Various XML-based approaches aimed at representing compound digital assets have emerged over the last several years. Approaches that are of specific relevance to the digital library community include the Metadata Encoding and Transmission Standard (METS), the IMS Content Packaging XML Binding, and the XML Formatted Data Units (XFDU) developed by CCSDS Panel 2. The MPEG-21 Digital Item Declaration (MPEG-21 DID) is another standard specifying the representation of digital assets in XML that, so far, has received little attention in the digital library community. This artic le gives a brief insight into the MPEG-21 standardization effort, highlights the major characteristics of the MPEG-21 DID Abstract Model, and describes the MPEG-21 Digital Item Declaration Language (MPEG-21 DIDL), an XML syntax for the representation of digital assets based on the MPEG-21 DID Abstract Model. Also, it briefly demonstrates the potential relevance of MPEG-21 DID to the digital library community by describ ing its use in the aDORe repository environment at the Research Library of the Los Alamos National Laboratory (LANL) for the representation of digital assets.

In recent years, the number of organizations making digital information available has increased dramatically. This evolution has encouraged the development of various approaches to represent complex digital objects. Approaches that are of specific relevance to the digital library and archiving community include the Metadata Encoding and Transmission Standard (METS), the Content Packaging XML Binding of the Instructional Management System (IMS) project, and the Sharable Content Object Reference Model (SCORM). The MPEG-21 Digital Item Declaration (MPEG-21 DID) is yet another packaging approach that, so far, has received little attention in the digital library community. The primary goal of this article is to offer a method to compare these packaging approaches in the context of the needs of the digital library community and the rising digital preservation programs. The contribution of this paper is the definition of an integrated reference framework, based on both the ISO OAIS Reference Model and a set of additional significant properties that affect the quality, usability, encoding, and behavior of complex digital objects. This article also gives a brief insight into MPEG-21 DID and examines its potential relevance by showing the results obtained from applying the proposed reference framework.

This review is a summary of the state-of-the-art for those who have not been intimately dealing with the evolution of digital archives. At the same time this survey will be a useful resource and starting point for archivists, librarians and technicians, who are becoming involved in institutional digitization projects. It presents a brief overview of what is meant by a digital library and a digital archive, and how archival collections can be described. It expresses briefly the different approaches to collections and their descriptions and suggests that a consistent approach to descriptions at collection and item level is an

In 1840 the Belgian industrialist Charles-Henri Marcellis (1798-1864) and his partner V. Duval developed a cast-iron girder bridge to replace traditional arch or suspension bridges. When 3 years later the town council of Ghent decided to connect the new railway station with the old Saint-Peter's quarter, two areas that were divided by the Scheldt River, it became its first Belgian test. The 20-meter long 'Marcellis Bridge' as it would soon be called, consisted of two pairs of castiron pierced plates, each pair forming a box girder and serving as a parapet. The trump card of this bridge was its straight line that did not impede river navigation nor did it create a 'mountain' for horses and coaches crossing the bridge. When looking closely at the development of Marcellis' bridges in books, plans and building permits one notices a striking resemblance between his projects and Robert Stephenson and William Fairbairn's successive bridge designs in England. Both the Belgians and the English started with cast-iron girders in the 1830s-40s, developing into more complex box and tubular bridges in the 1840s-50s. A clear path of knowledge transfer is not yet identified, but dating the different designs makes it clear that Marcellis was inspired by England's trial and error testing of this new and also momentary type of bridges. In the second half of the 19 th century these bridges would be built using wrought iron and steel due to cast iron's lack of tensile strength and ductility, and its risk of fatigue.

During recent years, the number of organizations making digital information available has massively increased. This evolution encouraged the development of standards for packaging and encoding digital representations of complex objects (such as a digital music albums or digitized books and photograph albums). The primary goal of this article is to offer a method to compare these packaging standards and best practices tailored to the needs of the digital library community and the rising digital preservation programs. The contribution of this paper is the definition of an integrated reference model, based on both the OAIS framework and some additional significant properties that affect the quality, usability, encoding and behavior of the digital objects.