Conclusion

XML data is a key element for any modern distributed and tiered system. But XML data alone is not really usable, and even when it is usable, it turns out to be not very profitable, because XML is a metalanguage that needs further instantiation and specialization.

You can think of XML as an abstract class for data description languages. Like abstract classes, you can use XML as a reference but not to perform complex tasks. So XML does matter but only if you pair it with other related technologies. In Chapter 6, we analyzed XPath as the emerging language for performing queries. I can’t say whether XPath is the definitive query tool or just a temporary technology that will soon be replaced by something else—perhaps XQuery. XPath is a key technology to enable powerful and effective data transformation, which is just what this whole chapter has been all about.

In abstract terms, transforming XML data means making data usable by actual applications and by end-users. XSLT is simply a subset of the XML style sheet language, but it probably represents the core part. This chapter provided a quick refresher course in the XSLT vocabulary of instructions and then focused on the .NET Framework implementation of the XSLT processor.

In the .NET Framework, the XSLT processor is contained in a single class—the XslTransform class. This chapter explained the programming interface of the XSLT processor and unveiled some of its internal features. We also looked at security and threading aspects and a few concrete examples of style sheet definitions and use.

With this chapter, the second part of the book, dedicated to data manipulation via XML-related standards, has come to the end. In Part III, we’ll look at a new programming aspect of XML—XML and databases. Chapter 8 in particular will discuss how to read and write data from and to databases in XML format.