Acknowledging the basic concepts


Context

The first diagram of a model, the one corresponding to the most global view of the system or organization being represented, is called by default the context. The Context is the process level 0.


Process

A process is used to represent a function to be carried out by the system. Processes are provided with input flows to generate output flows.


External entity

An external entity represents a system or organization which interacts with the described system. Modelers do not have to further detail the external entity in the project since its internal structure and organization is of no relevance to the current project. External entities can be persons, institutions or simple objects that are the source or destination of flows.


Flow

A flow represents a movement or the circulation of information, matter, energy etc. from one point to another. Generally a flow has a direction that is indicated by the presence of an arrowhead at either or both extremities. The exchanges they represent may be discrete or continuous.


Store

A store is used to store or record whatever circulates through flows within a diagram.


Resource

Processes are performed by human or technical resources. Human resources are, for instance, organizational units, and technical resources are machines, computers, printers etc. Resources can be shared among processes or assigned exclusively.


Qualifiers

Qualifiers are icons or pictures used to illustrate the nature of external entities, flows, processes and stores.