A typical software product build with Yocto Project makes use of several different metadata layers. These layers may be maintained by hardware manufacturers, software/service companies, or individual hobby developers. Naturally there is some variation in layer quality and compatibility - some layers play well with each other while others are in practice mutually exclusive. For example, misbehaving layers may force the selection of particular machine or distro or make unwanted changes to recipes defined in other layers. This can result in broken builds (often with confusing error messages) or subtle runtime errors and crashes which may be difficult to debug.