Actually, content was the whole point behind the protocol. We were trying to solve a class of problems, all driven by content requirements. Examples are the SEC's EDGAR database, a variety of other "deep wells", and a class of problems ranging from mapping network topology to creating personalized "maps" (views) of the Internet. See here for more on the philosophy behind the content requirements.

The protocol emerged from long discussions about how to solve these content problems. We tried as hard as possible to reuse existing protocol infrastructure, but quickly found that there were no protocols that handled the metadata problems we were trying to attack.

The (IMHO) brilliant thing Marshall did was to build two levels into the solution. BXXP is the general-purpose framework that was used for the Simple Exchange Profile application we were going for in the first place. The nice thing was that BXXP works for a broad range of other applications, such as asynchronous messaging.

The bottom line is why reinvent the wheel more than once?

Carl