  In this paper we argue that representing entity properties by tuple
attributes, as evangelized in most set-oriented data models, is a controversial
method conflicting with the principle of tuple immutability. As a principled
solution to this problem of tuple immutability on one hand and the need to
modify tuple attributes on the other hand, we propose to use mathematical
functions for representing entity properties. In this approach, immutable
tuples are intended for representing the existence of entities while mutable
functions (mappings between sets) are used for representing entity properties.
In this model, called the concept-oriented model (COM), functions are made
first-class elements along with sets, and both functions and sets are used to
represent and process data in a simpler and more natural way in comparison to
purely set-oriented models.
