In the 80's, dedicated computer archives and databases, accessible remotely (when the networks allowed), were the appropriate answer to the data retrieval problem. Later on, in order to face the diversity and complexity of access to data for the astronomers as part of their research work, integrated information systems started to build up gradually: examples are the ADS in the U.S. and the European Space Information System (ESIS) in Europe.
A key lesson from these experiences is that the data have to reside and be maintained at the same place where the expertise is located: i.e. as close as possible to the data providers, and generally first users, who are able to understand and process the raw data, and provide the routines for producing final data in physical units - a process which sometimes implies several years of iterative improvements.
However, the scientific teams are generally reluctant to devote time, manpower and money in the different aspects of data distribution to a wider community (documentation, homogenization, building of friendly user interfaces, etc.).
At the same time, the growing complexity of data systems, implies a change of concepts. The scientist has not only to manipulate data, but information: observational data, but also documentation about the data, knowledge about the instruments, calibrations, bibliographical references of published results, cross-references to other datasets, etc. Pointers and links between these different pieces of the same puzzle have to be constructed.
The recent developments of the World-Wide Web have brought interesting answers to these problems, by providing altogether
The astronomical community showed a very early interest to the World Wide Web and several dozen WWW servers were already available in mid-1993, several hundreds in mid-1994, one thousand at the end of 1994. The astronomical community was ready to jump onto the Web, because of its familiarity with the international collaboration through the data networks, and its computer infrastructure.
A very good way to observe this incredible explosion of astronomical WWW servers is to connect to the AstroWeb, and browse through the different categories: observing resources, data resources, publication-related resources, people-related resources, organizations, software resources, etc.
Using your favorite WWW browser, you can display the corresponding lists of resources, find a title and eventually a brief summary of the resource: click here and you are witnessing the scientific activity of an astronomical department in Finland; click there and you find the observing schedule on Mauna Kea...
The result of such ``Web surfing'' may be surprising, exciting, or exotic. It may also be disappointing or upsetting when the ``work in progress'' sign regularly appears on each and every page, and when promising anchors point to empty pages. This is probably the danger of such an explosion: there is the risk to be flooded with documents of low interest. In the published scientific literature there is a way to solve that: namely the refereeing process. It brings the guaranty that at least somebody else has reviewed the document, and had the opportunity to make a critical review, and to suggest improvements. This is not the case with most of the documents on the Web.
Obviously, the astronomical community will have to organize itself in order to answer properly this challenge, and derive the necessary rule, etiquette, and procedures, for ensuring the highest possible quality standards for on-line information.
The book ``Information & On-line Data in Astronomy'' reflects the important changes mentioned above. When we edited the book ``Databases & On-line Data in Astronomy'' (M. A. Albrecht & D. Egret, Eds, Kluwer Acad. Publ. 1991) we had envisaged the need of editing an updated version a few years later.
However when the time of volume 2 (the present book) arrived, it was obvious that the technological changes imposed changes in the format of the book (it is now accompanied by an on-line hypertext complementary version) as well as in the title: Information handling is now becoming increasingly important, together with data handling, in the scientific process.
The selection of data holdings and information systems presented here, cannot pretend to be exhaustive. It should be noted that we made a review of the of services presented in the first volume, and those of which the scientific contents have not dramatically changed, are not present in this volume. The reader is asked to refer in this case to the first volume. The updated information about access to these services is available in the on-line version.
The on-line complement of the book includes summary descriptions of the data systems presented here (as well as those presented in ``Databases & On-line Data in Astronomy''), together with the complete access pointers (these will be kept up-to-date) and, when available, ready-to-use hyperlinks to the original data systems (either WWW, ftp or telnet services).
In this book, the reader will also find, at the end of most of the chapters, a section called ``Access Pointers'' which gives WWW, ftp or telnet addresses for the decribed services.
The book starts with a general discussion of the on-going information (r)evolution. The next chapters present data archives from a number of current space or ground-based experiments (from Compton GRO to COBE). The book continues with chapters presenting the status of several databases (NED, LEDA, BDA), data centers, facilities and information systems (HEASARC, CDS, ADS, ESIS), yellow-page systems (Star*s Family), and library information services.
The last chapters deal with important related issues: how to make information available on the network, networking and information retrieval, data storage technology, and a brief description of the convention used by NED and SIMBAD for bibliographic reference coding.
The full list of authors with their affiliation and address, a table of acronyms, and a subject index can be found at the end.
This work includes a series of clear and up-to-date descriptions of available data systems world-wide, together with their scientific context and motivations. It would not have been possible without the very kind contributions of the authors of the individual chapters, mostly key persons from each project: thanks again to all of them for their enthusiasm and efficiency.
This book should help the reader (astronomer, librarian, computer engineer) to trace his/her way among the jungle of existing on-line astronomical services. It is also meant to encourage the creation of new information services, thus broadening the capacity of the scientific community to observe and understand the universe.
Strasbourg and Garching
February 1995