PXP is a validating XML parser for O'Caml. It strictly complies to the XML-1.0 standard. The parser is simple to call, usually only one statement (function call) is sufficient to parse an XML document and to represent it as object tree. Once the document is parsed, it can be accessed using a class interface. The interface allows arbitrary access including transformations. One of the features of the document representation is its polymorphic nature; it is simple to add custom methods to the document classes. Furthermore, the parser can be configured such that different XML elements are represented by objects created from different classes. This is a very powerful feature, because it simplifies the structure of programs processing XML documents. Note that the class interface does not comply to the DOM standard. It was not a development goal to realize a standard API (industrial developers can this much better than I); however, the API is powerful enough to be considered as equivalent with DOM. More important, the interface is compatible with the XML information model required by many XML-related standards.