Establishing the value of socially-created metadata to image indexing

There have been ample suggestions in the literature that terms added to documents from Flickr and Wikipedia can complement traditional methods of indexing and controlled vocabularies. At the same time, adding new metadata to existing metadata objects may not always add value to those objects. The potential added-value of using user-contributed (“social”) terms from Flickr and the English Wikipedia in image indexing is compared with using two expert-created controlled vocabularies—the Thesaurus for Graphic Materials and the Library of Congress Subject Headings—without those social terms. Experiments confirmed that the social terms did add value, relative to terms from the controlled vocabularies. The median rating for the usefulness of social terms was significantly higher than the baseline rating, but was lower than the ratings for the terms from the Thesaurus for Graphic Materials and the Library of Congress Subject Headings. Furthermore, complementing the controlled vocabulary terms with social terms more than doubled the average coverage of participants' terms for a photograph. The relationships between user demographics and users' perceptions of the value of terms were also investigated, as well as the relationships between user demographics and indexing quality, as measured by the number of terms participants assigned to a photograph. Participants with more tagging and indexing experience assigned a greater number of tags than did other participants.

► Social terms provided added value relative to terms from TGM and LCSH.
► The median rating for usefulness of social terms was significantly higher than the baseline.
► The median rating was lower than the ratings for the terms from TGM and LCSH.
► Adding social terms more than doubled the average coverage of participants' terms.