Data described within the ADL domain are made accessible via HTTP and Z39.50 servers. Primary access to ADL will be from WWW browsers connecting to the Alexandria Web server. Z39.50 clients will also be able to contact the Alexandria Z39.50 service. Under the direction of the FGDC, federal and state governments are setting up servers that support a well-known set of metadata elements from the FGDC metadata standard. Through these standard data elements, broadcast queries can be made from the ADL server, using Z39.50, to other servers and a composite set of relevant documents from many sites can be built and served to a client.
In addition to relying on Z39.50 to access other servers we envision that existing Z39.50 clients, primarily on-line systems in the library community, will benefit from gaining direct access to ADL's metadata and data stores. Z39.50's standard queries, presentation fields, and search and retrieve protocols provide time-tested interoperability elements that we cannot ignore.