XML uses XML namespace
XML namespaces enable the same document to contain XML elements and attributes taken from different vocabularies, without any naming collisions occurring. Although XML Namespaces are not part of the XML specification itself, virtually all XML software also supports XML Namespaces.
XML Base defines the xml:base attribute, which may be used to set the base for resolution of relative URI references within the scope of a single XML element.
XML Information Set or XML Infoset is an abstract data model for XML documents in terms of information items. The infoset is commonly used in the specifications of XML languages, for convenience in describing constraints on the XML constructs those languages allow.
XSL (Extensible Stylesheet Language) is a family of languages used to transform and render XML documents, split into three parts:
XSLT (XSL Transformations), an XML language for transforming XML documents into other XML documents or other formats such as HTML, plain text, or XSL-FO. XSLT is very tightly coupled with XPath, which it uses to address components of the input XML document, mainly elements and attributes.
XSL-FO (XSL Formatting Objects), an XML language for rendering XML documents, often used to generate PDFs.
XPath (XML Path Language), a non-XML language for addressing the components (elements, attributes, and so on) of an XML document. XPath is widely used in other core-XML specifications and in programming libraries for accessing XML-encoded data.
XQuery (XML Query) is an XML query language strongly rooted in XPath and XML Schema. It provides methods to access, manipulate and return XML, and is mainly conceived as a query language for XML databases.
XML Signature defines syntax and processing rules for creating digital signatures on XML content.
XML Encryption defines syntax and processing rules for encrypting XML content.
XML model (Part 11: Schema Association of ISO/IEC 19757 – DSDL) defines a means of associating any xml document with any of the schema types mentioned above.Some other specifications conceived as part of the "XML Core" have failed to find wide adoption, including XInclude, XLink, and XPointer.