How to Draw Context Diagram

Introduction to Context Diagrams

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In the course of every project that a business analyst encounters, unknown risks and requirements will inevitably arise. The question is when—will they ascend during requirements discovery (ideal), or afterward the project has been deployed (resulting in managerial consternation and costly fixes)? Context diagrams are instrumental in unearthing unknown requirements during the discovery phase, both by forcing an analyst to think through the context (thus the moniker context diagram) of a project methodically and by enabling stakeholders to do and so likewise. As one site aptly notes, "Context diagrams tin can save a project from some very nasty surprises." [ane] Given the return that an analyst gets on her investment (helping to ensure a project's proper direction), the creation of context diagrams is well worth her time.

What is a context diagram?

A context diagram is a graphic design that clarifies the interfaces and boundaries of the project or process at paw. It not only shows the process or project in its context, it also shows the project's interactions with other systems and users. According to Wikipedia, a context diagram is "is the highest level view of a system . . . showing a . . . system as a whole and its inputs and outputs from/to external factors."[2] Further, a context diagram "shows the interactions between a system and other actors with which the arrangement is designed to interface. Organisation context diagrams can be helpful in understanding the context which the organisation volition be function of."[3]

Hither is an example of a context diagram:

A context diagram will fall into one of two categories of rigor:

• The get-go lacks whatever formal structure; an object is but placed in its context, showing its interaction with external entities from a high level. This type of context diagram is normally produced by those who take non had formal training in producing context diagrams, merely who, for a presentation or marketing purposes, desire to prove an object or arrangement in its context. This may also be used in informal settings fifty-fifty past context diagram experts.

• The second type is a scrap more than rigid, cartoon from the same rules, syntax, and symbols established for information menses diagrams. In this example, the context diagram is a subset of a data catamenia diagram with the context diagrams being the simplest form of information flow diagrams.

A projection can take/use multiple context diagrams – for singled-out processes - which can exist revised as more information is discovered or requirements change. Context diagrams are normally included in requirements documents.

Why is a context diagram beneficial?

Context diagrams are instrumental in advancing the thinking process and triggering memory recall of subject affair expects who create and study them. (To that finish, a project may have multiple revised context diagrams that are versioned and archived, or they may be for brainstorming only and never brand it off the white board.) A context diagram will also reveal omissions and errors in a business plan or business organization requirements so that whatever necessary corrections can exist brought to light and addressed before a project is deployed. Kossiakoff wrote, "The objective of a organization 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."[4] The goal is to get feedback from a project's stakeholders and identify whatever missing pieces while the projection is still in the discovery stage. In addition, a context diagram may serve to unambiguously and rapidly define a project'due south scope. It facilitates the discovery and/or confirmation of high-level events that trigger the procedure, including external entities that collaborate with project or process, inputs to and outputs from the projection or process, and initial sub-process requirements.

What are events? When it is mentioned that a context diagram facilitates the discovery of high-level events, that simply means that a context diagram helps its creator and viewers discover all of the occurrences or happenings to which our organization must respond. According to Yourdon, an result may be flow-oriented, significant it is related to a data menses (i.e., customer credit information enters the system so the credit study is updated); temporal, meaning it occurs at a anticipated point in time (i.e., fourth dimension sheets process at 3:00 p.m. CST), or a control upshot, meaning it is an expected event that happens at a particular signal in fourth dimension, but the time is not planned or known ahead of time (i.e., deliveries make it from overseas).[five]

What are the parts of a context diagram?

Context diagrams are made up of simple parts: boxes and lines. According to Wikipedia, "Context diagrams tin be developed with the use of two types of building blocks: labeled boxes, ane in the centre representing the system and around it multiple boxes for each external player, and relationship, labeled lines between the entities and organization".[vi] The two about mutual ways of displaying these are the Gane-Sarson and Yourdon-De Marco symbol sets.[7] (A bit more information about those is available here.) Visio volition adapt either symbol set.

The master parts of a context diagram are:

• The procedure , represented every bit a rounded rectangle, which shows a given process or action at its highest level. A process must react in a preplanned way, and indicates where data is transformed, stored, or distributed. (The top portion of the rectangle is often reserved for the process number.) Examples of how this may expect are beneath.

  

• The external entity may be an actor (person or thing) that either triggers the process or receives output from the process. An external entity may also exist either a information source and/or destination. External entities are represented as rectangular boxes. A few examples are below.

  

• Data flows , represented equally arrows, are the connectors betwixt the main process and the various external entities and prove data flow among them. Again, an case is below.

An instance of these parts displayed together every bit a context diagram is below:

What does a context diagram not include?

