wolfkden wrote:

I reinstalled using 1.16.0, all is well, I do not know whst went wrong but possibly some other extensions I installed such as custom Nav corrupted the ExportRDF. I also noticed a lot of modifications in the skin code in mediawiki release 1.16

The problem might have been due to empty lines at the beginning of the RDF export. This is caused easily in PHP if loaded php files contain an empty line after a closing "?>" tag. This can be caused by any of the loaded files, even if completely unrelated to SMW or the export function. Even LocalSettings.php can cause this.

The modern way of preventing this is to not have closing ?> at the end of PHP files at all: no recent MW extension should have closing PHP tags at the end of its files, but of course there can always be black sheep (or simply very aged LocalSettings.php that have survived from the age of closing tags).

Anyway, this is not an SMW bug and it is not possible for SMW to fix it (the empty lines are sent to the browser even before SMW starts the export; SMW cannot take them back or even check if they are there).