When catalogs collide: A mashup of the bibliographic records from New Zealand´s National Bibliography and the HathiTrust

In this article we present work done developing an interactive comparison tool for large-scale catalogs using the general purpose open source digital library toolkit, Greenstone. The two catalogs selected to demonstrate the approach were the Bibliographic Records from New Zealand´s National Bibliography and the HathiTrust. With Greenstone´s triple-store extension activated, the two collections were ingested to form two Greenstone collections. Next, an interactive visualization tool was developed within the digital library´s presentation layer to allow users to explore the two collections, comparing fields from the two collections and producing a variety of visualizations. The required interactivity was accomplished using AJAX calls to the Greenstone triple-store, further supported by the use of Javascript libraries for the presentation of the retrieved data in both visual and spreadsheet forms.