As many of you who are familiar with RML know, the models are organized into 3 categories: people, systems and data.
People models are models that relate to who is using the system and how they need to use the system to perform their jobs. The top level model is the organizational chart which allows you to be confident that you have covered all the possible users. Additional models include use cases and process flows.
System models relate to the system and its logical structure. The top level model is a system context diagram that shows how the logical systems (from a business user’s perspective) relate to each other. The system context diagram ensures that a complete list of systems is maintained and can be analyzed in an orderly and complete fashion. Additional models include the Display Action Response (DAR), process flows, interface model and state diagrams.
Finally the data models describe the data within the system. The top level data model is the business data diagram (BDD) which shows all the data in the system and how the data relates to other data. Other data models include report tables, data dictionaries and data flow diagrams.
We have found that business users have trouble comprehending the complexities behind BDDs which describe the 1 to many relationship of data elements. We have often found ourselves using a diagram that we call the Business Data Instance Diagram. It is similar to a Business Data Diagram in that it shows the relationship of data elements to each other. However rather than using a single line to show the relationship, we actually show the multiple data elements.
You can include 0 or 1 to many notation using a 0 or 1 and then … below the last box in a series to convey that there are multiple. For our purposes in this diagram it was overkill and we felt that this diagram shows what we intended it to show. As you can see this diagram it can become messy very quickly if you try to show all the linkages. The BDID should be used in conjunction with a BDD to help to clarify particular tricky relationships.