Where used: Mapping Model


hasCoimage / isCoimageOf

Mapping hasCoimage Object Type

Object Type isCoimageOf Mapping


The co-image of a mapping is the subset of the domain for which the
mapping returns something.  For example, the Pet-Of mapping from humans
to animals will have an subtype of humans that own pets at any given
time, namely Pet-Owner, which is the co-image.  Whereas the domain gives
the inputs that possibly have results, the co-image gives the inputs
that actually have results.  The co-image may be the same as the domain.

The image of a mapping is the subset of the range which the mapping
actually returns as output.  For example, the Pet-Of mapping from humans
to animals will have an subtype of animals that are pets at any given
time, namely Pet, which is the image.  Whereas the range gives the
possible results of the mappings, the image gives the actual results. If
the image is the same as the range, the mapping is said to be "onto" or
"surjective"; otherwise it is called "into".

Since mappings always return sets, to accommodate multiple-values and
no-values, it is more exact to say that the co-image is the subset of
the domain which maps to a non-empty set.

The three techniques for modelling images also apply to co-images (see
hasImage/isImageOf), substituting Pet-Owner for Pet, and domain for
range.

See Place Relation for discussion of the similarities and differences
between images and role types.

See the summary with example at Place Relation.