For the practical application of the pattern, one can look at the term assay from the Ontology of Biomedical Investigations (OBI) as shown in Figure , which is particularly suitable for illustrative purposes. This example shows that the textual definition first references planned process, as it is formally defined as the superclass of assay, and then provides the necessary and sufficient criteria for why assay must be understood as a special kind of planned process in the context of OBI. The Differentia phrase of this definition makes use of words that refer to specific classes which are also defined in OBI, as can be seen by the asserted axioms. The omission of "An assay is is a planned process . . . " is because the annotation is recognizable by the human reader as the textual definition of the term assay, but more importantly, it does not need to be rewritten if the developers decide to change the label assay to a possibly more intelligible one.