Groups-Users Matching in an Annotation System Using Ontologies (Class Match Measure) Danilo Avola, Paolo Bottoni, Amjad Hawash Dept. of Comp. Science, Sapienza University Rome, Via Salaria 113, Italy (avola, bottoni, hawash)@di.uniroma1.it Figure 1: MADCOW 3-tier Client-Server Architecture. Copyright is held by the author/owner(s). CHItaly 2013, 16-19 September, 2013, Trento, Italy. Abstract Introducing groups to the MADCOW annotation system solves the privacy-collaboration problem for users, but a new challenge emerges for the group joining process in terms of irrelevance, time and effort, for both users and groups’ authorisers. We introduce MADCOW domains and link them to domain ontologies. Users can then use tags derived from ontology terms to synthesize the intent and scope of their annotations. We propose the use of matching measures between domains and users’ annotations as the basis for suggestions of groups to users and of users to groups authorisers. A reduction of the mentioned problems ensues. Author Keywords Annotation; Groups; Joining Process; Ontologies. ACM Classification Keywords H.5.3 [Information interfaces and presentation]: Group and Organization Interfaces. Web-based interaction. MADCOW System MADCOW 1 supports the annotation of (portions of) texts, images and videos with textual content, links to other resources, and user-defined tags [4], through a 3-tier architecture (see Figure 1). Annotations published in 1 Multimedia Annotation of Digital Content Over the Web