"XMI is a way to save UML models in XML"

Therefore, XMI can be a way to save the class-and-association structure of Simile models in XML.

Therefore, XMI can be leveraged (along with MathML, GraphML, Dublin Core...) to provide a standards-rich language for Simile models, and save a lot of work in the process.

Perdita Stevens: MOF and XMI - a mini-tutorial. http://homepages.inf.ed.ac.uk/perdita/XMI/tutslides2up.pdf

OMG XMI spec.  http://www.omg.org/technology/documents/formal/xmi.htm

Wikipedia: XML Metadata Interchange.  http://en.wikipedia.org/wiki/XMI

XSLT is used too transform XML documents into some other XML, HTML, or plain text.

XSugar enables one to define a single set of mapping rules between a non-XML and an XML format for the same information.  The rule-set can then be used in either direction.  This is a far superior approachh to requiring one to write two one-way transformations.