Greenstone's Digital Library System was chosen as the metadata storage, retrieval, and search engine for UFDC. Greenstone is an open-source
digital library system produced and maintained by the New Zealand Library Project at the University of Waikato. It is promoted by the United Nations to many of our partners in Africa, the Caribbean, and Latin America. Greenstone has two main components, the metadata portion and the
display portion. While the metadata and indexing portion is strong, we felt that the display portion did not provide some of the functionalities we required. As a result, we chose to
utilize only the metadata portion of Greenstone. All the bibliographic data ultimately resides in Greenstone 2.60 running under Linux.
We chose to build a multi-tier architecture with a custom presentation layer. Greenstone forms the foundation of UFDC. A presentation layer provides access to the web user. Work began on
creating this layer in C#, utilizing ASP.net. The presentation layer will read all bibliographic data from Greenstone and interact with Greenstone in real-time to perform searches. The Greenstone server
will continue to serve both the data and the image. However, the user will interact with the presentation layer outside of Greenstone.
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| Figure 1: Basic Architecture with Greenstone, Presentation Layer, and User |
There are several advantages to this architecture, besides total control over look and feel. This provides for platform independence. Greenstone could be removed from the data layer and a variety of
other digital library managament systems could be used. We can build a hierarchical collection structure with collection groups, collections, and subcollections.
Using this architecture will also allow us to store session state and develop user portfolios, should we decide to do so in the future. This architecture can read data from a variety of sources besides
Greenstone, and allow the data and images to appear under the same interface. This provides for a continuous look and feel for the users regardless of the source of the images and data.
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| Figure 2: Architecture with multiple data and image sources |
