Often, when business analysts start projects, they are required to define the scope of work that will be involved in implementing a new system. One way to do this, is to draw up a context diagram that graphically illustrates the full scope of the system.
What is a context diagram? This is a simple but powerful tool that clearly shows the system under consideration and the various external entities that interact with it. A context diagram shows at a very high level:
- The system boundaries
- The external enties – these could be people or other systems
- The information that flows between the system and these external entities
External entities may include various stakeholders and systems that have direct interactions with the system under consideration. It is not to be confused with the use case diagram which is more detailed and includes detail down to the process level.
Why is it important? This very useful tool is often overlooked by business analysts as they believe it does not add much value. The team at Analyze, however, believe that it is a critical step in the initiation phase of a project. The context diagram is a tool that will be a central reference point for scope.
How to draw one up? The key is to ensure that the context diagram depicts the project scope simply but accurately.
Here are our top tips on drawing the context diagram:
- Start by drawing the main system under consideration in the middle of the page.
- List all external entities around the system. NB. Only list those external entities that have direct contact with the system.
- Taking each external entity, describe the relationship it has with the system. This relationship includes – what kind of information the entity will require from the system and what their main interactions with the system will be.
- Represent this relationship with a line between the entity and the system. Use an arrow on each line to indicate the direction of the information flow, either towards the external entity or towards the system. Describe the information that moves between the entity and the system. Information may only flow in one direction.
- Follow step 3 and 4 again for the opposite relationship i.e. relationship between the system and the external entity.
An example? Take for example a new e-commerce website being developed for a retail chain. The main system under consideration will be the e-commerce website. The various external entities may include customers, staff, management and payment system.
- Customers can register on the system, view different goods for sale, place orders, make payments, track orders etc.
- Staff can update inventory (prices and goods) on the system, view customer orders, track customer orders, process orders placed by customers etc.
- Management can access reports on goods sold, user statistics, stock levels etc.
- The payment system can process payments, send notification of successful/failed payments etc.
Ecommerce Website Example
You can see from the example above, that the context diagram is really valuable in defining the scope of a project at a high level. This ensures that all project stakeholders are on the same page from the get go.
Having problems defining scope? Contact us today to find out how we can help you in defining the scope of your project.