Posted by kenhoward on November 24, 2008
When requirements analysts are thorough, those who read and use the requirements can easily get lost in the muck and mire of the details. I have found that diagrams can add much more specificity to requirements than lengthy narratives describing business rules. This diagram depicts a small excerpt from a requirements model of a financial system.
This tiny drawing eliminates the need to write out all of the following business rules, because they are all clearly shown in the model:
- Every account must be associated to one customer.
- An account cannot be associated to more than one customer.
- An account cannot exist if it does not have a corresponding customer.
- A customer must have at least one account.
- A customer may have more than one account.
- An account must be either an individual account or a corporate account.
Some restrict the use of drawings like this for design, others argue that domain models are old school. I have had great success using this approach for describing business rules. The economy of words eliminates ambiguity, is much more thorough, and can be easier for a designer/developer to use when designing a solution.