Explanation
A data flow diagram is a technique that helps to create a high-level overview of a business process by showing the movement and transformation of data between entities and processes. A data flow diagram uses graphical symbols and arrows to represent the sources and destinations of data, the processes that manipulate data, the data stores that store data, and the data flows that transfer data. A data flow diagram can help the BA to understand the current state of the business process, to identify the data requirements and dependencies, and to communicate the data logic and structure to the stakeholders. An entity relationship diagram is a technique that helps to represent the data and information needs of an organization or a solution using graphical or textual symbols and relationships. An entity relationship diagram shows the entities that are relevant to the domain, the attributes that describe the entities, and the relationships that exist between the entities. An entity relationship diagram can help the BA to define and analyze the data requirements, but it does not show the movement and transformation of data between entities and processes. A scope model is a technique that helps to define the boundaries and context of a project or a solution. A scope model shows the elements that are within the scope, the elements that are out of scope, and the interfaces and interactions between the elements.
A scope model can help the BA to clarify the scope and objectives of the project or solution, but it does not show the movement and transformation of data between entities and processes. A process model is a technique that helps to represent the activities and tasks that are performed to achieve a specific goal or outcome. A process model shows the sequence and flow of the activities and tasks, the roles and responsibilities of the performers, the inputs and outputs of each activity or task, and the rules and conditions that govern the process. A process model can help the BA to define and analyze the business process, but it does not show the movement and transformation of data between entities and processes. References: BABOK Guide v3, Chapter
10: Techniques, Section 10.18: Data Flow Diagrams, p. 522-524; Section 10.19: Data Modeling, p. 525-527; Section 10.42: Scope Modeling, p. 554-556; Section 10.43: Process Modeling, p. 557-559.