The Digital Library Architecture Reference Model

During the past few years, conceptions, characters, architectures as well as technologies of Digital Library have been widely discussed. However, people find it difficult to enhance the interoperability and scalability when they begin to build actual digital libraries based on the current research. It has become necessary for us to improve the design of existing digital libraries to overcome the two outstanding non-technical problems.Interoperability, including the communication between format-heterogeneous as well as the communication between architecture-heterogeneous resources, is the ability to communicate with the world outside. Therefore, the extensibility of a digital library is dependent on its interoperability. Scalability, which means more new resources and new services, is the ability to develop with the pressure of rapidly progressing technology. A good digital library should be able to communicate with the world outside and to develop itself as well; this is exactly the new rule set by the author to evaluate digital libraries.During the last ten years' evolution of Digital Libraries, a lot of Digital Library architectures have been worked out. They include K-W architecture which is well known for its "handle system", DIENST architecture which uses "collection" to search information, INFOBUS architecture which extends its services from the bottom to top, Warwick framework which introduces the idea of "container", FEDORA architecture which resorts to "content type" to solve interoperability issue, and OAI architecture which uses "filtering gate" to solve the same problem. Each of these architectures has its own advantages and disadvantages as far as the interoperability and scalability are concerned. Based on the analysis on these models, the author presents a new DigitalLibrary architecture that is based on the new evaluation rules. By emphasizing hierarchy and modulation, the author hopes that this new architecture can be referenced by other people.This article consists of four chapters. Chapter one gives a general introduction of Digital Library including its definitions, development history, characters and its relation to traditional libraries. Chapter two introduces six architectures/models of Digital Library in detail and analyzes its advantages and disadvantages with regards to the interoperability and scalability. Chapter three outlines five key factors and six principles while designing the architecture of the digital library. Chapter four summarizes all the digital library architectures referenced in this article. Based on the analysis of the main requirements in building a digital library, the author presents a new architecture of Digital Library with four characters.