John Favaro, Intecs Sistemi
The tremendous success of the World Wide Web, and the increasing use of WWW front-ends to library catalogs and other information systems has caused decision- makers to question whether the investments required to establish additional Z39.50 services are still warranted. Meanwhile, the increased versatility of the 1995-version of the Z39.50 protocol - which enables it to provide powerful services outside of the strictly bibliographic application domain - leads information specialists to wonder where the WWW and Z39.50 fit together in the evolving information infrastructure.
The Web is an ideal vehicle for organizations that are "vertically integrated," that is, which are owners of content that they can present to the user in a structure of their own choosing. That is why many media and entertainment companies are showing a great interest in the Web today. But when users must actively search the Web for information across organizations, they encounter a sea of largely unstructured data.
The library community has much to offer in the way of providing structure to information resources on the Internet. The Z39.50 standard is a concrete representation of this fact. Currently the search engines and indexes of Web resources suffer from the same weaknesses as the interfaces to library systems. No two are alike, and there is no general way to make structured use of the data that they return. With the current growth of the Web, the search engines are becoming increasingly important - a significant portion of the Web community now spends more time looking at search engine output than on any other type of Web page. However, it may eventually become impossible for any one organization to index everything in a useful way. We will need more well-structured access methods to allow searching across multiple indices. Here the power of Z39.50 as a true, mature information retrieval protocol becomes evident.
Z39.50 specifies an abstract information system with a rich set of facilities for searching, retrieving records, browsing term lists, etc. At the server side, this abstract system is mapped onto the interface of whatever specific database management system is being used. The communication taking place between the server and the client application is precisely defined. The client application is unaware of the implementation details of the software hiding behind the network interface, and it can access any type of database through the same, well-defined network protocol. On the client side, the abstract information system is mapped back onto an interface which can be tailored to the unique requirements of each user: a high-school student may require a simple, graphical interface with limited functionality, while an information specialist may need a complex, highly configurable information retrieval engine. Finally, casual users may prefer an interface which blends in smoothly with their word processor, database software, or, indeed, WWW browser.
In summary, the essential power of Z39.50 is that it allows diverse information resources to look and act the same to the individual user. At the same time, it allows each information system to assume a different interface for every user, perfectly suited to his or her particular needs.