers and students, you may want to learn the gen-spec design pattern, as it applies to relational tables.
See previous discussion.