Online databases are databases which are available “online”, that means remote access by means of data transmission line. These databases are offered as a commercial service by database hosts (computer and information centers with specialization for online services).
Databases referred to in this article are included in the offers of the database host STN ("The International Scientific & Technical Network") and of other database hosts. 

Bibliographic online databases contain the document descriptions of the various types of scientific publications.
A special type from these publications are patent documents. They primarily are offered by special patent databases, but they can also be represented in bibliographic databases.

Virtual super database
A virtual super database is an temporary association of several great databases to a very large complex database. This super database keeps the structures as well as the stored informations of the included single databases.
The retrieval of information in a super database takes place like in a single database.
Retrieval of informations in a super database leads opposite retrieval in single databases to a considerable increase of the retrieval completeness. At the same time it is possible to remove all find duplicates which result from retrievals in different separated data bases. 
The researches  and analyses described in the article were carried out with a super database which contained seven great bibliographical databases with a total volume of 48 million document descriptions.

A Document description in a bibliographic database consists of  formal data, bibliographic data and a content description of the document.

Clusters of databases
STN database clusters contain databases covering the same subject area 
( compare www.stn-international.de/clusters.html ).

Research and development ( R&D )
In the available article the term  "Research and development" also comprises all researches without direct relation to development, for instance pure researches at universities and in other institutions.