Modifying a Database Design in Visio - Assignment Example

Entity relation diagrams are defined as a graphical representation of an information system that shows relationships between people, objects, events, and places within the information system. They enable designers to express their understanding of how the intended database will do, and how it might work and communicate about the database through simple language.

Visio diagram help visualizes the database design since they make use of entity classes and attributes. An object type is identified by a noun and in some cases, it may be a strong or weak entity class. A Strong object type is represented by a triangle and a weak entity class by a triangle inside another triangle. Attributes collectively represent the object class. Attributes by themselves are meaningless and cannot clearly define themselves. In the Visio diagrams, they are usually symbolized by an oval.

Attributes are what is stored in the database hence giving a clear view of how the database would appear. Example: student has a student Id, name, and course. In the above example, the student is the entity class and the student Id, name and course are attributes. Some attributes have a primary key. The key is preferably composed of only a single attribute, but in some cases, more than one.

The final element of the entity relationship diagram is the relationship. Entities have relationships between them and should be represented where appropriate. Relationships are represented by a diamond and two connecting lines.

1. b) Assumptions made about business rules in order to create a Visio diagram and its relations.

A business rule is a statement that imposes some constraint on some particular aspect of the database. You base a business rule based on the organization's views and usage of its data, which you determine from the way in which the body performs or conducts its affairs.

Ways of doing things are unique and have different requirements in each group. An example is a club having more than one student and the student not being a member of more than one club. Therefore, there is a constraint on the student’s membership in a given number of clubs (Andreescu & Mircea, 2012).

Our Visio diagram has assumed some of the following business rules:

First, the course can have more than one student partaking in it and more than one student can be part of the course. It means, many students will be taking a course, and a student can also do many courses.

Secondly, more than one student can be taught by an instructor, and only one instructor can teach many students. It means that only one teacher can teach students and many students in the course can be taught by one teacher.

Finally, more than one tutor can teach a course, and a tutor can teach many courses. It means that more tutors can teach a course, and a tutor can teach also many courses.