Reference_Syntax.contentType = “text/plain | application/x-formcalc | Mime-type
text/plain (default)
Support for other text types, such as text/html as well as scripting types such as application/x-ecmascript is implementation-defined.
When the referenced document is an image, a suitable MIME-type must be supplied for this property to tell the application that the content is an image. However, the application is free to override the supplied value if upon examining the image data it determines that the image data is of a different type. Which image types are supported is implementation-defined.
Data Model
Form Model
sourceSet Model

contentType