ER/Studio - Embarcadero Technologies Product Documentation

ER/STUDIO OVERVIEW > DEVELOPING A DATA MODEL
The basic idea behind entity-relationship modeling is this: everything in a business can be generalized into an abstract
or archetypal ideal, which we call an entity. These entities have certain characteristics or attributes. These entities also
are related to one another through actions that each entity performs on one or more of the other entities. We call these
actions, relationships.
In determining the relationship between each of the entities in a data model, you will define a number of business
rules. Business rules define your business and how you run it. For instance, you know that to be useful, each
employee ID, project ID, and department ID must be unique. While you could use the social security number as the
employee ID, you might want to keep the ID short and more easily sorted. More complex issues to consider are
questions such as, “How are we to connect employees, projects, and departments so that we minimize data
redundancy and maximize our reporting capabilities?” The answers to this and other questions form the rules by which
you run your business.
Attribute definitions can be used along with relationships to determine or enforce business rules. You can define a
particular set of valid values for any attribute of any entity. For example, you can define a valid range of salaries for a
subset of employees for an attribute called Salary. This set of values is known as a domain.
The Dimensional Model: Dimensional modeling is generally agreed to be the most useful for representing
end-user access to data. Where a single entity-relationship diagram for an enterprise represents every possible
business process, a dimensional diagram represents a single business process in a fact table. ER/Studio can identify
individual business process components and create the DM diagram for you.
You can create a dimensional diagram by starting with a logical model, by reverse-engineering, by importing an SQL
or ERX file, or by adding a new physical model.
Developing a Data Model
The following overview outlines the ER/Studio data model development process, which is an iterative process.
Starting With a Basic Data Model
You can start from scratch or reverse engineer an existing database.
Creating a Basic Data Model
1 Create a new data model; Creating and Working With Data Models.
2 Add entities; Creating and Editing Entities.
3 Define entity attributes; Creating and Editing Attributes and Columns.
4 Establish relationships between entities; Working with Relationships.
5 Assign keys; Creating and Editing Keys.
EMBARCADERO TECHNOLOGIES > ER/STUDIO® 8.0.3 USER GUIDE 36