Business Process Modeling, BPM, and Data Modeling, DM, are two disciplines key to designing a robust Business Application. BPM outlines process, procedures and business logic used to run the business. DM organizes the data stored to manage and measure business performance. Unfortunately, these two activities are loosely connected during requirements analysis.
Logically, a Business Application is a collection of both process and data that have a close affinity to each other. The affinity between process and data is determined by what actions the process takes on the data. For example, data created by a process has a close affinity while data that is read only does not.
A modified version of IDEF0 is an excellent way to understand the relationship between process and data. IDEF0 notation shows that in addition to process logic, a process has inputs, outputs, controls and mechanims. In the world of data processing, the inputs, controls, and outputs represent all the data needed for a process. The mechanism represents the system or technology used to perform the process. 
Inputs to a process can be data from an upstream system or maybe an application that is keyed into a business application to open an account. The controls are read only data such as rules or reference data required to govern a process. Output is the data that is captured about the business process. What key is that the output is data created by the process. Knowing where data is created is key to establishing data quality for you business.
Using this simply notation will help you tie your data to the key processes. It will ensure that all the data needed is available to the business process. In addition, understanding the affinity between the process and data will help you properly define and manage the scope of the buiness application you’re designing.