Stability

Stability of reference (meaning, denotation)
We want readers of RDF to be able to understand what writers of RDF write - even if an interval of time (possibly years) passes between the point at which the writing happens and the point at which the reading happens. This is why, in addition to ongoing provision of URI documentation, stability of reference is important: the past writer's understanding of the URI-to-referent association needs to be the same as the future reader's in order for communication to be successful.

Since the association of URI to referent is made via documentation, that means that successive editions of the documentation must written so as to preserve over time the implied association of the URI with its one particular fixed referent.

This does not mean that URI documentation can never change, but it does imply that if it does change (and is not marked "under construction" somehow), then it must not change in a way that affects writers' and readers' understandings of the association.

Stability of documentation
While the documentation may change over time, for example through correction of mistakes of growth of a bibliography, it may not change arbitrarily if stability of reference is to be supported. Thus the changing documentation must have a partially stable meaning in regard to specifying the referent of the URI.

Stability of the referent
It is possible to have a shared understanding of a URI's referent as being a particular thing that changes, without necessarily agreeing on all of the referent's properties over time.

For example, a research laboratory in the sense of a thing in the world may have enough 'rigid properties' (unchanging over time) that time-separated writer and reader can agree that the URI refers to the same laboratory, even though some of its properties, such as current activities, publications list, and personnel, may change over time.

See also Document variability.