b is a continuant fiat boundary = Def. b is an immaterial entity that is of zero, one or two dimensions and does not include a spatial region as part. (axiom label in BFO2 Reference: [029-001]) [ http://purl.obolibrary.org/obo/bfo/axiom/029-001 ]

#### Term information

**editor note**

BFO 2 Reference: a continuant fiat boundary is a boundary of some material entity (for example: the plane separating the Northern and Southern hemispheres; the North Pole), or it is a boundary of some immaterial entity (for example of some portion of airspace). Three basic kinds of continuant fiat boundary can be distinguished (together with various combination kinds [29

Continuant fiat boundary doesn't have a closure axiom because the subclasses don't necessarily exhaust all possibilites. An example would be the mereological sum of two-dimensional continuant fiat boundary and a one dimensional continuant fiat boundary that doesn't overlap it. The situation is analogous to temporal and spatial regions.

BFO 2 Reference: In BFO 1.1 the assumption was made that the external surface of a material entity such as a cell could be treated as if it were a boundary in the mathematical sense. The new document propounds the view that when we talk about external surfaces of material objects in this way then we are talking about something fiat. To be dealt with in a future version: fiat boundaries at different levels of granularity.More generally, the focus in discussion of boundaries in BFO 2.0 is now on fiat boundaries, which means: boundaries for which there is no assumption that they coincide with physical discontinuities. The ontology of boundaries becomes more closely allied with the ontology of regions.

**has associated axiom(fol)**

(iff (ContinuantFiatBoundary a) (and (ImmaterialEntity a) (exists (b) (and (or (ZeroDimensionalSpatialRegion b) (OneDimensionalSpatialRegion b) (TwoDimensionalSpatialRegion b)) (forall (t) (locatedInAt a b t)))) (not (exists (c t) (and (SpatialRegion c) (continuantPartOfAt c a t)))))) // axiom label in BFO2 CLIF: [029-001]

**has associated axiom(nl)**

Every continuant fiat boundary is located at some spatial region at every time at which it exists