The rating system defines five levels of proxies: circuit-layer, traffic-aware, command-aware, content type-aware and policy-aware proxies. These definitions are pretty loose. This is intentional. Vendors are expected to provide some argument as to why they their support for a particular protocol is at a given level. A person reviewing firewalls should read the vendor's arguments, not their marketing glossies and make their own decisions. As such, this should perhaps be called a glossary.