Difference between XML and XMI?

Question

Can some one shed some light on the difference between XML and XMI? Can XMI be used in place of XML?

Answer 1

The XML Metadata Interchange (XMI) is an Object Management Group (OMG) standard for exchanging metadata information via Extensible Markup Language (XML).

XMI integrates four industry standards:

XML - eXtensible Markup Language, a W3C standard. 
UML - Unified Modeling Language, an OMG modeling standard. 
MOF - Meta Object Facility, an OMG language for specifying metamodels. 
MOF Mapping to XMI 

http://en.wikipedia.org/wiki/XML_Metadata_Interchange

So XMI is a specific application of XML.