Cisco config checker

Is there such a thing as a Cisco config checker, to allow off-line editing of Cisco configs and check them before they're uploaded to the router? Preferrably something that could be used in a Web/Unix environment as a filter. If not, does anyone know of a source for a complete definition of Cisco configuration language, in some kind of standardized format, so I could possibly generate a config-checker myself? Thanks. Pete.