FullPliant is an operating system based on, and written in, Pliant, by Pliant's author. The language and OS form an elegant integrated and highly flexible whole.
Pliant's core advantage is its ability to allow several levels of programming, from low-level instruction lists, to high-level expression manipulation, in one unified environment, and syntax as needed. Thus, it stresses the "compiling rules" definitions using "meta" functions (functions run at compile time to compile an expression) and "active types" (types having their own compiling scheme).
New application services were then integrated at language level (examples: scheduling primitives, database management), thus bridging usual gaps between applications. From this viewpoint, a program is seen as a set of libraries, or even as a language extension, possibly introducing its own syntax changes.
FullPliant has been used in an industrial context since 2000. The transparent integration in the dynamic page extension of signature and right verification mechanisms clearly demonstrates that security can be achieved without unneeded additional programming complexity.