The Property data structure consists of three elements: Items of Property, Units and Buildings.

In most cases only Items of Property and Units are needed. These would reflect for example an apartment building (Item of Property) and each apartment inside that building (Unit).

In some cases a third layer is needed. For example, if we think of a high rise, that is separated in a commercial area inside the lower floors and a residential area in the upper floors.

In this case we might want to separate the commercial and the residential area in two different entities for example for accounting purposes. It is very well possible, that we have different security systems or service providers for the two different areas. So we don’t want to burden the accounting for the residential areas with the cost for security of the commercial area and vice versa.

However, both areas are still in the same building.

In that case we may want to have two Items of Property, each with a number of units (commercial or residential respectively) and an “envelope” data structure, that links the two together. That is the data item of an Building in PMX Property Management.