System context diagram

System context diagram
Example of a System context diagram.[1]

A System Context Diagram (SCD) in software engineering and systems engineering is a diagram that represents the actors outside a system that could interact with that system.[2] This diagram is the highest level view of a system. It is similar to a Block diagram. SCDs show a system, often software-based, as a whole and its inputs and outputs from/to external factors.



System Context Diagrams are diagrams used in systems design to represent the more important external factors that interact with the system at hand. This type of diagram according to Kossiakoff (2003) usually "pictures the system at the center, with no details of its interior structure, surrounded by all its interacting systems, environment and activities. The objective of a system context diagram is to focus attention on external factors and events that should be considered in developing a complete set of system requirements and constraints".[2]

System context diagrams are related to UML, and show the interactions between a system and other actors with which the system is designed to interface. System context diagrams can be helpful in understanding the context which the system will be part of.

Context diagrams are used early in a project to get agreement on the scope under investigation. Context diagrams are typically included in a requirements document. These diagrams must be read by all project stakeholders and thus should be written in plain language, so the stakeholders can understand items within the document.

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 ovals, stick figures, pictures, 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[3] (Examples: [4]), which add clarity to the level of involvement of the entity with regards to the system. These categories include:

  • Active: Dynamic external entities which frequently initiate events 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").


The best System Context Diagrams are used to display how system inter operates at a very high level or how systems operate and interact logically. The system context diagram is a necessary tool in developing a baseline interaction between systems and actors; actors and system or systems and systems. Alternatives of the system context diagram are:

Example of an Architecture Interconnect Diagram.[5]
  • Use case diagram: One of the Unified Modeling Language diagrams. They also represent the scope of the project at a similar level of abstraction. - Use Cases however tend to focus more on the goals of 'actors' who interact with the system, and do not specify any solution. Use Case diagrams represent a set of Use Cases, which are textual descriptions of how an actor achieves the goal of a use case. for Example : Customer Places Order.
  • IDEF0 Top Level Context Diagram: The IDEF0 process starts with the identification of the prime function to be decomposed. This function is identified on a “Top Level Context Diagram” that defines the scope of the particular IDEF0 analysis.
  • Enterprise data model: this type of data model according to Simsion (2005) can contain up to 50 to 200 entity classes, which results from specific "high level of generalization in data modeling".[6]
  • Architecture Interconnect Diagram: The figure gives an example of an Architecture Interconnect Diagram: A representation of the Albuquerque regional ITS architecture interconnects for the Albuquerque Police Department that was generated using the Turbo Architecture tool is shown in the figure. Each block represents an ITS inventory element, including the name of the stakeholder in the top shaded portion. The interconnect lines between elements are solid or dashed, indicating existing or planned connections.[5]
  • Problem Diagrams (Problem Frames): In addition to the kinds of things shown on a context diagram, a problem diagram shows requirements and requirements references.

Diagrams like these work well as long as a limited number of interconnects will be shown. Where twenty or more interconnects must be displayed, the diagrams become quite complex and can be difficult to read. [5]

See also


  1. ^ NDE Project Management (NPOESS) Data Exploitation web site. 2008.
  2. ^ a b Alexander Kossiakoff, William N. Sweet (2003). Systems Engineering: Principles and Practices p. 413.
  3. ^
  4. ^
  5. ^ a b c US Department of Transportation, Office of Operations (2006)Regional ITS Architecture Guidance Document. July 2006
  6. ^ Graeme C. Simsion, Graham C. Witt (2005). Data Modeling Essentials. p. 512.

Wikimedia Foundation. 2010.

Игры ⚽ Нужно решить контрольную?

Look at other dictionaries:

  • context diagram — /ˈkɒntɛkst daɪəgræm/ (say kontekst duyuhgram) noun a diagram that provides a model of a whole system by representing it as one process with inputs or outputs from external entities …  

  • Diagram — Further information: Chart Sample flowchart representing the decision process to add a new article to Wikipedia. A diagram is a two dimensional geometric symbolic representation of information according to some visualization technique. Sometimes …   Wikipedia

  • Data flow diagram — example.[1] A data flow diagram (DFD) is a graphical representation of the flow of data through an information system, modelling its process aspects. Often they are a preliminary step used to create an overview of the system which can later be… …   Wikipedia

  • Cluster diagram — A Cluster diagram or clustering diagram is a general type of diagram, which represents some kind of cluster. A cluster in general is a group or bunch of several discrete items that are close to each other. [1] The cluster diagram figures a… …   Wikipedia

  • Functional flow block diagram — The Functional Flow Block Diagram (FFBD) is a multi tier, time sequenced, step by step flow diagram of the system’s functional flow. [The first version of this article is completely based on the [ org/headquarters… …   Wikipedia

  • Dynkin diagram — See also: Coxeter–Dynkin diagram Finite Dynkin diagrams Affine (extended) Dynkin diagrams …   Wikipedia

  • Solar System — This article is about the Sun and its planetary system. For other systems, see planetary system and star system. For a list of physical and orbital statistics for the Solar System s largest bodies, see List of gravitationally rounded objects of… …   Wikipedia

  • Root system — This article discusses root systems in mathematics. For root systems of plants, see root. Lie groups …   Wikipedia

  • Use case diagram — A use case diagram is a type of behavioral diagram defined by the Unified Modeling Language (UML) and created from a Use case analysis. Its purpose is to present a graphical overview of the functionality provided by a system in terms of actors,… …   Wikipedia

  • Single context recording — was developed in the 1970 s by the Museum of London amongst others (notably at Winchester and York, where the system was first used) and has become the defacto recording system in many parts of the world and is especially suited to the… …   Wikipedia

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”