10.5. Summary

To work with XML, a basic understanding of the XML document, schema, and style sheet is required. An XML document, which is a representation of information based on XML guidelines, can be created in numerous ways. The XmlSerializer class can be used when the data takes the form of an object or objects within a program. After the XML document is created, a schema can be derived from it using the XML Schema Definition (XSD) tool. Several classes use the schema to provide automatic document validation. The usefulness of XML data is extended by the capability to transform it into virtually any other format using an XML style sheet. The style sheet defines a set of rules that are applied during XML Style Sheet Transformation (XSLT).

XML data can be processed as a stream of nodes or an in-memory tree known as a Document Object Model (DOM). The XmlReader and XmlNodeReader classes provide an efficient way to process XML as a read-only, forward-only stream. The Xml Reader, XPathDocument, and XmlDataReader classes offer methods for processing nodes in the tree structure.

In many cases, data extraction from an XML tree can be best achieved using a query, rather than traversing the tree nodes. The XPath expression presents a rich, standardized syntax that is easily used to specify criteria for extracting a node, or multiple nodes, from an XML tree.