What are object symbols for?

Objects have characteristics and relationships with other items. Object symbols are graphical representations of objects in models. Models are easy to read if a given factor, such as an executable activity, is always represented by the same object symbol. 

For example, an executable activity is always represented by the Function object type. This is a function with the Human task object symbol:

Activity

Executable activity in a model of the EPC type with the object symbol Function:

Function object symbol