Which of the following is NOT a tool used in structured analysis?

In structured analysis, various tools are utilized to depict and analyze the system requirements and processes. Context diagrams, Data Flow Diagrams (DFDs), and Data Dictionaries are fundamental components of this methodology. A context diagram provides a high-level view of the system by illustrating how it interacts with external entities, which helps to establish the system's boundaries. Data Flow Diagrams represent the flow of data within the system, detailing processes and data stores, essential for understanding how information moves and transforms. The Data Dictionary is a repository that holds metadata about the data involved in the system, including definitions and formats, serving as a reference point for the overall data architecture.

In contrast, use-case models belong to object-oriented analysis rather than structured analysis. They focus on capturing functional requirements from the user's perspective and emphasize system interactions, making them better suited to methodologies that prioritize use cases, such as Unified Modeling Language (UML). Thus, use-case models do not align with the core tools of structured analysis, which is why they do not fit in this context.