Editing System context diagram (section)

== Building blocks ==
Context diagrams can be developed with the use of two types of building blocks:
* ''Entities (Actors)'': labeled boxes; one in the center representing the system, and around it multiple boxes for each external actor
* ''Relationships'': labeled lines between the entities and system

For example, "customer places order." Context diagrams can also use many different drawing types to represent external entities. They can use [[Oval (geometry)|oval]]s, [[stick figure]]s, [[picture]]s, [[clip art]] or any other representation to convey meaning. Decision trees and data storage are represented in system flow diagrams.

A context diagram can also list the classifications of the external entities as one of a set of simple categories<ref>Suzanne Robertson, James C. Robertson (2006) ''Mastering the Requirements Process''. Pearson Education, 17 mrt. 2006</ref> (Examples:<ref>[http://www.city.ac.uk/__data/assets/pdf_file/0006/81429/RESCUE_i_SD_tutorial.pdf System Goal Modelling using the i*: Approach in RESCUE] Centre HCI Design, 27 February 2003</ref>), which add clarity to the level of involvement of the entity with regards to the system. These categories include:
* ''Active'': Dynamic to achieve some goal or purpose (Examples: "Article readers" or "customers").
* ''Passive'': Static external entities which infrequently interact with the system (Examples: "Article editors" or "database administrator").
* ''Cooperative'': Predictable external entities which are used by the system to bring about some desired outcome (Examples: "Internet service providers" or "shipping companies").
* ''Autonomous (Independent)'': External entities which are separated from the system, but affect the system indirectly, by means of imposed constraints or similar influences (Examples: "regulatory committees" or "standards groups").