ERwin Methods Guide

Preface

Welcome to data modeling with ERwin. If you have never seen a model before, the ERwin Methods Guide will help you understand what a model is, and what it is good for. If you already have some experience with data and data models, you know how useful they can be in understanding the requirements of your business. A model can help if you are designing new information systems or are maintaining and modifying existing ones.

Data modeling is not something that can be covered in a lot of detail in a short document like this one. But by the time you have read it, you will understand enough, even if you are just a beginner, to put ERwin’s methods to work for you. Overall, the ERwin Methods Guide has the following purposes:

♦To provide a basic level of understanding of the data modeling method used by ERwin that is sufficient to do real database design.

♦To introduce some of the descriptive power and richness of the IDEF1X and IE modeling languages supported by ERwin and to provide a foundation for future learning.

♦To provide additional information that lets you to better understand ERwin’s modeling features.

This document covers the methods of data modeling supported by ERwin, which include:

♦IDEF1X. The IDEF1X method was developed by the U.S. Air Force. It is now used in various governmental agencies, in the aerospace and financial industry, and in a wide variety of major corporations.

♦IE (Information Engineering). The IE method was developed by James Martin, Clive Finkelstein, and other IE authorities and is widely deployed in a variety of industries.

Both methods are suited to environments where large scale, rigorous, enterprise-wide data modeling is essential.

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ERwin Methods Guide

Intended Audience

This manual is intended for:

♦Novice database designers and data modelers — as a primer on data modeling, and as a guide to using the ERwin methods.

♦Experienced data modelers and applications developers — as a guide to IDEF1X and IE data modeling in ERwin.

♦Experienced IDEF1X or IE users — as a guide to the features of IDEF1X and/or IE supported by ERwin, and the mapping between these methods.

About this Guide

This document contains seven chapters, an appendix, a glossary, and an index:

♦Chapter 1 describes data modeling, provides a sample methodology for creating a data model, and the benefits of modeling in ERwin.

♦Chapter 2 describes the creation of an entity-relationship diagram (ERD) and explains both the process and validation of the model. This chapter also introduces the ideas of entities, attributes, and relationships.

♦Chapter 3 explains the concept of keys, including candidate keys, primary and alternate keys, inversion entries, migration of foreign keys, and the use of rolenames.

♦Chapter 4 explains the importance of creating accurate names and definitions for entities, attributes, and rolenames in the logical model.

♦Chapter 5 provides additional information about entity relationships, including relationship cardinality, referential integrity. This chapter also describes additional relationship types, such as many-to-many, n-ary, recursive, and subtype relationships.

♦Chapter 6 defines normalization and the six normal forms of database design. This chapter also provides solutions to a number of common design problems, and describes ERwin’s support for normalization.

♦Chapter 7 describes physical model constructs and the creation of the physical model from a logical model in ERwin.

♦Appendix A describes the types of dependent entities, including characteristic, associative, designative, and subtype entities, and their use in a logical model.

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Typographical Conventions

The ERwin Methods Guide uses some special typographic conventions to identify ERwin user interface controls and key terms that appear in the text.

Related Documentation

The ERwin documentation set includes the following print and online manuals:

♦ERwin Online Help

♦ERwin Methods Guide (this guide)

♦ERwin Reference Guide

♦ERwin Features Guide

♦ERwin Workgroup Modeling Guide

♦Logic Works RPTwin User’s Guide

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