Clarification on mimeAttributes vs clientAttributes

Does anyone have a reason for having both of these? If so is there a
difference?

  
http://docs.oasis-open.org/wsrp/v2/wsrp-2.0-spec-os-01.html#_UploadContext

    

  
    
mimeAttributes: 
Attributes received from the client (e.g. http headers, other
attributes relative to the upload file, etc.)  that are not
represented elsewhere within the protocol.

  
  
http://docs.oasis-open.org/wsrp/v2/wsrp-2.0-spec-os-01.html#_ClientData

  
    
 clientAttributes:
Attributes received from the client (e.g. HTTP headers) which are not
represented elsewhere within the WSRP protocol and which the Consumer
is choosing to supply to the Portlet.  When this
structure is being supplied to the getResource operation,
Consumers SHOULD supply the same set of items which would have been
supplied using the HTTP proxy method of serving the resource.

  

Thanks,

Nate