History of the alSurface shader
The “al” in from the alShaders refers to Anders Langlands, a VFX sequence supervisor currently at Weta Digital, who wrote a series of shaders for Arnold. Anders’ motivation was to implement production shaders for Arnold that he felt fit the VFX world’s needs beyond what Arnold provided natively. One of the most important shaders he wrote in the group is the alSurface shader. Also known as an uber-shader, this shader allowed the user to recreate most surfaces including, solids, metal, transparent, reflective, and even Sub Surface Scattering such as skin.
Here is a representation of the entire alSurface uber-shader in Maya: