What is the solution? Depends on what you want to do.
- If you have control over server-side of the system, you need to incorporate certain kludges to support Flash restrictions. For example, provide crossdomain policy-file, map some header or URL to method PUT and DELETE, return 200 success response with message body containing actual error code (e.g., 404 vs 405 vs 501) or headers. Any of these techniques looks like a hack at best.
- If you have control over the client, you can use an existing third-party RESTful client library in ActionScript. However, be prepared to provide a crossdomain policy-file or incorporate a proxy. Alternatively, you can also perform some Flash Player-specific translations on the fly in your proxy.
- You cannot build a general purpose RESTful web application (server-side) and expect Flash Player application to use them. You will need to be Flash Player-aware.
- You cannot build a general purpose Flash application (client-side) to use an existing RESTful web service without additional dependencies and network elements (proxies).
- It looks like HTTP+REST won't really be able to solve all the problems in ActionScript for Flash Player without Adobe's blessings, e.g., incorporate full HTTP stack in the Flash Player or provide a different way other than crossdomain to do authentication of scripts.