Multimedia Metadata and Semantic Management

O ur special issue on multimedia metadata and semantic management presents new research that focuses on contextualized, ubiquitous, accessible, and interoperable services on a higher semantic level. The multimedia metadata description standards—for example, MPEG-7/21—proposed in recent years have added an important aspect to the creation of multimedia content and related semantic management. Most of the standards are tailored to specific application domains. Examples include European Broadcasting Union P/Meta 2.0 for broadcasting; TV-Anytime and Society of Motion Picture and Television Engineers Metadata Dictionary for TV; and MPEG-21 for the delivery chain of multimedia and technical aspects (such as, Exchangable Image File Format, or EXIF). These standards exhibit a different semantic level of detail in their descriptions (from simple keywords to regulated taxonomies and ontologies). Only some of the standards are general purpose, for instance MPEG-7. Recently, the application of Semantic Web technologies to multimedia content has brought forward the use of the Resource Description Framework and Topic Maps for the description of multimedia metadata. Their use might contribute to better interoperability in retrieving multimedia content and is therefore supported by recent standardization efforts in JPEG—that is, the JPSearch initiative for image retrieval (ISO/IEC SC29 WG1 and 24800) and the World Wide Web Consortium Media Annotations Working Group (see http://www.w3. org/2008/WebVideo/Annotations/). To retrieve content interoperable over distributed databases, appropriate middleware technology must be employed. First, we must bridge heterogeneity in metadata description and query languages; second, we must cleverly aggregate and concisely present results to the user; and last, we must provide the security and related access-control techniques according to the multimedia content. Synchronizing the metadata information with the media, and vice versa, is another challenge for effective multimedia management and must be addressed at all levels of the metadata life cycle. This challenge includes dealing with time synchronization as well as synchronized access to streamed and (possibly distributed) stored media and metadata.