Chapter 13: Data Modeling and XML

Overview

This chapter is left until the end of this book because it ties together the conceptual application and database aspects of XML. Document Type Definition (DTD) is an older form of XML Schema Definition (XSD). However, it is important to cover both DTD and XSD, partially because DTD is less complex than XSD. Less complexity can help to demonstrate concepts gradually. Additionally, DTDs are still in use so it cannot really be avoided.

It is assumed throughout this book that you are at least familiar with relational database modeling, in terms of tables, fields, and relationships between tables. As you read through this chapter, you should see the distinct similarity between relational database tables and fields, when compared to that of DTD and XSD. One of the primary reasons for the existence of DTD and XSD is for validation of XML data against an existing table structure in a relational database model. If you remember, Chapter 6 included an extensive section about using XSD to map between XML and relational tables. So, another purpose of the existence of DTD and XSD is for an automated mapping process between XML and relational database data. Of course, this type of processing can be performed using XSL, as already shown in this book. However, it is essential to understand that DTD and XSD can be used to achieve the same result.

There are no Try It Out sections in this chapter as the content of this chapter is primarily concep tual, but also introductory with respect to native XML database standards.

In this chapter you learn about:

• The Document Type Definition (DTD)

• Using non-standard XML syntax in DTD scripts

• DTD elements, attributes, and entities

• Using entities to allow for substitution in DTD scripting

• The XML Schema Definition (XSD)

• Using standard XML structure and syntax in XSD

• The more advanced capabilities of XSD in comparison to DTD