When you import or export Enterprise Architect packages to XMI, the import or export process can be validated using a Data Type Definition (DTD). The XML parser uses this document  to validate the correctness of the model and to check that no syntactical errors have occurred. It is always best to use a DTD when moving packages between Enterprise Architect models as it ensures correctness of the XMI output, and prevents attempted imports of incorrect XML.

Several DTDs for XMI/UML exist. The OMG defines a standard UML1.3 DTD for use in XMI 1.1.  Enterprise Architect uses an extension of this with some additional element extensions for non-standard UML types, such as testing details.

Whenever you read an XML file, the XML parser looks in the current directory for the DTD - if specified - using the DOCTYPE element in the XML file. If the parser cannot find the DTD, it records an error and aborts processing. You must ensure the UML_EA.DTD file is in the current XML output path (generated by default).