hi @Aljoscha: regarding message types, with our current approach where message content is an map with a type field, this means the content is self-describing, as in the content includes information about the type. compare to blobs which are not self-describing, we embed information in the reference links about the media type, size, etc, which means if you have a blob you don't always know the type (although as with file types on linux we can usually compute the type from magic numbers in the content). in keeping with your desire to remove the map for message content, maybe message content is a tuple with (type, content), which could be represented similar to multiformats. not sure if this is a worthwhile approach but came up in my mind so thought i'd share.