As of 22 April 2009 this website is 'frozen' in time — see the current IFLA websites
This old website and all of its content will stay on as archive –
The ZDB contains now 940,000 bibliographic records for serials, to which are attached almost 4.5 million holdings records for all major German (about 4.000) and - so far - a few non-German libraries from neighbouring countries. The cataloguing code used is the German RAK (Regeln für die Alphabetische Katalogisierung), which is ISBD-based and applies the successive entry method: the number of bibliographic records, therefore, is higher than the number of serials registered. (Since we share the successive entry method with AACR, with the ISSN network and with almost everybody in the world, our figures are comparable internationally nevertheless).
The ZDB is open to all types of serials from all periods, from all countries and in all languages, with all non-Roman scipts, however, transliterated according to international or national standards. There are no restrictions: apart from scientific journals, which play the most important role, of course, all sorts of reports of merely local importance, fanzines and whatever may be included, are in fact included, as long as they represent a serial. This lack of restrictions is one of the aspects which leads us directly to the explanation why the ZDB is not only a union catalogue in the traditional sense, is more than just a union catalogue, and is intentionally called a Database:
The participants of the ZDB network input their holdings and every new title not already available in machine-readable form into the database not primarily with the intention to contribute to a national union catalogue, but with the intention to produce, to obtain their own serials catalogue with a minimum of effort, benefitting from the large number of records already in the database, and accepting, that for the few new records they have to contribute themselves, they have to follow the agreed-upon standards of the ZDB.
Under these circumstances it is inevitable that each library is free to input whatever it needs, whatever it wants to have in, or convert to, machine-readable form for its own purposes, as long as it is a serial publication and not a monograph. In the first place, therefore, the ZDB is to be considered an efficient tool for the shared cataloguing of serial publications held in German libraries, using machine-readable data and uniformly applying the same rules and procedures. In a certain sense, the union catalogue function could be called a mere side-effect of these activities, although a very welcome and a very important one, naturally. And, of course, the ZDB would not be a union catalogue at all if the participating libraries would contribute bibliographic records only; if they had not been prepared, from the beginning, to also input their (summary) holdings for the respective titles.
Again, this input of titles and holdings into the ZDB does not happen primarily to feed a union catalogue, but because the fact that holdings data of a certain library are attached to certain biliographic records is a means, is the means, to identify all the titles which are held by a certain library. Starting from these holdings, therefore, the local serials catalogue can be selected from the database and is delivered regularly to the respective library, where the data are integrated into the local OPAC. (Let me add in parentheses that in reality the data are selected mostly under regional aspects and are passed on to regional centres first before they are distributed there to the individual libraries. This is possible because the library identifiers used in Germany for holdings information are structured hierarchically according to regional criteria.)
As you have seen, the holdings are put into the ZDB by the individual libraries to enter, so to say, a claim for the respective title records. As soon as they have done this, they have to take care, also, that the information stays up-to-date. Since their own catalogue, from now on, will be derived, will be downloaded regularly from the national serials database, there is a strong motivation for every library to update their own catalogue data online within the ZDB; a much stronger motivation than can ever be expected to update a union catalogue in the traditional sense, i.e. a union catalogue which is something completely different and existing completely separated from the contributing libraries, and where these libraries are free to supply the union catalogue with information or to leave it.
Updating, of course, is not restricted to holdings; it extends also to bibliographic records. And whereas every library has free online access to its own holdings to update, to amend them, and is also free to input any new bibliographic record needed as long as it is not a duplicate, the ZDB has set up a barrier against any direct modification of existing bibliographic records by the participants. This sort of modification is left to the authentication centre run at the Staatsbibliothek zu Berlin, where every participant may apply, online or however, to have a record updated, amended, or extended. This has been working well for almost 20 years now and, together with the responsibility of the authentication centre for the elimination of duplicate records which have slipped through has been a major means to ensure a coherence of the database which, in all modesty, may be called unrivalled worldwide.
The size of the database, its offer of a bibliographic record for almost every serial in the world, as well as the reliable, efficient and well-functioning organisational concept of the ZDB make it attractive also for libraries outside Germany, particularly for libraries which still have to convert their traditional serials catalogues to machine-readable form. As could be expected, this is the case in many East-European countries where the libraries, by inputting a holdings statement and thereby entering a claim for the respective ZDB records, can easily create their own machine-readable serials files. The ZDB offers this sort of participation and benefit even without the condition to permanently keep and regularly update the data within the ZDB -- although, of course, this would be highly desirable from the point of view of international lending and document supply.
This is another, and my last, aspect which I want to enlarge upon; an aspect which must not be left out in the presention of a union catalogue; since interlending and document supply are not only traditionally but, obviously, also at present and in the foreseeable future, the main task for which union catalogues are made after all. In Germany the ZDB, apart from being distributed on microfiche and on CD-ROM, where everybody can look up where he/she can find, can obtain volume x of Journal y, is part of the online-services offered by our partner institution, the Deutsches Bibliotheksinstitut, and which are called DBI-LINK and SUBITO. In the context of DBI-LINK, the ZDB can be accessed online as a Website, be it by searching the serial titles directly, be it - for the more recent scientific literature - by an approach via the author or title of a particular contribution from the table of contents of thousands of journal issues, all this without charge. In the latter case, only those libraries will be shown to the searcher which actually have the desired volume. The user may then decide where he wants to place his order, taking into account whether he wants the text urgently or not, on paper, as a fax or in electronic form. Online ordering, or rather the following supply of the desired document, has to be paid for, of course.
SUBITO is the more recent service. It is more than just an online ordering service insofar as it has an active supply component. Not only have the participating libraries agreed here on equal fees for the supply of a (medium size) journal article, they have also agreeed on preferring supply in electronic form as the cheapest offer, and they all apply the same equipment, the so-called DOD stations (for document order and delivery) where the ordered documents can be scanned, if necessary, and delivered directly to the requesting individual's home or office PC. (This service, however, is still in its test implementation right now.)