  Web search is among the most ubiquitous online activities, commonly used to
acquire new knowledge and to satisfy learning-related objectives through
informational search sessions. The importance of learning as an outcome of web
search has been recognized widely, leading to a variety of research at the
intersection of information retrieval, human computer interaction and
learning-oriented sciences. Given the lack of explicit information,
understanding of users and their learning needs has to be derived from their
search behavior and resource interactions. In this paper, we introduce the
involved research challenges and survey related work on the detection of
learning needs, understanding of users, e.g. with respect to their knowledge
state, learning tasks and learning progress throughout a search session as well
as the actual consideration of learning needs throughout the retrieval and
ranking process. In addition, we summarise our own research contributing to the
aforementioned tasks and describe our research agenda in this context.
