Entity Relationship Model

Applied IT- ER Diagrams

ER models help in understanding complex data. It also ensures easier storage of huge data in an organization. The model mainly comprises of entities, cardinality, attributes as well as relations. ER diagrams can be generated through various software models that have been developed. Although some of the software can be automatic, the type and component of data to be modeled determines the best type of software to be used (Dedhia, Jain, & Deulkar, 2015). In this case, the major entities used are student, instructor, course as well as the course offering. However, course offering is selected as one of the weak entities. Thus, it is fully dependent on the course entity.

According to the given case, the courses’ databases include prerequisites, numbers, syllabus, title as well the credit. The databases to be included for course offerings are classrooms, section number, course number, instructor’s timing, year and the semester. For the instructors’ entity in the model, identification numbers, title, name and the department will be included. Lastly, the students’ entity will be included. The database for this entity is id of the students, their programs as well as names. The ER model below includes these entities and their databases. The enrolments of students within the courses available at Hood College as well as the grades awarded to the enrolled students are also modelled in the diagram.


Two assumptions have been made. They include:

  1. There is only one class which is meeting at a specific time and at a specific place. This means that when a particular location is identified at a specific time, it is only one class that can be meeting in that place at that specific time. It will not be possible to have one class at two places at the same time. The ER model illustrated below does not show a class meeting held at varying places during the same time.
  2. The second assumption is that the database cannot guarantee accuracy in terms of having the various class meetings at a specific place during the same time. Thus, it is possible to find two classes colliding at the same place during the same time. The database is thus not accuracy in terms of the timing and meeting points. Based on these assumptions, the figure below illustrates registrar’s office ER diagram. Sid represents student id, course no. represents course number, iid represents identification number, and dept represents department.


  1. Dedhia, R., Jain, A., & Deulkar, K. (2015). Techniques to automatically generate Entity Relationship Diagram.