Hjørland has emphasized in many papers that any work in library and information science cannot be "atheoretical", but should be based explicitly on some theoretical approach. He has classified four main approaches to LIS: empiricist, rationalistic, historical-hermeneutical and pragmatical, the last two of which he considers to be more valuable.
Hjørland's domain analysis is an attempt at a comprehensive theory that can be applied to information science. Its main premise is a set of analytical tools that can be applied in subsets or as a whole to in order to study the effects of different social, epistemological, and cultural fields on the theories of information science. Thus organization is applied in relation to the different domains from which it emanates and is consumed. Rather than studying the user in this case, the domain or environment is the main focus of the theory. Individuals are seen as members of distinct cultures or domains and their subsequent document systems. Similar to domain analysis, concept theory aims to create a theory of concepts which may be applied to knowledge organization systems by analyzing conceptual semantic relationships. Different theories of concepts, i.e., how users interact with information, shape interaction with information in three specific aspects: bibliometrics, information literacy, and knowledge organization. This theory indicates that concepts are definitions of the world created according to one's inclinations and ideas; they cannot exist in isolation from the interests that created them. Hjørland argues that the theory is best understood through historicists and pragmatic interpretations, i.e., cultural influences on concepts best describe their meaning as well as pragmatic changes to concepts to allow humans to adapt and change certain concepts. Thus, concepts evolve with human practices. Hjørland's work has been classified as social constructivism. Indeed, he cites own work in domain analysis as "socio-cognitive", that is, the study of the effects of a culture on individuals, and their information artifacts.
Wikipedia
In recent years, Hjørland has done research on Wikipedia as a part of establishing an information science-grounded kind of source criticism. He has written research articles about the reliability of Wikipedia. In one them, he compares a Wikipedia article about a breast cancer controversy to an article in Encyclopædia Britannica and two Danish encyclopedias. As a part of the research, Hjørland has edited Wikipedia himself, making contributions to several articles related to information science.
