Which document captures important data definitions and relationships in a project context?

The correct answer is the Data Dictionary, which plays a significant role in outlining important data definitions and the relationships among various data elements within a project context. A Data Dictionary serves as a comprehensive reference that specifies data types, formats, permissible values, constraints, and relationships between different data items. This structured documentation is crucial for ensuring a shared understanding of data across all stakeholders involved in the project, thus aiding in data integrity, consistency, and effective communication.

In contrast, while a Glossary provides definitions of terms and jargon used within a specific domain or project, it does not delve into the specifics of data relationships or formats in the same depth as a Data Dictionary. A Data Flow Diagram visualizes how data flows within a system but doesn't provide the detailed definitions and contexts that a Data Dictionary does. Business Rules Analysis involves identifying and documenting the rules that govern business operations, which includes other aspects beyond just data definitions. While useful, it does not capture the complete and structured overview of data as a Data Dictionary does.