The ADS and ESIS both are the result of a major development effort. When they were made available to the astronomical community in 1993, they were state-of-the-art distributed systems for the search, retrieval, reduction and analysis of astronomical data. It seems that NASA and ESA considered these systems mainly as research and development projects, because after being operational for only two or three years, the parts of the ADS and ESIS systems, relying on dedicated client-server systems with their specific graphical user interfaces, will be closed down. Only the pace at which this will happen differs from within one year for ESIS, to several years (?) for the ADS.
The ADS and ESIS services will in the future be provided through the general purpose network information system World Wide Web, employing the hypertext client-server system on which the WWW is based. But particularly in the case of ESIS, where parts of the system will be transferred to other organizations and institutes, it remains to be seen whether the full functionality will, or even can, be provided in the same, or at least a very similar, way.
It is needless to say that these developments do not serve to increase End-User confidence in network information systems. End-Users are interested in continuity and stability of services, otherwise they will not invest time and effort in getting acquainted with a particular system and in learning how to use it.