An Extensible Database System

Secondo is an extensible database system supporting especially non-standard applications. Designed at the FernUniversität in Hagen, Secondo is a platform for implementing and experimenting with various kinds of data models.

Secondo can be used by groups at universities to pursue and prototype their research ideas for database systems. It can be used in teaching to show students in detail the architecture and implementation of database systems. Additionally, Secondo may be interesting for users in need of a database system able to handle non-standard data types usually not supported by standard systems.

The Secondo system is extensible by algebra modules, using a well defined interface. New data models and data structures together with their operations are integrated into the system in this way. The source code is available and enables the user to access and modify every part of the database system. Secondo comes with a carefully written user manual, programmer's guide and installation instructions.

Objects of an arbitrary type defined in one of the Secondo algebra modules can be stored in a database. The following list shows some of the available algebras:

• Standard-Algebra
  provides simple types like integer, real, bool and string and operations on those types.
  
  
• Relational-Algebra
  contains data types and operations to realize a classical relational database system.
  
  
• Spatial-Algebra
  represents geometrical objects such as points, lines and regions together with spatial operations.
  
  
• Temporal-Algebra
  represents moving objects in databases, e.g. peoples or vehicles and allows one to formulate queries about their movements.
  

Using these algebras, one can determine the names and addresses of all Italian restaurants in Berlin, which have a distance smaller than 2 km to the Brandenburg Gate. Then, the result is presented graphically.

   select [r:name, r:strasse, r:geoData]
   from   [restaurants as r, sehenswuerdpoi as s]
   where  [ s:name="Brandenburger Tor",
            r:art="Italienisch",
            distance(r:geoData, s:geodata) < 2000]