to business processes. Other types of modeling done by organizations for non-process purposes are out of scope for BPMN. Examples of modeling excluded from BPMN are: Organizational structures Functional breakdowns Data models In addition, while BPMN shows the flow of data (messages), and the association of data artifacts to activities, it is not a data flow diagram. Elements BPMN models are expressed by simple diagrams constructed from a limited set of graphical elements. For both business users and developers, they simplify understanding of business activities' flow and process. BPMN's four basic element categories are: Flow objects Events, activities, gateways Connecting objects Sequence flow, message flow, association Swim lanes Pool, lane, Dark Pool Artifacts Data object, group, annotation These four categories enable creation of simple business process diagrams (BPDs). BPDs also permit making new types of flow object or artifact, to make the diagram more understandable. Flow objects and connecting objects Flow objects are the main describing elements within BPMN, and consist of three core elements: events, activities, and gateways. Event An Event is represented with a circle and denotes something that happens (compared with an activity, which is something that is done). Icons within the circle denote the type of event (e.g., an envelope representing a message, or a clock representing time). Events are also classified as Catching (for example, if catching an incoming message starts a process) or Throwing (such as throwing a completion message when a process ends). Start event Acts as a process trigger; indicated by a single narrow border, and can only be Catch, so is shown with an open (outline) icon. Intermediate event Represents something that happens between the start and end events; is indicated by a double border, and can Throw or Catch (using solid or open icons as appropriate). For example, a task could flow to an event that throws a message across to another pool, where a subsequent event waits to catch the response before continuing. End event 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. Activity 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. Task A task represents a single unit of work that is not