I just had a cool idea. Usually, people run HTML templating engines on GET. They fetch some data, load an HTML template, and then mash the two together. My idea is to instead run the templating engine on PUT. The body of the PUT would have the data to be templated. The URL that was PUT to would determine which template to use. The response from the PUT would contain the fully templated output, equivalent to what the client would get by doing a GET to that url at any point afterwards.
