One of the first things to get out of the way: the pico API is not RESTful. Picos don't present a collection of resources to be manipulated by GET, POST, PUT, and DELETE. However, the API does rely on HTTP and its methods for transport. If you've gotten REST as a religion, this may seem like sacrilege, but it's really a matter of using the right API for the job. RESTful APIs are great for request-response style interaction, but not so good for the evented interactions that picos support.
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Second, as I pointed out in Protocols and Metaprotocols, the pico API is really a meta-API in that describes the pattern for the API rather than the specific API itself. Put another way, every pico exposes a unique API depending on what rulesets have been installed in it.
The Sky Event API describes the event API pattern for a pico including what components are important and how those components are encoded in an HTTP method (GET or POST). The specific API for a given pico, however, depends on which rules rulesets are installed since it is rules that respond to events. Because of the event expressions in select statements, we can calculate the specific events to which a given ruleset responds. This is called salience data. This is similar to the way that RMI uses Java classes to determine the specification for the object method interactions to which a particular Java class will respond.
Similarly, the Sky Cloud API defines the patterns for queries that a pico understands. Again, this is a meta-API, since the queries that any given pico responds to depend on the modules installed. Queries are thus implementable with different code than the event processing and, in practice, tend to be much faster.
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