  Software engineering is knowledge-intensive and requires software developers
to continually search for knowledge, often on community question answering
platforms such as Stack Overflow. Such information sharing platforms do not
exist in isolation, and part of the evidence that they exist in a broader
software documentation ecosystem is the common presence of hyperlinks to other
documentation resources found in forum posts. With the goal of helping to
improve the information diffusion between Stack Overflow and other
documentation resources, we conducted a study to answer the question of how and
why documentation is referenced in Stack Overflow threads. We sampled and
classified 759 links from two different domains, regular expressions and
Android development, to qualitatively and quantitatively analyze the links'
context and purpose, including attribution, awareness, and recommendations. We
found that links on Stack Overflow serve a wide range of distinct purposes,
ranging from citation links attributing content copied into Stack Overflow,
over links clarifying concepts using Wikipedia pages, to recommendations of
software components and resources for background reading. This purpose spectrum
has major corollaries, including our observation that links to documentation
resources are a reflection of the information needs typical to a technology
domain. We contribute a framework and method to analyze the context and purpose
of Stack Overflow links, a public dataset of annotated links, and a description
of five major observations about linking practices on Stack Overflow. We
further point to potential tool support to enhance the information diffusion
between Stack Overflow and other documentation resources.
