Question

a software training program is divided into training modules and each module is described by module name and the appropriate practice time. Each module sometimes has prerequisite modules. Model this situation of training programs and modules with an E-R diagram.

Answer 1

Basically, three sets of relationships exist: A COURSE may generate one or more CLASSes, an INSTRUCTOR teaches up to two CLASSes, and a TRAINEE may enroll in up to two CLASSes. A trainee can take more than one class, and each class contains many (10 or more) trainees, so there is a M:N relationship between TRAINEE and CLASS. (We must, therefore, create a composite entity to serve as the bridge between TRAINEE and CLASS.) A class is taught by only one instructor, but an instructor can teach up to two classes. Therefore, there is a 1:M relationship between INSTRUCTOR and CLASS. Finally, a COURSE may generate more than one CLASS, while each CLASS is based on one COURSE, so there is a 1:M relationship between COURSE and CLASS. These relationships are all reflected in the following E-R diagram. Note the optional and mandatory relationships: to exist, a CLASS must have TRAINEEs enrolled in it, but TRAINEEs do not necessarily take CLASSes. (Some may take "on the job training.") An INSTRUCTOR may not be teaching any CLASSes, doing research instead, but each CLASS must have an INSTRUCTOR. If not enough people sign up for a CLASS, a COURSE may not generate any CLASSes, but each CLASS must represent a COURSE

Figure Q3.8 The E-R Diagram for HEG

INSTRUCTOR TRAINEE (0,2) (0,2) teaches M 11) CLASS ENROL (10,30) generates COURSE (ON)

Answer 2

Answer 3

MARKS SUBJECTS Markld(Long) StudenFK:FR_6 Subject_Id Long) FK:FR5 D ate (Time Stamp) Mark(Integer) Subject_IdflongPK:PK_Subjects Title(Text) PK:PK_Marks t_ld(Long) TEACHERS Teacher_Id(Long) PK:PK_Teachers FirstName(Text) LastName(Text) STUDENTS SUBJ_TEACH Student_ld(Long) PK:PK_Students FirstName(Text) LastName (Text) Group_Id(Long) FK:FR 4 ST_Id(Long) PK:PK_S Subject-Id(Long) FKFR3 Teacher_Id(Long) FK:FR 2 Group_Id(Long) FK:FR_1 PK:PK Subj Teach GROUPS 艹Group-Id(Long) PKPK-Groups Name(Text)