The European Space Information System (ESIS) project was initiated in 1988 as a service for homogeneous access to heterogeneous databases on the network.
The project pre-dated the World Wide Web, which immensely pushed technology in 1993 to allow homogeneous access to data.
Initially, the ESIS project was to link databases of the European Space Agency together with centres of excellence that included the Centre de Données astronomiques de Strasbourg and its SIMBAD service, the European Southern Observatory and the Canadian Astronomical Data Centre (CADC), as well as the Rutherford Appleton Laboratory for Space Physics data [1] The outcome of the project yielded a set of applications to browse catalogues, access images, spectra and lightcurves, as well as access to bibliographic information.
Having been a pioneer project in its days, many of the original concepts used then (such as catalogue browsing, searching in an area of the sky) were later embedded in other astronomical data services worldwide.
[2] In recent years, the ESIS concept, which was decades ahead of its time, is reflected in the ESA Sky tool [3] encompassing over 75 space missions and multiple data archives giving a unified access to multiple wavelength astronomy data.