Hour3.Defining Data with DTD Schemas

Hour 3. Defining Data with DTD Schemas

Computers are not intelligent. They only think they are.

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One thing XML aims to solve is human error. Because of XML's structure and rigidity as a language, there isn't much room for error on the part of XML developers. If you've ever encountered an error at the bank (in their favor!), you can no doubt appreciate the significance of errors in critical computer systems. XML is rapidly being integrated into all kinds of computer systems, including financial systems used by banks. The rigidity of XML as a markup language will no doubt make these systems more robust. The facet of XML that allows errors to be detected is the schema, which is a construct that allows XML developers to define the format and structure of XML data.

This hour introduces you to schemas, including the two major types that are used to define data for XML documents. The first of these schema types, DTDs, is examined in detail in this hour, while the latter is saved for a later lesson. This hour explores the inner workings of DTDs and shows you how to create DTDs from scratch.

In this hour, you'll learn

• How XML allows you to create custom markup languages

• The role of schemas in XML data modeling

• The difference between the types of XML schemas

• What constitutes valid and well-formed documents

• How to declare elements and attributes in a DTD

• How to create and use a DTD for a custom markup language