Extensible markup language (XML) is a new powerful technique for Web and Internet development. It is a method of defining structured data in a text file. XML is expected to do for data what HTML has done for Web pages. XML's stiength lies in its simplicity to represent data and knowledge. It can maintain hierarchical structures encountered in many systems including assemblies and disassemblies. It can also be well integrated with Java, and its Java beans. Its strength lies in its flexibility to adapt to any knowledge domain because it is a metalanguage. It is used to develop modeling languages that are tailored to specific knowledge, and specific data structures and hierarchies. This paper presents an overview of XML, followed by a proposal of an XML-based knowledge representation model for disassembly planning. An example is used to demonstrate the capabilities ofthe proposed XML model.