On the Importance of “ Who Tagged What ”

Adaptive systems can be used to help people find their way through large amounts of information by taking into account the content itself and opinions of other people. Annotations that describe content are important in this process as is generally recognized. What is less obviously stated so far is that not only the annotations themselves, but also knowledge of who provided the annotations can be relevant for adaptive systems. Annotations can namely be regarded as an opinion of the annotator, which can only be valued if one knows who provided it. Various sources of annotations and the importance of knowing who provided an annotation are described using real-world cases. This is followed by the introduction of various ways that adaptive systems can use the knowledge of “who tagged what” when helping people find their way through large amounts of information.