OOD

Question 1

What is a context diagram? (5)

Answer 1

• 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

Question 2

What is a context diagram used for? (4)

Answer 2

• 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

Question 3

A Context Diagram (and a … for that matter) provides no information about the … such as which processes occur in sequence or in parallel.

Answer 3

DFD; timing, sequencing, or synchronization of processes

Question 4

What are the benefits of context diagrams? (5)

Answer 4

• 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

Question 5

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.

Answer 5

business analyst

requirements discovery

deployed

unearthing unknown

discovery

context

Question 6

What types of high-level events does a context diagram help to identify? (3)

Answer 6

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

Question 7

What are the parts of a context diagram? (5)

name of part: represented how? / showing what?

Answer 7

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

Question 8

What does a context diagram should never include? (3)

Answer 8

• 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

Question 9

What are common errors a designer may make when creating a context diagram? (5)

Answer 9

• 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

Question 10

What are the 8 steps to creating a context diagram?

Answer 10

1. Draw highest level process
2. Draw process acting upon input in centre and label it depending on level
3. Identify and document all external entities in small list in margin, include first external entity in diagram and tick off list
4. Draw and label relationships between entity and process
5. Include other external entities and their relationships
6. Try to find more external entities
7. Identify and document high-level events in margins (they are used as inputs)
8. Capture additional requirements you discover while creating the diagram

Question 11

What type of diagram is this?

Answer 11

a Context Diagram