Partial Domain Comprehension in Software Evolution and Maintenance

Partial comprehension is a necessity in the evolution and maintenance of very large software systems. The programmers form not only partial comprehension of the code, but also partial comprehension of the application domain. To describe the comprehension process, we introduce ontology fragments and investigate how programmers form, use and extend them before and during concept location; concept location is a prerequisite of code changes. We conducted case studies of concept location in two large systems, Eclipse and Mozilla, that both have more than 50,000 methods. Using grep search and ontology fragments, the programmers were able to locate the concepts after inspecting on average less than 10 methods and operating with ontology fragments of around 14 concepts, a very small fraction of the total.