XPath - XML Pattern Matching
XPath is a language for addressing parts of an XML document.
XPath was designed to be used by both XSLT and XPointer.
XLink - XML Linking Language
The XML Linking Language (XLink), allows elements to be inserted
into XML documents in order to create links between XML
resources.
XPointer - XML Pointer Language
The XML Pointer Language (XPointer), supports addressing into
the internal structures of XML documents, such as elements,
attributes, and content.
DTD - Document Type Definition
A DTD can be used to define the legal building blocks of an XML
document.
Namespaces
XML namespaces defines a method for defining element and
attribute names used in XML by associating them with URI
references.
XSD - XML Schema
Schemas are powerful alternatives to DTDs. Schemas are written
in XML, and support namespaces and data types.
XDR - XML Data Reduced
XDR is a reduced version of XML Schema. Support for XDR was
shipped with Internet Explorer 5.0 when XML Schema was still a
working draft. Microsoft has committed full support for XML
Schema as soon as the specification becomes a W3C
Recommendation.
DOM - Document Object Model
The DOM defines interfaces, properties and methods to manipulate
XML documents.
XQL - XML Query Language
The XML Query Language supports query facilities to extract data
from XML documents.
SAX - Simple API for XML
SAX is another interface to read and manipulate XML documents.
W3C Recommendations
The World Wide Web Consortium (W3C) was founded in 1994 to lead
the Web by developing common WWW protocols like HTML, CSS and
XML.
The most important work done by the W3C is the development of
Web specifications (called "Recommendations") that describe
communication protocols (like HTML and XML) and other building
blocks of the Web.