System Interface Guide

Interface Taxonomy

The interface taxonomy classifies commitment level of an interface. The commitment level identifies who can, or how to, use the interface. Definitions:

Open specification	An interface specification that customers can use freely (build products that use this implementation of the interface). Others are free to provide alternative implementations without licensing or legal restrictions.
Closed specification	An interface specification is not published.
Compatible change	A change to an interface or its implementation that has no effect on previously valid programs.
Incompatible change	A change to an interface or its implementation that makes previously valid programs invalid. This might include bug fixes or performance degradation. This does not include programs that depend on unspecified "artifacts of the implementation."

Standard Classification

Specification	Open
Incompatible Change	Major release (X.0)
Examples	POSIX, ANSI-C, Solaris ABI, SCD, SVID, XPG, X11, DKI, Ethernet

Standard interfaces are those whose specification is controlled by a group outside of Sun. This includes standards such as POSIX and ANSI C, as well as industry specifications from groups such as X/Open, the MIT X-Consortium, and the OMG.

Public Classification

Specification	Open
Incompatible Change	Major release (X.0)
Examples	Sun DDI, XView, ToolTalk, NFS protocol, Sbus, OBP

These are interfaces whose specification is completely under Sun Microsystem's control. The specification of these interfaces and will remain compatible with the published specification.

Obsolete Classification

Specification	None
Incompatible Change	Minor release (.X.0)
Examples	RFS

An interface no longer in general use. An existing interface can be downgraded from some other status (such as Public or Standard) to Obsolete through a standard program to communicate the change in commitment to customers.

A change in commitment requires one year's notice to the customer base and the Sun product development community of the intended obsoleting of the interface. A full year must elapse before delivering a product that contains a change incompatible with the present status of the interface.

Acceptable ways to notify customers includes letters to customers on support contracts, release notes or product documentation, or announcements to customer forums appropriate for the interface in question.

The notice of obsolescence is considered to be "public" information in that it is freely available to the customers. This should not require specific actions to "publish" the information, such as press releases or similar forms of publicity.