<Dd> Represents the result of a process; indicated by a single thick or bold border, and can only Throw, so is shown with a solid icon . </Dd> <Dl> <Dt> Activity </Dt> <Dd> An activity is represented with a rounded - corner rectangle and describes the kind of work which must be done . An activity is a generic term for work that a company performs . It can be atomic or compound . <Dl> <Dt> Task </Dt> <Dd> A task represents a single unit of work that is not or cannot be broken down to a further level of business process detail . It is referred to as an atomic activity . A task is the lowest level activity illustrated on a process diagram . A set of tasks may represent a high - level procedure . </Dd> <Dt> Sub-process </Dt> <Dd> Used to hide or reveal additional levels of business process detail . When collapsed, a sub-process is indicated by a plus sign against the bottom line of the rectangle; when expanded, the rounded rectangle expands to show all flow objects, connecting objects, and artifacts . A sub-process is referred to as a compound activity . </Dd> <Dd> Has its own self - contained start and end events; sequence flows from the parent process must not cross the boundary . </Dd> <Dt> Transaction </Dt> <Dd> A form of sub-process in which all contained activities must be treated as a whole; i.e., they must all be completed to meet an objective, and if any one of them fails, they must all be compensated (undone). Transactions are differentiated from expanded sub-processes by being surrounded by a double border . </Dd> <Dt> Call Activity </Dt> <Dd> A point in the process where a global process or a global Task is reused . A call activity is differentiated from other activity types by a bolded border around the activity area . </Dd> </Dl> </Dd> </Dl> <Dd> An activity is represented with a rounded - corner rectangle and describes the kind of work which must be done . An activity is a generic term for work that a company performs . It can be atomic or compound . <Dl> <Dt> Task </Dt> <Dd> A task represents a single unit of work that is not or cannot be broken down to a further level of business process detail . It is referred to as an atomic activity . A task is the lowest level activity illustrated on a process diagram . A set of tasks may represent a high - level procedure . </Dd> <Dt> Sub-process </Dt> <Dd> Used to hide or reveal additional levels of business process detail . When collapsed, a sub-process is indicated by a plus sign against the bottom line of the rectangle; when expanded, the rounded rectangle expands to show all flow objects, connecting objects, and artifacts . A sub-process is referred to as a compound activity . </Dd> <Dd> Has its own self - contained start and end events; sequence flows from the parent process must not cross the boundary . </Dd> <Dt> Transaction </Dt> <Dd> A form of sub-process in which all contained activities must be treated as a whole; i.e., they must all be completed to meet an objective, and if any one of them fails, they must all be compensated (undone). Transactions are differentiated from expanded sub-processes by being surrounded by a double border . </Dd> <Dt> Call Activity </Dt> <Dd> A point in the process where a global process or a global Task is reused . A call activity is differentiated from other activity types by a bolded border around the activity area . </Dd> </Dl> </Dd> <Dl> <Dt> Task </Dt> <Dd> A task represents a single unit of work that is not or cannot be broken down to a further level of business process detail . It is referred to as an atomic activity . A task is the lowest level activity illustrated on a process diagram . A set of tasks may represent a high - level procedure . </Dd> <Dt> Sub-process </Dt> <Dd> Used to hide or reveal additional levels of business process detail . When collapsed, a sub-process is indicated by a plus sign against the bottom line of the rectangle; when expanded, the rounded rectangle expands to show all flow objects, connecting objects, and artifacts . A sub-process is referred to as a compound activity . </Dd> <Dd> Has its own self - contained start and end events; sequence flows from the parent process must not cross the boundary . </Dd> <Dt> Transaction </Dt> <Dd> A form of sub-process in which all contained activities must be treated as a whole; i.e., they must all be completed to meet an objective, and if any one of them fails, they must all be compensated (undone). Transactions are differentiated from expanded sub-processes by being surrounded by a double border . </Dd> <Dt> Call Activity </Dt> <Dd> A point in the process where a global process or a global Task is reused . A call activity is differentiated from other activity types by a bolded border around the activity area . </Dd> </Dl>

What do rectangles with rounded corners in the bpmn model denote