External Entity Descriptions for the Current Physical Dataflow Model (slide 20)
External Entity Descriptions
In the current physical, External Entities are used to show sources and recipients of data from the business system under investigation. They can represent:
- Other business systems
- Computer systems
At this stage, the operational staff are considered to be part of the processes so they tend not to be shown.
As usual, though, bend the rules if it helps with communication and show any that are sources / recipients of 'important' flows of data, e.g. a manager providing authorisation or a user triggering a process.
The External Entities listed in the table below all come from the top level DFD. It's possible that more will be discovered as the DFD is decomposed into lower levels.
|Accounts||The accounts department. They do all
the invoicing, debt chasing, credit checking and financial reporting.
|Courier||Items are usually delivered to customers
via a courier service. The present service is provided by Alacrity Courier
|Customer||Customers are retail outlets, concessions and mail order firms. Acme Fashion Supplies doesn't sell to individuals.|
|Marketing Department||The marketing department introduce new products and decide on those to be withdrawn. They also do mailshots to customers.|
|Supplier||Acme Fashion Supplies buys products from suppliers. They are delivered by a variety of methods, sometimes courier, sometimes by suppliers' own delivery vans. Their are four major suppliers and a number who supply niche items.|
|Travelling Sales Team||Acme Fashion Supplies have a small travelling sales team. As part of this they bring or phone in orders.|