The terms that are used by users during tagging have been found to be different from the terms that are used when searching for resources, which represents a fundamental problem for search in tagging based systems. To address this problem, we propose purpose tagging as a novel kind of tagging that focuses on capturing aspects of intent rather than content. By capturing the different purposes a given resource can serve, purpose tags appear useful to mediate between the vocabulary of user intent on one hand, and the vocabulary of contents and tags provided by social software applications on the other. The paper at hand makes the following contributions: 1) It extends the set of known kinds of tags with a novel type and 2) it provides first empirical evidence of the principle feasibility of purpose tagging and its potential to facilitate goal-oriented social search in an exploratory case study. Categories and Subject Descriptors H.3.3 [Information Storage and Retrieval]: Information Sear...