It is the target of this special issue to collect and report on recent work that aims at narrowing the large disparity between the low-level descriptors that can be computed automatically from multimedia content and the richness and subjectivity of semantics in user queries and human interpretations of audiovisual mediathe so-called Semantic Gap.
Research in this area is important because the amount of information available as multimedia for the purpose of entertainment, security, teaching or technical documentation is overwhelming but the understanding of the semantics of such data sources is very limited. This means that the ways in which it can be accessed by users is also severely limited and so the full social or economic potential of this content cannot be realised.
Addressing the grand challenge posed by the Semantic Gap requires a multi-disciplinary approach and this is reflected in recent research in this area. Thus, by its very nature, this special issue is targeting an interdisciplinary community. For example, multimedia researchers who deal with signal processing, computer vision, pattern recognition, multimedia analysis, indexing, retrieval and management of 'raw' multimedia data are increasingly leveraging methods and tools from the Semantic Web field by considering how to enrich their methods with explicit semantics. Conversely, Semantic Web researchers consider multimedia as an extremely fruitful area of application for their methods and technologies and are actively investigating how to enhance their techniques with results from the multimedia analysis community. A growing community of researchers is now pursuing both approaches in various high-profile projects across the globe. However, it remains difficult for both sides of the divide to communicate and learn from each other. It is our hope that this special issue will go some way towards easing this by presenting recent state-of-the-art results from both communities.
To provide an outlet and to improve communication and collaboration between the two fields this special issue on "Semantic Multimedia" is actually a double special issue brought forward by Elsevier's Journal of Web Semantics as well as by Springer's Multimedia Tools and Applications. Contributions were sought from both communities and for both journals in a joint call. The 37 papers submitted to the joint special issue demonstrate the large interest in Semantic Multimedia. Only 9 of these papers met the rigorous standards of the two journals and were accepted. We thank all authors for their contributions, as they have exerted great enthusiasm for the research topic and have exposed interesting research -sometimes at early stages of development -that will bear plenty of fruit over the next few years. We also thank all reviewers, from both