IT Baseline Protection Manual - The Information Warfare Site

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9.2 Databases
Description
Database systems (DBS) are commonly accepted computeraided
techniques of organising, generating, manipulating and
managing large amounts of data. A database system consists
of the database management system (DBMS) and a certain
number of databases. A database is a collection of data
representing facts on a specific application in the real world.
The DBMS acts as an interface between users and the
database, allowing efficient and centrally monitored access to data, and ensuring the pemanent
availability of this data.
Database management systems now form an indispensable part of IT applications. Without a DBMS,
it would not be possible to manage the vast amounts of data which need to be collected, processed and
evaluated. The concept of a DBMS is based on a particular database model. The most important
database models are described in the following:
Hierarchical database model
This is the oldest existing variant, also regarded as the database model of the first generation. This
database model is structured like a tree. The nodes and leaves in this structure represent the files. A
node or leaf has exactly one predecessor, and data is always accessed sequentially. The access routes
are determined by the tree structure (and file structure respectively).
Relational database model
The relational database model involves strict separation between the data and the methods of accessing
it. The data is stored in the form of tables, where each row represents a data record (also termed tupel)
and each column represents an attribute of the data record. Tupels can be related to other tupels in
different tables, which is marked by a corresponding relationship. As opposed to the hierarchical
model, the relational database model does not impose any restrictions on access to data.
SQL (Standard Query Language), standardised by the ISO, is the database language provided with all
relational database systems.
Object-oriented database model
Object-oriented database models are an extension of classical database models and involve an objectoriented
(OO) technique. In this case, objects with similar attributes are grouped into classes which, in
turn, can be assigned class hierarchies. Only defined methods can be used to modify the objects, the
inheritance of methods and attributes playing a key role in object-oriented design. Standard data types
such as "Integer" and "Character" can be supplemented with type constructors allowing the definition
of complex values.
This chapter only provides a treatment of databases based on the relational database model, as it is
currently the most prevalent.
A database system generally provides simultaneous access for different users. It therefore has to
process several user requests (transactions) in parallel and guarantee a distinct level of fault tolerance.
Of central importance are four requirements which are called the ACID-principle:
- Atomicity
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IT-Baseline Protection Manual: Otober 2000