XWiki XML Files should follow these rules:

• Have a proper License header
• Use xwiki:XWiki.Admin as the author, contentauthor and creator
• Use 1.1 as the version
• Use false for minoredit
• Have an empty defaultLanguage entry
• Have an empty comment entry
• Indent the XML using 2 characters for indentation
• Set a mime type for attachments
• Must not include date, creationDate, contentUpdateDate or attachment date fields

This cleanup can be done automatically, by using the "mvn xar:format" Maven command, see Generating a XAR for your build.