A WordPress thought experiment
Blog publishing systems have long implemented APIs that enable client applications to fetch and post blog entries. For historical reasons there are a variety of these APIs. Because they’re widely adopted in the blog domain, it’s pretty likely that an application that works with one blog system’s implementation of one of the APIs will work with another blog system’s implementation of the same API. But these APIs are specific to the blog domain.
What if blogs had come of age in an era when a uniform kind of API was expected? We could then ask questions of blogs in the same way we could ask questions of event services in the hypothetical example shown above, or of any other kind of service. And we could interpret the answers in the same way too.