Defining a resource
Fielding's dissertation describes a Resource as:
"Any information that can be named" ... "a document or image, a temporal service (e.g. “today’s weather in Los Angeles”), a collection of other resources, a non-virtual object (e.g. a person), and so on. In other words, any concept that might be the target of an author’s hypertext reference must fit within the definition of a resource. A resource is a conceptual mapping to a set of entities, not the entity that corresponds to the mapping at any particular point in time."
Defining a resource is both a science and an art. It requires both domain knowledge and API architectural skills. The following points detailed below serve as a checklist that may help you determine the shape of your resource, what data it should contain, and how it should be presented to consumers of your API.