What is a context diagram? (5)
- also: Context-Level Data-Flow Diagram or Level-0 Data Flow Diagram
- is a graphic design that clarifies the interfaces and boundaries of the project or process at hand
- shows the system under consideration as a single high-level process
- shows the relationship system has with other external entities (systems, organizational groups, external data stores, etc.)
- is a specialized version of Data-Flow Diagram
What is a context diagram used for? (4)
- systems analysis and design
- to capture and communicate the interactions and flow of data between business processes
- will reveal omissions and errors in a business plan or business requirements
- is to get feedback from a project’s stakeholders and identify any missing pieces while the project is still in the discovery stage
A Context Diagram (and a … for that matter) provides no information about the … such as which processes occur in sequence or in parallel.
DFD; timing, sequencing, or synchronization of processes
What are the benefits of context diagrams? (5)
- Shows scope and boundaries of a system at a glance including the other systems that interface with it
- No technical knowledge is assumed or required to understand the diagram
- Easy to draw and amend due to its limited notation
- Easy to expand by adding different levels of DFDs
- Can benefit a wide audience including stakeholders, business analyst, data analysts, developers
In the course of every project that a … encounters, unknown risks and requirements will inevitably arise. The question is when will they arise during … , or after the project has been …? Context diagrams are instrumental in … requirements during the … phase, both by forcing an analyst to think through the … of a project methodically and by enabling stakeholders to do so as well.
business analyst
requirements discovery
deployed
unearthing unknown
discovery
context
What types of high-level events does a context diagram help to identify? (3)
Flow-oriented events, related to a data flow
Temporal events, occurring at a predictable point in time
Control events, related to an expected event that happens at a particular point in time, but the time is not planned or known ahead of time
What are the parts of a context diagram? (5)
name of part: represented how? / showing what?
Processes: represented as rounded rectangles / shows a given process or activity at its highest level
-top portion of the rectangle is often reserved for the process number
External entities: represented as rectangular boxes / actor that either triggers the process or receives output from the process
-entities may be either a data source and/or destination
Data flows: represented as arrows / connectors between the main process and the various external entities
What does a context diagram should never include? (3)
- no information not directly related to that process’s straightforward system
- no data sources, external communications, alternative scenarios, or anything not part of the main function or system you are diagramming
- will never show work flows or actors who initiate data flows
What are common errors a designer may make when creating a context diagram? (5)
- Internal actors who initiate data flows or processes
- “Black holes,” meaning many inputs into the process are depicted but no outputs
- “Miracles,” many outputs come out of the process, but nothing goes in
- “Isolated entities,” meaning external entities are shown but not linked
- Entity-to-entity data flows with no process in between
What are the 8 steps to creating a context diagram?
- Draw highest level process
- Draw process acting upon input in centre and label it depending on level
- Identify and document all external entities in small list in margin, include first external entity in diagram and tick off list
- Draw and label relationships between entity and process
- Include other external entities and their relationships
- Try to find more external entities
- Identify and document high-level events in margins (they are used as inputs)
- Capture additional requirements you discover while creating the diagram
What type of diagram is this?
a Context Diagram
