XML, XPath, XSD, and XSLT

The last two chapters I've read in C# 4.0 in a Nutshell have been all about XML (Extensible Markup Language). Man, I am so sick of reading about XML. Luckily, I just finished chapter 11 and now I am done with it. Here are some the things I learned of in this chapter:

1. XPath is described like so verbatim at bottom of page 466: XPath is the W3C standard for XML querying. In the .NET Framework, XPath can query an XmlDocument rather like LINQ queries an X-DOM. XPath has a wider scope, though, in that it's also used by other XML technologies, such as XML schema, XLST, and XAML.
2. XSD stands for XML Schema Definition and is written in XML itself, typically saved to a .xsd document, which defines how another patch of XML should be shaped. An XSD can have an XSD in the same way a derivative can have a derivative in calculus. A XSD may be consumed to validate that a swath of XML is of the appropriate format, holding expected nodes, etc.
3. XSLT stands for Extensible Stylesheet Language Transformations and like XSD is itself XML while also being metadata for XML while typically saved out to documents with a different extension (.xslt). Use an XSLT to provide a spec for transforming one variety of XML into another. One might use an XSLT document to transform an RSS (RDF (Resource Description Framework, a W3C metadata spec) Site Summary or Really Simple Syndication) document into an XHTML (Extensible Hypertext Markup Language) document.