The W3C Open Annotation Community Group's Open Annotation (OA) Data Model is emerging as a standardized Web Annotation Data Model. We argue that a friendly interactive visual user interface for OA Data Model based annotation tools, which is largely based on an effective user interface model, plays an essential role in the usability of the tools. In this paper we propose an Interactive Visual User Interface Model for Open Annotations (or simply IVUIM4OA), which allows the annotating user to dynamically transform OA data into a visual representation and to interactively manipulate the visual objects to modify the OA data or produce new one. IVUIM4OA is an adaptation of a generic information visualization model, the Data State Reference Model, for the specifics of the visualization of OA data; it is further extended with view operators that enable the user to interact with the visual objects. We implemented a prototype multimedia annotation tool on the basis of IVUIM4OA and conducted case study experiments with the prototype tool. The implementation and experimental results show that the proposed IVUIM4OA is feasible and works well with the OA Data Model, in such a way that the annotating user can obtain a better understanding of and more intuitive interaction with the annotation data.

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The W3C's Media Fragments URI 1.0 specification provides for a media-format independent, standard means of addressing media fragments on the Web using Uniform Resource Identifiers (URIs). Thus, a key requirement is for the User Agent (UA) to efficiently retrieve media fragments identified by URIs from the regular media server over the HTTP protocol. This paper addresses the issue of how to construct a Media Fragment URI aware UA. We propose an approach for achieving such a UA, focusing on fully indexable container formats. Our approach consists of a set of algorithms capable of performing URI-based media fragment retrieval. Algorithm implementation and experimental results show that our approach is achievable and is able to greatly reduce time and bandwidth costs compared to the traditional approach of downloading the entire media resource.

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