Abstract
The increasing complexity of systems within Model-Based Systems Engineering (MBSE) environments has made structured and reliable use case modeling critically important. Existing approaches to SysML Use Case Diagram modeling and verification remain fragmented, addressing generation, validation, or reuse in isolation. This paper presents UCDForge, a unified intelligent framework combining a rule-based verification engine, an LLM-assisted extraction pipeline, and a hybrid Case-Based Reasoning mechanism integrating pyCBR and myCBR for SysML Use Case Diagram modeling and verification. The verification module enforces structural, spatial, linguistic, and relationship rules against XML diagrams of the open-source toolkit TTool, while the generation module transforms natural language descriptions into standards-compliant diagrams through LLM extraction, hybrid CBR retrieval, and human-in-the-loop refinement. As an exploratory research contribution, the framework shows promising initial results in both violation detection and relevant case retrieval, suggesting its potential as a reliable and adaptive modeling assistant within MBSE environments.