How This Book Is Organized | Beginning XML Databases (Wrox Beginning Guides)

One of the biggest challenges in writing a book such as this is to maintain focus on the subject at hand. Of course, one has to introduce some of the basic facts of XML and database technology in order to achieve a sensible merging of these two very widely scoped topics. This is precisely why this book focuses on XML in the first three chapters. Chapter 4 focuses on relational database technology by introducing the basics of SQLso important for understanding database structure and reading a relational database. Chapters 5 and 6 attempt to begin the merging process of XML and databases by describing the ways that Oracle and SQL Server are including XML capabilities. Chapter 7 attempts to demonstrate not only the platform-independence capability of XML, but also the database vendor-independence of XML. Chapters 8 and 9 go back into database technology. Chapter 8 explains XML as the equivalent of an object database model. Chapter 9 presents XML, and any XML document, each as being a database in itself. Chapters 10 through 13 describe some of the most advanced features of XML, further expanding the concept of an XML document as a database. Chapter 14, the final chapter in this book, wraps it all up by describing some applications, tools, and implementations of XML in modern industry.

Within most chapters are Try It Out sections where you get to try out various concepts, summary sections, and exercise sections at the end. The entire book includes as much example material as possible. I have attempted, wherever possible, to reuse the same data set throughout the entire book in order to maintain consistency and provide a sense of reality. The objective is to include as much diverse material as possible. This should help to give a better overall understanding of the topics at hand.

This book contains a glossary, which allows you to look up terms rapidly and avoid having to page through the index, and the entire book, searching for explicit definitions of frequently used terms.

Chapter 1 , What Is XML? This chapter gives you a brief summary of eXtensible Markup Language (XML). XML is extensible or changeable . HTML (HyperText Markup Language), on the contrary, is a non-extensible language.
Chapter 2 , The XML Document Object Model (DOM) : This chapter tells you all about the XML Document Object Model (XML DOM). The XML DOM allows complete dynamic access to all the bits and pieces within an XML document. The XML DOM allows programmatic change to an XML document at run-time.
Chapter 3 , Extending the Power of XML with XSL : This chapter covers eXtensible Style Sheets (XSL). XSL is used to template and filter XML data. This chapter briefly touches on using database data directly.
Chapter 4 , Relational Database Tables and XML : This chapter examines how data is accessed within a relational database using Structured Query Language (SQL). SQL is a language used for reading data from a relational database. Specialized commands are used to change data: INSERT , UPDATE , and DELETE .
Chapter 5 , Oracle Database and XML : There is immense capability in Oracle Database and Oracle SQL for utilizing the power of XML. This chapter covers XML only as directly related to Oracle Database and Oracle SQL. You examine how XML documents can be created, accessed, and manipulated directly from within an Oracle database. You will be presented with various specialized techniques and facilities available in an Oracle Database, including embedded XML data types.
Chapter 6 , SQL Server and XML : There is also immense capability in SQL Server database for utilizing the power of XML. This chapter covers XML only as it directly relates to SQL Server. You examine how XML documents can be created, accessed, and manipulated directly from within a SQL Server database. You are presented with various specialized techniques and facilities available in a SQL Server database, including embedded XML data types.
Chapter 7 , Using XML in Heterogeneous Environments : The structure of XML documents is an established and widely accepted standard. XML is also very easy to use and understand. Passing XML documents between different database engines, different operating systems, and different hardware platforms is easy! This chapter demonstrates how to transfer XML easily between different computer architectures. One of the central tenets of XML is to allow for sharing of data without regard to whatever is at either end of a transfer.
Chapter 8 , Understanding XML Documents as Objects : This chapter is included to give you an understanding of the object data model because XML document structure is hierarchical. XML documents can be flat structured but best utilize XML when they are hierarchically structured. XML document structure is similar to that of object data model structure.
Chapter 9 , What Is a Native XML Database? Chapters 5 and 6 cover specifics of Oracle and SQL Server databases respectively. This chapter attempts to conceptually refine some of the details covered in those chapters, and also to expand on much of what is covered in previous chapters. This chapter begins the process of describing native XML databases. A native XML database describes an XML document as a database by itself.
Chapter 10 , Navigating XML Documents Using XPath : This chapter briefly covers XPath technology, including XPath 1.0 and XPath 2.0. XPath is a specialized expression language, used to parse through XML node hierarchies and retrieve chunks of data from XML documents. XPath is a major part of the scripting language eXtensible Style Sheet Transformations (XSLT). XSLT is the transformation subset of XSL. Many of the other tools, such as XPointer and XQuery, are based on XPath.
Chapter 11 , Reading XML Documents Using XQuery: XPath is used to navigate through XML documents, based on an absolute or relative position of a node in an XML document. XQuery makes extensive use of XPath expressions in order to build XQuery query commands. XQuery is to XML as SQL is to relational databases. So, XQuery is used to read XML documents. XQuery is designed to query anything appearing as XML data, even XML data type structures (or otherwise ) and XML stored in a database as XML data types.
Chapter 12 , Some Advanced XML Standards : Many of the advanced standards of XML are not essentially database specific, but more front-end application coding specific. Where your database stores your data, your front-end application is made up of the screens you use to communicate with that database. Advanced XML standards such as XLink, XPointer, and XForms may not at first seem quite relevant to this text. However, in order to do XML justice , I have to at least touch on both database and application XML capabilities. And as you shall see in this chapter, front-end applications can sometimes be very closely related to database content. The fact is, XML is often generated dynamically from data. This generated XML often includes use of tools such as XLinks, XPointers, and XForms.
Chapter 13 , Data Modeling and XML : This chapter ties together the conceptual application and the database aspects of XML. Document Type Definitions (DTD) and XML Schema Definitions (XSD) can both be used to impose structure onto XML data. The overall message of this chapter is critical to the understanding of the confluence of XML and relational databases. This chapter conveys the concept that a rigid structure can be applied to any XML document. This is very much the same conceptually as tables and schemas that apply rigid structure to a relational database. The result is that a relational database model can be applied to any XML document that conforms to the logical structure of that relational database model. XML documents and relational databases can be fit together structurally using DTDs and XSDs.
Chapter 14 , Applying XML Databases in Industry : The purpose of this chapter is to give you, the reader, a brief picture of the how and what of XML use in industry today. What is being used? What is it being used for? How is it being used? What are some of the products? What are their basic capabilities? This book focuses on concepts with respect to native XML databases. It does not provide details for any specific native XML database. Additionally, both Oracle and SQL Server databases include an XML data type. This makes both of these databases quite capable as native XML databases through the application and use of their contained XML data types.