In this paper, we describe our experience implementing some of classic
software engineering metrics using Boa - a large-scale software repository
mining platform - and its dedicated language. We also aim to take an advantage
of the Boa infrastructure to propose new software metrics and to characterize
open source projects by software metrics to provide reference values of
software metrics based on large number of open source projects. Presented
software metrics, well known and proposed in this paper, can be used to build
large-scale software defect prediction models. Additionally, we present the
obstacles we met while developing metrics, and our analysis can be used to
improve Boa in its future releases. The implemented metrics can also be used as
a foundation for more complex explorations of open source projects and serve as
a guide how to implement software metrics using Boa as the source code of the
metrics is freely available to support reproducible research.Comment: Chapter 8 of the book "Software Engineering: Improving Practice
through Research" (B. Hnatkowska and M. \'Smia{\l}ek, eds.), pp. 131-146,
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