Diagram Conventions   «Prev  Next»

Lesson 1

Entity-relationship Diagram Conventions

At this point in the course, you know enough to translate much of what you have learned into an entity-relationship (ER) diagram. In this module, you will
  1. identify the conventions for diagramming entities and their attributes;
  2. identify the constructs used to diagram the three types of relationships (1:1, 1:N, and M:N), and
  3. identify the symbols used to indicate mandatory and optional participation in a relationship.

(Note: I use the term constructs in its generic sense, referring to a collection of images or diagramming conventions.) Finally, you will complete the course project: creating an ER diagram for Stories on CD, Inc. After completing this module, you will be able to:

Conceptual Modeling

Conceptual modeling is a very important phase in designing a successful database application. Generally, the term database application refers to a particular database and the associated programs that implement the database queries and updates. For example, a Bank database application that keeps track of customer accounts would include programs that implement database updates corresponding to customer deposits and withdrawals.
These programs include user-friendly graphical user interfaces which utilize forms and menus for the end users of the application. Thus, a major part of the database application will require the design, implementation, and testing of these application programs. Traditionally, the design and testing of application programs has been considered to be part of software engineering rather than database design. In many software design tools,
  1. the database design methodologies and
  2. software engineering methodologies
are intertwined since these activities are strongly related.
In this module, we follow the traditional approach of concentrating on the database structures and constraints during conceptual database design. The design of application programs is typically covered in software engineering courses. We present the modeling concepts of the Entity-Relationship (ER) model, which is a popular high-level conceptual data model. This model and its variations are frequently used for the conceptual design of database applications, and many database design tools employ its concepts. We describe the basic data-structuring concepts and constraints of the ER model and discuss their use in the design of conceptual schemas for database applications. We also present the diagrammatic notation associated with the ER model, known as ER diagrams in Lesson 2.

Module Objectives

  1. Define the function of an entity-relationship (ER) diagram
  2. Describe the types of entity-relationship (ER) diagrams
  3. Identify conventions for diagramming entities and attributes
  4. Identify the constructs for diagramming types of relationships
  5. Identify the symbols for diagramming types of participation
  6. Revise an ER diagram based on a final review with users
  7. Describe how to verbalize an ER diagram
The next lesson defines the function of an entity-relationship (ER) diagram, which is a diagram used during the design phase of database development to illustrate the organization of and relationships between data during database design.

Relational Database Design and Implementation