The paper presents a similarity-based retrieval framework for a software repository that aids the process of maintaining, understanding, and migrating legacy software systems [12]. Designing a software repository involves three issues: (1) information content; (2) information representation; and (3) strategies for accessing repository artifacts. Assuming the architecture presented in [12] we extend the retrieval system to support imprecise queries, iterative browsing, and diverse users. Because of repository size, complexity of queries and relations among artifacts, we take a performance approach to support a scalable implementation. We propose a retrieval system that uses numeric [31] and semantically rich context-based similarity [19]. Efficient iterative browsing is based on an incremental query evaluation algorithm from database management systems [20]. Explicitly defined context supports various retrieval strategies and diverse user models.