KDDML (KDD Markup Language) is a middleware language and system designed to support the development of final applications or higher level systems which deploy a mixture of data access, data preprocessing, extraction and deployment of data mining models. A KDDML language query is an XML-document where XML tags corresponds to operations on data/models, XML attributes correspond to parameters of those operations and XML sub-elements define arguments passed to the operators. The core of the KDDML system is a KDDML language interpreter with modularity and extensibility requirements as the main goals.