An activity is performed as part of a process. It can be atomic or non-atomic (compound). BPMN uses three categories of activities: Process, Subprocess, and Task.

BPMN provides the following symbols for activities:

In ARIS, activities are modeled as functions by default:

The function is provided with all attributes that BPMN defines for processes, subprocesses, and tasks. As with events, the BPMN attribute type group is used, which contains additional subgroups for the activity types.

In terms of BPMN, a process describes an activity that is performed within a company or organization. A process is described by a graph with flow objects that represent a set of different activities and control objects. Processes are hierarchically structured and can be defined at all levels of detail. In contrast to a process, a business process in BPMN describes a set of activities that are performed across corporate/organizational boundaries.

In terms of BPMN, a subprocess is a combined activity with a detailed description. A subprocess occurs as an object within a process flow.

Usually, a subprocess is assigned a detailed process. Unlike in BPMN, ARIS does not identify an assigned activity by a plus sign, but by an assignment icon.

Besides identifying an assigned function, BPMN also provides the ability to show the detail process at the next higher process level. This is done by clicking the plus sign.