Engagements typically involve improvements to a process or software system or both. Modeling the process, actors, workflow, domain objects and documenting the business events, and business rules is a very effective way to validate strategy or objectives, identify gaps and also be useful input to scoping and implementation.
Below are the links to an example of a set of artifacts used to confirm a business process, workflow states, business domain and future state user interface. Once the models are confirmed with stakeholders: problems to be solved are agreed to; risks to be mitigated are widely known; business cases are done; and mockups are created to describe the UI in a purchased or custom built solution. The same artifacts can be re-used to scope the solution and typically help to shorten the development cycles since there is a shared understanding of the risks mitigated and problems to be solved.