The difference between a wiki and a blog

The difference between a blog and a wiki appears to be that a blog is half way between a traditional WEB site and a wiki. With a blog, the blog creator has more control over the content and guests are limited to offering discussion points on the creator's posts. A wiki, on the other hand, is more open. "Guests" , if provided access, may have the opportunity to actually "edit" post made by the creator. As a result, a wiki would have a greater potential to evolve (because more people are involved in the creation process). This raises a variety of issues, positive and negatives. Is this correct? The comments above about the "discussion" nature of wikis is valid. However, perhaps this is partly due to the nature of this course (we are all learning (:-) ). If theis wiki were on a totally separate topic, astronomy perhaps, entries could be more like mini-articles.