From OpenSCADAWiki
Modularity
In order to achieve flexibility and a high degree of scalability OpenSCADA is constructed in a modular fashion. Tight integration the modules with the core improves the program stability in whole due to repeat of using the well-tuned code. But same process of developing of self code of the modules OpenSCADA imposes greater responsibility — possible errors introduce an element of instability into the program. The ability to create distributed configurations smooths this danger.