Simple Entity Relationship Model

The Simple Entity Relationship Model pattern creates elements and a diagram that describe the things of interest in a domain and the way they relate to each other. Entities are modeled as rectangles and their attributes (properties) are modeled as separate elements using an ellipse. Relationships are created between the Entities using a diamond shaped marker of a solid line. They are often used as a precursor to more formal and rigorous database modeling.

Figure 1. Shows three entities related by two named relationships. One of the Entities has three Attributes and another two.

Discussion
The purpose of the pattern is to allow information architects and business and information analysts to create visual representations of the important 'things' (Entities) in a domain of study or discourse. They are typically used as a conceptual data model or a precursor to the more formal data models used to describe a relational database management system.  

It is typically created very early in the research or discovery phase of an initiative as it forms a foundation upon which almost every other model is built. It will however be refactored, embellished or pruned during subsequent phases as more knowledge surfaces or the scope of an initiative is defined.  

The following is a list of some things you may want to do when working with this pattern.
·	Change the name of the Entities, their Attributes and other properties such as tagged values.
Create additional Entities including Attributes and add relationships. 

The following is a list of some of the next steps available when applying the pattern.
·	Create traces from other models as they are developed to the Entities in the Entity Relationship Model.
Create sub-models by creating smaller diagram that focus on just one facet of the larger model. This can be achieved by simply selecting a group of elements on the main diagram and pasting them onto a newly created diagram.
Create a transformation to transform the entire model or part of it to a logical or physical data model for a specific relational database management system.

Reference
The following help topics will assist you learn about how to work with this pattern.
Entity Relationship Diagram as a Tool
Entity Relationship Diagrams
Model Transformation

The following are some of the tools that will be helpful when working with this pattern.
Specification View
The Specification View can be used as a way of working with the Components and Interfaces particularly when there are a large number of elements as is typically the case when describing a system of any appreciable size. For more details see the Specification View help topic
Relationship Matrix
The Relationship Matrix provides a spreadsheet like view of two groups of elements and the relationships that exist between them. It can be a used as a powerful analysis mechanism to visually indicate how elements are related to each other and to discover which elements are missing relationships. For more details see the Relationship Matrix  help topic.
Traceability Window
The Traceability Window automatically displays the relationships that exist between Use Cases and other model elements including up-process and down-process elements. The traceability tree view can be conveniently expanded to see deeper relationships and elements displayed in the window can be located in all diagrams in which they appear. For more details see the Traceability Window  help topic.
Document Generator
The Document Generator is a powerful facility in Enterprise Architect that allows a Database Engineer or other stakeholder to create high quality corporate or technical documentation directly from the model, suitable for internal or external audiences. For more details see the Documentation help topic.
Model Transformation
The Model Transformation facility allows a modeler to transform a Conceptual data model to a Logical data model and in turn a Logical Data Model to a Physical Data Model. The transformations are driven by user-defined or built-in templates. This facility will save time and effort and reduce the possibility of errors.
Database Builder
The Database Builder is the primary tool for working with data models in Enterprise Architect. It is a purpose built tool that provides a custom interface for performing database-related modeling tasks. New data models and databases can be created or existing ones reverse engineered into the tool. Connections can be made to live databases including any number of environments such as Production, Pre-Production, Test and Development allowing incremental updates to the models and databases. Once the pattern is imported into a model the data models can be loaded and opened in the Database Builder.

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