A full-use guideline has the highest support level, so it is the most protected from incompatible modification or deletion. There should rarely be a need to remove a full-use guideline, or make incompatible modifications to it. This provides time for applications to be altered to deal with a different guideline, and for implementations to prepare for the change. Assuming the review concludes that this change is appropriate, the guideline in Release 1.3 still has full-use status, but is accompanied by a warning. The warning states that the guideline is scheduled for modification after Release 1.4, and describes the modified behavior.
Application developers can now allow for either the original or the modified guideline.
Release 1.4 contains the same warning. Release 1.5 provides the modified definition only. There are several reasons why OSF classifies guidelines as trial use instead of full use. A guideline may be under consideration for inclusion in a de jure standard and so may possibly change as a result of the standards process. Or, OSF may perceive that the guideline is new compared to other included guidelines and, therefore, the implementation and use of the guideline may suggest revisions in its definition.