Sample Information System Functional ERD
A functional Entity Relationship Diagram helps system designers visualize the relationships among entities comprising a system. This weekly paper documents an ERD built from the requirements presented in a scenario comprising the functionality for a university data system to track concerts.
This system comprises five entities with their associated attributes. An entity’s attributes describe the entity and help to distinguish that entity from another entity of similar type. The five entities and attributes for the UCIS are as follows:
• venue with a name attribute
• concert with a date attribute
• conductor with last name and first name attributes
• music with a composition-date attribute
• composer with last name and first name attributes
Universal Modeling Languagu
The interactions between these entities are determined by the business rules for the system. The business rules specified by the university are as follows:
• A venue has a concert.
• A conductor conducts a concert.
• A concert includes a piece of music.
• A composer composes a piece of music.
Developers need to understand the interaction between the entities in order to design a functional system. Modeling the system provides the visualization to help ensure the developers and stakeholders understand these interactions. A functional Entity Relationship Diagram (ERD) is one type of model that serves this purpose. “ER diagrams have three core constructs – entities, attributes, and relations that are combined to specify a problem’s elements and their relationships” (Pfleeger and Atlee, 2006, p. 158).
This representation of an ER presents entities as rectangles, attributes as ovals connected to the entities, and relations as diamonds connected between the entities. The UCIS Functional ERD shown in Figure 1, below, depicts the University Concert Information System.
As shown in the diagram, each of the entities is visually presented along with the attributes that describe them. The relationships between the entities are clearly visible. Developers and stakeholders can easily come to agreement concerning the functionality of the system by referring to the diagram.
The successful design of a system depends on communication between developers and stakeholders, and understanding of the system requirements by all concerned parties. Diagrams and models like the ERD facilitate development by aiding that communication and understanding.
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