Abstract
Mercury is a federated metadata harvesting, data discovery and access tool based on both open source packages and custom developed software. Though originally developed for NASA, the Mercury development consortium now includes funding from NASA, USGS, and DOE. Mercury supports the reuse of metadata by enabling searching across a range of metadata specification and standards including XML, Z39.50, FGDC, Dublin-Core, Darwin-Core, EML, and ISO-19115. Mercury provides a single portal to information contained in distributed data management systems. It collects metadata and key data from contributing project servers distributed around the world and builds a centralized index. The Mercury search interfaces then allow the users to perform simple, fielded, spatial and temporal searches across these metadata sources. One of the major goals of the recent redesign of Mercury was to improve the software reusability across the 12 projects which currently fund the continuing development of Mercury. These projects span a range of land, atmosphere, and ocean ecological communities and have a number of common needs for metadata searches, but they also have a number of needs specific to one or a few projects. To balance these common and project-specific needs, Mercury's architecture has three major reusable components; a harvester engine, an indexing system and a user interface component. The harvester engine is responsible for harvesting metadata records from various distributed servers around the USA and around the world. The harvester software was packaged in such a way that all the Mercury projects will use the same harvester scripts but each project will be driven by a set of project specific configuration files. The harvested files are structured metadata records that are indexed against the search library API consistently, so that it can render various search capabilities such as simple, fielded, spatial and temporal. This backend component is supported by a very flexible, easy to use Graphical User Interface which is driven by cascading style sheets, which make it even simpler for reusable design implementation. The new Mercury system is based on a Service Oriented Architecture and effectively reuses components for various services such as Thesaurus Service, Gazetteer Web Service and UDDI Directory Services. The software also provides various search services including: RSS, Geo-RSS, OpenSearch, Web Services and Portlets, integrated shopping cart to order datasets from various data centers (ORNL DAAC, NSIDC) and integrated visualization tools. Other features include: Filtering and dynamic sorting of search results, book- markable search results, save, retrieve, and modify search criteria.