From OpenSCADAWiki
OpenSCADA modules are stored within dynamic libraries and each shared library can contain modules of various types. The filling of dynamic libraries by modules is determined by the functional connectivity of the modules itself. Dynamic libraries are hot swappable which allows to update certain parts of the program during the operation. This method of storing of modules' code in dynamic libraries is essential for OpenSCADA, because it is supported by practically all modern operating systems (OS). However, this does not exclude the possibility of developing other methods of storing of the modules' code.