Covenant Data Layer Scale, The
Image from Bernd Helfert
Created by virch researchers of the Covenant server at Black Point, the CDL scale was made for the analysis of virtual worlds, and the virtual entities which inhabit them. The CDL scale holds that there are three layers of existence in most virchs; the code, the shell and the sphere. Each previous layer is postulated to be a prerequisite for any of the later layers. Various other stats such as user-friendliness and complexity derive partly from the amount of layers. The CDL scale is not the best known or most widely used of the scales used to display layers, however it is one of the most generic. One major limitation from a software engineers point of view, is that it solely focuses on the software side of the equation, completely ignoring any influence that hardware might have.
1st layer; the Code: The code itself, is the very basic of any computer software. Though the code may react to input, and almost always produce output, it has no interface with which virchers can interact. Any life that may exist in 1st layer systems, are almost exclusively limited to datacology consisting of avatar-less alife.
2nd layer; the Shell: The shell is an interface with which a virtual may interact directly with the code, inputing data and commands, as well as retrieving data. The shell may have a simple (or even elaborate) graphical or virtual interface, but it is purely a interface. Virchers cannot live in the shell, but may contact it through interfaces in the sphere. The 2nd sphere is dominantly lifeless, though some datacologies in the 1st layer interact solely with 2nd layer code.
3rd layer, the Sphere: The sphere is the virtual, interactive, interface which virchers inhabit. No system is truly a virch, unless it possesses all three layers. In some virchs the 2nd layer may be inaccessible to the residents, but many virchs allow access to the shell through various means, while restricting the commands that most virchers can put into the shell. The shell is the location of the prime part of all life, especially sentient and sophont life. A small proportion of virchs have highly abstract datacologies in the sphere, while many others have rich virchologies instead.