The aim of this master's thesis is to investigate and to explain the concept of Folksonomy in the perspective of knowledge organisation. By creating a conceptual explanation and defining what Folksonomy as a concept consists of, the intent is to establish a basis for evaluating Folksonomy and to discuss what relevance Folksonomy may have in the field of knowledge organisation. By applying a qualitative content analysis a review is performed on how Folksonomy is perceived and discussed in a selection of articles written on the subject. Employing the theory of classification, subject indexing and bibliographic retrieval, Folksonomy as a method for knowledge organisation is analysed. The practice of tagging in existing systems is also studied.

The purpose of this study is to perform both a quantitative and language philosophical analysis of the folksono-my and the tags in the Stockholm public library catalogue, which together with the Umeå university Folksonomy, and the Folksonomy of the Norrköping public library are the only library folksonomies in Sweden.The purpose of the first part of the study is to perform an analysis of the linguistical structure of the tags in the Folksonomy. To do this a quantitative analysis has been conducted to grammatically categorize and evaluate tags using a method based on Louise Spiteri?s article ?The structure and form of Folksonomy tags: the road to the public library catalogue? and the SAO guidelines. This part of the analysis aims to answer questions like: what characteristics do the tags in the Folksonomy have and in what ways do they separate themselves from subject headings in a controlled vocabulary? Tags were here categorized according to grammatical properties like parts of speech and their social and private characteristics.

The aim for this master?s thesis is to investigate the indexing consistency in a Folksonomy Delicious. This is done by investigating how users construct tags. By applying a semiotic perspective and use analysis of content the occurrences of inflected forms, hyponymy, meronymy and users own tag creations were established. Lancaster?s seven factors is the starting point for the discussion about indexing and the factors that affects it in either a negative or positive way.

The web has evolved much through the years. From being a place where author and reader were clearly distinguished, it now invites everyone to take part in the development of both content and technology. Social services are central in what is called Web 2.0. Wikis, blogs and folksonomies are all examples of how the users and their communities are key to the development of services. Collaborative writing, tags and API:s are central.

Image indexing research today is either conducted on a visual attribute level or on a higher semantic level, forming a semantic gap between the two. There is much to gain if research progress from the two fields is combined. Image retrieval using access points in both visual and semantic significations could improve retrieval and bridge the gap. In social media today, images are often the primary communication agent and the number of images on the web is increasing in an uncontrolled way. New and efficient ways to index and retrieve the images are needed.The purpose of this study is to examine if emotions could be a semantic access point for image retrieval and if Folksonomy indexing is useful when searching for images that represent emotions.