 In addition to Guarino et al. (1994), computational applications of the notion of sortal can be found recently in upper ontology, a relatively new field in computer sciences. For example, Guizzardi and Wagner (2010) make central use of the notion of sortal in a conceptual framework they call Unified Foundational Ontology (UFO). This framework can be used in the design and evaluation of conceptual modeling languages. In UFO, the focus on sortals is on the identity criteria they provide, which contrasts with Guarino et al. (1994) where the emphasis is put instead on countability and persistence. Besides, UFO makes a distinction, among sortals, between rigid and anti-rigid sortals. An instance of a rigid sortal S will be an instance of S in every possible world in which it exists. Anti-rigid sortals will not comply with this feature. From the authors’ examples and further claims, it is clear that rigid sortals correspond to substance sortals and anti-rigid to phase sortals. Because possible worlds are involved, UFO’s framework seems to be committed to individual essentialism. One will then ask whether UFO’s general goal is achievable, given the critique of such essentialism by philosophers of biology. We should finally note that one can also appeal to a tense logic framework to illuminate the distinction between substance and phase sortals, in contrast with UFO’s modal approach.(See Rybola and Pergl (2016a, 2016b) for further examples of recent applications of the notion of sortal in computational ontology.) 