Latent topic models are statistical structures in which a "latent topic" describes some relationship between parts of the data. Co-maintenance is defined as an observable property of software systems under source control in which source code fragments are modified together in some time frame. When topic models are applied to software systems, latent topics emerge from code fragments. However, it is not yet known what these latent topics mean. In this research, we analyse software maintenance history, and show that latent topics often correspond to code fragments that are maintained together. Moreover, we show that latent topic models can identify such co-maintenance relationships even with no supervision. We can use this correlation both to categorize and understand maintenance history, and to predict future co-maintenance in practice. The relationship between co-maintenance and topics is directly analysed within changelists, with respect to both local pairwise code fragment similarity and global system-wide fragment similarity. This analysis is used to evaluate topic models used with a domain-specific programming language for web service similarity detection, and to estimate appropriate topic counts for modelling source code. / Thesis (Ph.D, Computing) -- Queen's University, 2012-04-30 18:16:04.05