XML Core Services (formerly known as MSXML, for Microsoft Extensible Markup Language or XML) is an application for processing Extensible Stylesheet Language Transformation (XSLT) in an XML file. Based on Microsoft's Component Object Model (COM), XML Core Services is essentially an application programming interface (API) to an XML parser and the XPath processor. The parser organizes the XML data into a tree structure for processing, and the processor converts the XML to Hypertext Markup Language (HTML) for display.
XML Core Services works in conjunction with Internet Explorer. The earliest version of MSXML was included on Internet Explorer 4.0, which made that version the first browser to support XML. MSXML 1.0 was a basic parser based on the Document Object Model (DOM). The current version can be used to create and validate XML documents, as well as parsing and processing them, and can make HTTP (Web site) requests and process the replies. Support is included for the World Wide Web Consortium (W3C) recommendations for XML Schema.
MSXML can be used to create, parse, and process XML documents using either DOM (memory-mapped hierarchical tree-based API) or SAX (streaming event-based API). It can be used to validate XML documents either using XSD schemas or XDR schemas. It can be used to transform XML documents using XSLT and XPath.