There is simply no set of necessary or sufficient criteria for determining whether some program is indeed a software agent. The ``definition'' varies widely, as do approaches to building agents. However, we can look for some general agent characteristics by examining some typical (and not necessarily mutually exclusive) approaches.
We note here that no other software agent system (of any flavor) that we know of has an automated distribution mechanism like SodaBot's. In fact, personal communication with several of the researchers below indicates that this currently poses some difficultly, because few people outside of their research groups can make use of their agents.