${?}_{{?}_{{?}_{?}}{?}_{{?}_{?}}{?}_{{?}_{?}}{?}_{{?}_{?}}{?}_{{?}_{?}}{?}_c\text{l}\text{a}\text{s}\text{s}\text{e}\text{s}\text{m}\text{a}\text{n}\text{a}\text{g}\text{e}aunitof\text{w}\text{o}\text{r}\text{k}\text{f}\text{r}\text{o}\text{m}\text{s}\text{t}\text{a}\text{r}\text{t}to\text{f}\text{i}\text{n}\text{i}\text{s}\text{h}\text{.}\text{T}\text{h}\text{e}\text{y}\text{c}\text{a}\text{n}be\text{d}\text{e}\text{s}\text{i}\text{g}\text{n}\text{e}\text{d}to\text{m}\text{a}\text{n}\text{a}\text{g}\text{e}}$

the creation $or$ update $of$ entity objects;

the instantiation $of$ boundary objects $as$ they obtain information from entity objects;

complex communication between sets $of$ objects;

validation $of$ data communicated between objects $or$ between the user and the application.