Since a context diagram is somewhat loftier-level and focused on the context of the process at hand, information technology does not include any information that is non directly related to that procedure'due south straightforward system. This means that data sources, external communications, culling scenarios, or anything non part of the principal role or system you are diagramming does not need to be included. While these may exist included in a traditional flowchart, they are extraneous to a context diagram. Additionally, a context diagram will never bear witness work flows or actors who initiate data flows (but it will testify the direction of the flow). Context diagrams are not the same as use case diagrams; they do not show the entire process with actors, etc. They only testify the procedure at hand in its context. How do y'all create a context diagram? Y'all can create a context diagram by following eight straightforward steps. Because of the fluid and transformative nature of most context diagrams, a whiteboard may be the best tool to begin their cosmos. Once the diagram is more concrete, it may become an artifact using Visio or some other tool which supports context diagrams:

Context Diagram pitfalls to avoid Examine your context diagram to be sure that none of the following were inadvertently included: Internal actors who initiate data flows or processes (as mentioned above, these have no place in a context diagram) "Black holes," meaning many inputs into the process are depicted simply no outputs. Or the antipodal, "miracles," many outputs come out of the process, merely nothing goes in "Isolated entities," meaning external entities are shown just not linked Entity-to-entity data flows with no process in betwixt

How practise you create a context diagram?

You tin can create a context diagram by following viii straightforward steps. Because of the fluid and transformative nature of almost context diagrams, a whiteboard may be the all-time tool to begin their creation. Once the diagram is more physical, it may become an artifact using Visio or another tool which supports context diagrams:

1: Using a white board or other flexible writing tool, draw a context diagram for the highest level process at paw (known every bit level 0). One time this is completed, that loftier-level process may be farther decomposed into sub-processes. If the sub-processes are fairly contained of each other, they may each exist made into a separate context diagrams (not on level 0) with their own external entities and data flows. If they are sufficiently complex, each of these sub-processes may exist decomposed into farther sub-processes. This technique is topic for a later commodity on data menstruation diagrams.

2: For each distinct high-level process (or organization, functional area being studied) draw the process that acts upon the input. Identify the process in the center of your white board. Label each procedure with a unique numeric identifier (instance: i.0, 2.0) that will enable easy reference and revision in your requirements. Use a verb-substantive construction to characterization the process. An example would be "Take orders." (Ignore the inner workings of the process for this and future steps.)

iii: Next, you volition identify and certificate all external entities that are sources of data to the process you lot just listed. List all the external entities yous tin can think of on the margin of the document. Use nouns to indicate who these entities are. (Examples would be vendors and consumers.) Identify the first source onto the diagram, and cheque it off your list. (Y'all will methodically add the other sources later on.)

4: Next, capture the interactions between this showtime listed source and the procedure. Determine what input(due south) the source provides into the process. Draw the arrow (relationship) and label information technology appropriately. Determine what output the process returns to the source (if any), and depict it accordingly.

v: At present document the additional sources you've already listed and their data flows . Determine for each of the remaining sources if it does something unlike from the source(s) already placed on your diagram. If a source initiates the aforementioned input into the process as a previous source, group them. Otherwise, place it into its own box and depict the data period. Repeat until all sources are off your list.

six: Place and certificate boosted external entities and don't forget about entities which need data from the procedure existence studied. Utilise nouns to signal who these entities are (Example: "Credit Bureau"). Depict their inputs and outputs. Don't worry if you don't know all of these. Capture whatever you can and motion on to the next footstep.

seven: Place and document loftier-level events . For each context diagram, begin these by asking, "How could a source collaborate with this process?" Certificate these events on the margin of your context diagram. Loftier-level events volition be used as inputs.

8: Capture additional requirements . If you happen to discover a requirement during the creation of a context diagram, be sure to annotation it either in your requirements document (be sure to note its source as the context diagram) or in a separate requirements repository designed specifically for requirements unearthed from the creation of context diagrams.

If you lot are not already including context diagrams as a routine part of your requirements discovery and analysis, you are missing a cardinal tool in your armory for ensuring a projection'due south success. Context diagrams are powerful tools for eliciting facts virtually a process are system. However, to exist effective, they must be created for their intended purpose, include their ain inherent characteristics, and not be confused with use cases, flowcharts, or like tools. When used as intended, context diagrams are a strong tool for ensuring a project's success.

More than on Context Diagrams:

• Article: Putting Systems Assay "Into Context" using the Context Diagram
• Question: What is a Context Diagram and what are the benefits of creating ane?
• Forum Mail service: Context Diagram: Depository financial institution ATM Example

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Author: Morgan Masters is Concern Analyst and Staff Writer at ModernAnalyst.com , the premier customs and resource portal for business organization analysts. Business concern assay resources such equally manufactures, blogs, templates, forums, books, along with a thriving business analyst customs can be plant at http://www.ModernAnalyst.com

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[1] http://www.pqsw.com/hjsasp/gn02.cfm?SI=43479230767&ID=921210469186

[ii]  http://en.wikipedia.org/wiki/System_context_diagram

[3] Ibid.

[4] Ibid.

[v] http://yourdon.com/strucanalysis/wiki/index.php?championship=Chapter_18#The_Context_Diagram

[half-dozen] http://en.wikipedia.org/wiki/System_context_diagram

[vii] http://www.pqsw.com/hjsasp/gn02.cfm?SI=43479230767&ID=921210469186

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How to Draw Context Diagram

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