  Well established libraries typically have API documentation. However, they
frequently lack examples and explanations, possibly making difficult their
effective reuse. Stack Overflow is a question-and-answer website oriented to
issues related to software development. Despite the increasing adoption of
Stack Overflow, the information related to a particular topic (e.g., an API) is
spread across the website. Thus, Stack Overflow still lacks organization of the
crowd knowledge available on it. Our target goal is to address the problem of
the poor quality documentation for APIs by providing an alternative artifact to
document them based on the crowd knowledge available on Stack Overflow, called
crowd cookbook. A cookbook is a recipe-oriented book, and we refer to our
cookbook as crowd cookbook since it contains content generated by a crowd. The
cookbooks are meant to be used through an exploration process, i.e. browsing.
In this paper, we present a semi-automatic approach that organizes the crowd
knowledge available on Stack Overflow to build cookbooks for APIs. We have
generated cookbooks for three APIs widely used by the software development
community: SWT, LINQ and QT. We have also defined desired properties that crowd
cookbooks must meet, and we conducted an evaluation of the cookbooks against
these properties with human subjects. The results showed that the cookbooks
built using our approach, in general, meet those properties. As a highlight,
most of the recipes were considered appropriate to be in the cookbooks and have
self-contained information. We concluded that our approach is capable to
produce adequate cookbooks automatically, which can be as useful as manually
produced cookbooks. This opens an opportunity for API designers to enrich
existent cookbooks with the different points of view from the crowd, or even to
generate initial versions of new cookbooks.
