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The interface taxonomy classification provided here is for guidance to developers and users of interfaces. The classification guides a developer to declare the targeted audience or users of an interface and also its stability.
Hadoop adopts the following interface classification, this classification was derived from the OpenSolaris taxonomy and, to some extent, from taxonomy used inside Yahoo. Interfaces have two main attributes: Audience and Stability
Audience denotes the potential consumers of the interface. While many interfaces are internal/private to the implementation, other are public/external interfaces are meant for wider consumption by applications and/or clients. For example, in posix, libc is an external or public interface, while large parts of the kernel are internal or private interfaces. Also, some interfaces are targeted towards other specific subsystems.
Identifying the audience of an interface helps define the impact of breaking it. For instance, it might be okay to break the compatibility of an interface whose audience is a small number of specific subsystems. On the other hand, it is probably not okay to break a protocol interfaces that millions of Internet users depend on.
Hadoop uses the following kinds of audience in order of increasing/wider visibility:
Hadoop doesn't have a Company-Private classification, which is meant for APIs which are intended to be used by other projects within the company, since it doesn't apply to opensource projects. Also, certain APIs are annotated as @VisibleForTesting (from com.google.common .annotations.VisibleForTesting) - these are meant to be used strictly for unit tests and should be treated as "Private" APIs.
Stability denotes how stable an interface is, as in when incompatible changes to the interface are allowed. Hadoop APIs have the following levels of stability.
How will the classification be recorded for Hadoop APIs?