Reference works are for example encyclopaedias, lexicons, dictionaries or manuals. They contain information in compressed, mostly alphabetical order.
Trier UAS: You will normally find printed editions as "not borrowable" on the shelf at the beginning of the respective classification (Examples: "A 01/..." = Reference works on architecture, "B 01/..." = reference works on civil engineering etc.). Electronic editions can be found on the DVD servers (PCs) at the back of the information offices.
first overview of a topic
search for individual data.
Library catalogues are directories of the media that are available in one or more libraries. They indicate the location of the individual media within the library.
supra-regional library union catalogues and meta catalogues: extensive search in the stocks of various libraries, e.g. search via the KVK Karlsruher Virtual Catalogue (meta search for books in all libraries in Germany + search in bookstores + search in worldwide library catalogues).
Specialist databases (bibliographic research):
Specialist or subject databases record the literature production, e.g. on a specific subject area, independent of the availability in the library itself.
In contrast to library catalogues, these databases usually also list works that have been published as component parts, e.g. articles from journals or individual book chapters in collective works with several authors.
Subject databases are usually licensed. The Trier UAS pays these license fees for some subject databases so that you have free access.
Is the worldwide, public computer network. It offers a wealth of information of all kinds and qualities and is mostly used via search engines or web catalogues. It also offers link collections or specialist portals that systematically list selected general and subject information resources. (Examples of "virtual subject libraries" on the library website: Research > Research portals).
However, contents of specialist databases (as they are usually subject to licensing) are often not found (keyword: Deep Web).